Extra Tranny cooler not sufficient - what next ?

[truck2trail]

I had a Tru-cool 9.5”x11”x0.75” installed in October 2010. It worked OK in the ON (Canada)>AZ (USA) trip in January 2011, and the return AZ>ON trip in early April.

But it didn't work so well in the ON>AZ in January 2012. Had to stop a couple of times in the high altitude Organ Mountains in NM East of Las Cruces as trans temps were in the 225F range. I have a Scanguage II.

In the return trip from AZ>ON in April 2012, it was terrible from Tucson to Tulsa. Day temperatures were above normal for the time of year, i.e. about 90F degrees with a very hilly up and down road in high altitudes. Had to stop a number of times, or drive at 45mph on the Interstate for the tranny to stay cool. Sometimes we couldn't drive at all in the afternoon, it was too hot. Driving conditions were bad until we reached cooler climes near Tulsa.

We were pulling our travel trailer RV: GVWR 3150lbs, flat curved front, about 10.5' high, 8' wide (head winds also cause tranny temps to rise). See attachment.

Obviously there is not enough air getting to the cooler due to the obstruction of the "badge" across the front of the radiator, or the cooler is not big enough, or the Trailblazer is not powerful enough. The Tru-cool is installed on the passenger side of the radiator and uses almost all the available area. I'm now wondering what to do in preparation for next years trip. Suggestions will be welcomed.

NB the vehicle is absolutely ok with no trailer, i.e. the tranny temps stay down and there's lots of power and acceleration.

Trailblazer, I6, 2007, 72K miles.

 

[The_Roadie]

Were you towing in 2nd or 3rd? How many miles on the truck? Miles since last transmission service?

I have a 3000 pound Trailmanor (hard-sided pop-up basically) and I'm down to 2nd on a lot of hot uphills, and don't get worried with short-term trans temps of 225-230.Just don't do it for a half hour at a time.

Just confirming you have the stacked plate design, not the cheapie tube & fin?

Checked behind the cooler for airflow-robbing debris?

 

[mark'stb]

Any debris in the fins? I'd remove the cooler and blow air through it from the rad side towards the front side of the cooler.

Whoops..didn't see the roadies last line. Got taken back by Sheldon.

 

[The_Roadie]

Bazinga!

 

[RedEnvoyDenali]

The Tru-Cools are all a stacked plate design as far as I know. Your cooler is good for 18000 lbs gross which should be enough to work with your load. The Tru-Cool 4589 which is about the same size and fits in our trucks quite nicely is 1 1/2" thick and has a rated capacity of 21000 lbs. Not sure if the larger one would cure your problems but it does have almost 20% more capacity and fits.

If the cooler is mounted in front of the Rad it should get lots of air unless there is blockage by some foreign material.

As you can see from the chart you should try to keep temps around the 200 degree mark for long tranny life.

Transmission temperature/failure chart.

Let us know what you decide to do.

 

[truck2trail]

Were you towing in 2nd or 3rd? I always keep it in 3rd when towing, and let it automatically go to 2nd, or kick the accelerator to make it go down. Are you saying I should move the shift handle to 2nd on hills ? I would have thought this would have made the tranny temp hotter with the extra revs ?

How many miles on the truck? Miles since last transmission service? 72K and 7K. Always get truck checked over at dealer in ON before we leave for AZ.

I have .....trans temps of 225-230. Just don't do it for a half hour at a time. OK, but note there is a lot of difference between a pop-up and my unit re air pressure on the front 88 sq. feet.

Just confirming you have the stacked plate design, not the cheapie tube & fin? Good question. I'm attaching some photos - you tell me please ! Didn't know much about these coolers when I got it installed, and didn't get details from AMCO at the time.

Checked behind the cooler for airflow-robbing debris?

No.... will do. I blew into the cooler TOWARDS the rad with water hose. I appreciate that is not as good as doing it from behind, but I don't think that is going to make a real difference ?

 

[truck2trail]

Just bringing this topic to the top again as there's been no more replies since last week.

My own preference is to remove the Badge and the plastic bar that goes across the radiator and see if it makes a difference. In my opinion this bar blocks a lot of the surface area of the Tru-cool. I think removing this stuff is quite easy and I could do it for the trip down to AZ and the trip back (the more susceptible time to problems) to ON. I'd replace the bar when I wasn't doing any towing. What do you think ?

 

[RedEnvoyDenali]

Just bringing this topic to the top again as there's been no more replies since last week.

My own preference is to remove the Badge and the plastic bar that goes across the radiator and see if it makes a difference. In my opinion this bar blocks a lot of the surface area of the Tru-cool. I think removing this stuff is quite easy and I could do it for the trip down to AZ and the trip back (the more susceptible time to problems) to ON. I'd replace the bar when I wasn't doing any towing. What do you think ?

I don't think you are going to see any difference taking anything off the front of the vehicle. You may need a cooler with more capacity. The front of the trailer is like a large sail so when you get up high (thinner air) on a hot day, and making the TB work even harder, that would be a recipe for overheating. Do you have any trouble with the radiator getting hot. If not it is getting the same air as the tranny cooler. The only difference is that tranny's make a lot of heat very quickly when put to work. I would try a larger cooler or even perhaps another one in series with the one you have now.

I think you said you have it on the passenger side. I have mine on the drivers side so there is room for one there as well. If you go with the double unit you might get it plumbed so that you can bypass it in the winter (although Tru-cool have a cold oil bypass built in). I tow a 4000 lb boat however it doesn't have a sail and is fairly aerodynamic, but never a problem with tranny heat.

Good Luck I hope you get your problem solved because tanny's are expensive.

 

[Wooluf1952]

Has anyone looked into the coolers that have a separate fan, dedicated strictly for the cooler?
I haven't seen any that are the stacked plate type.
They can be remote mounted, so they don't interfere with the air flow thru the radiator or AC.

 

[AtlWrk]

Has anyone looked into the coolers that have a separate fan, dedicated strictly for the cooler?
I haven't seen any that are the stacked plate type.
They can be remote mounted, so they don't interfere with the air flow thru the radiator or AC.

JEGS Performance Products 60346 JEGS HP Transmission Coolers

 

[Bartonmd]

Wait... You're scared and pulled over for the 225F range?? That's what the I6 TBs run, stock, empty, for 100k+ miles. 240-250F is still fine, for short periods.

Having said that, the I6 TC does make a TON of heat when it's unlocked.

Also, Kyle was having temp issues, and sprayed his stacked plate cooler from the rear, and a whole bunch of bugs and stuff cam out of it. Temp issue pretty much went away.

Mike

 

[strat81]

Do pans like this work, or are they bunk? TCI 378000 TCI Cast Aluminum Deep Transmission Pans

And by "work", I mean do they help lower fluid temps?

 

[Bartonmd]

Yeah, they do help. How much, I don't know.

Mike

 

[Mooseman]

We already have a deep pan and even if it did add some extra fluid capacity, all that would do is take a little longer for all the fluid to get hot during a long hard pull. The temp chart does say failure at "average" temperatures. So if it runs mostly in the 200f range or lower, then your average should be pretty good. To improve on it, I would go like this:

1. Change the filter and fluid to DexVI unless it's already been done recently
2. Check tranny line routing if it's passing near or touching exhaust components
3. Pressure wash tranny cooler and radiator (carefully with the high pressure against the radiator fins as it could damage them)
4. Ensure cooler is connected properly. It should be connected to the radiator cooler's outlet (IIRC is on the driver's side). The fluid should flow from the tranny to the radiator cooler, then out from radiator cooler to the auxiliary cooler, then out to tranny return line. If connected the other way around, the hot radiator could add heat to the fluid.
5. Ensure that your fan is working correctly ( I can't tell which year you have since it's missing from your profile. This would tell me if you have the problem prone electro-viscous fan clutch or the newer (and simpler) viscous clutch).

If all this doesn't help, you could add a small electric fan if there is room in front of it.

 

[dougman]

I bought this fan Amazon.com: PROCOMP 7" INCH ELECTRIC AUTO COOLING FAN 12 VOLT CURVED BLADE: Automotive to put on my Hayden cooler (looks very much like yours). Just barely fits in every dimension - height, width, and depth. Moves a respectable amount of air. I added a Hayden adjustable mechanical control to it. It has a sensor bulb which I strapped to the outlet side of the transmission. I have it set to come on around 190, so mine never turns off. However, as shown by the lifetime charts, as long as it's not too cold, in my opinion the colder the better. If you do buy that fan, remember it is setup as a puller. You need to reverse the polarity of the input and remove and flip the fan assembly. Really unbeatable for the cost. I'm sure you could do better with one of those nice $180 coolers with fans attached, but this at $30.00 shipped is a bargain. Good luck!

 

[truck2trail]

......... I would try a larger cooler or even perhaps another one in series with the one you have now.........

Yes, I think this is the way I'll go, i.e. put a 2" thick cooler (maybe overkill - but so what !) in series on the driver's side. If this doesn't work, then the days of the Trailblazer are definitely numbered !!

 

[RedEnvoyDenali]

Yes, I think this is the way I'll go, i.e. put a 2" thick cooler (maybe overkill - but so what !) in series on the driver's side. If this doesn't work, then the days of the Trailblazer are definitely numbered !!

Not sure I have seen any 2" thick coolers but Tru-Cool does have a good selection of 1 1/2" ones. What one did you decide on? I am not sure you can "Overkill". Good Luck.

 

[truck2trail]

Not sure I have seen any 2" thick coolers but Tru-Cool does have a good selection of 1 1/2" ones. What one did you decide on? I am not sure you can "Overkill". Good Luck.

So finally, last week i took off the radiator grill and determined the cooler already installed (A) on the passenger side was a Tru-cool LPD4454. So I ordered another one (B) that I will install on the driver's side.

For the following, imagine you are in front of the vehicle looking at the grill, i.e. the driver will be on your RHS.

From the installation instructions, it appears it doesn't matter how I connect up (A) and (B), i.e I can just cut the hose going to the RHS in/outlet of (A), and then connect a separate short piece of hose from the RHS in/outlet of (A) over to the LHS in/outlet of (B). Then a short piece of hose from the RHS in/outlet of (B) over to a connector to the previously cut piece of hose (that previously went to the RHS of (A)). Use hose clamps where needed. Can you please confirm you agree with this ?

What kind of connector should I use ? Metal I presume with hose barb 11/32" at each end ? (Home Depot ?)

How can I determine the previous installation of (A) was done correctly without disconnecting anything ? i.e. the (A) cooler is placed so the fluid enters the cooler AFTER it has firstly gone through the bottom of the radiator ? e.g. are the tubes connected to the rear/front of the transmission casing so the hot line is at the front/back ?

Thanks

 

[RayVoy]

Adding a second trans cooler to the left of the one already in place might help the tranny heat problem, but I might block too much air from the radiator and cause the engine to overheat.

I think, if I though I needed more cooling, I'd increase the size of the first one.

How can I determine the previous installation of (A) was done correctly without disconnecting anything ? i.e. the (A) cooler is placed so the fluid enters the cooler AFTER it has firstly gone through the bottom of the radiator ? e.g. are the tubes connected to the rear/front of the transmission casing so the hot line is at the front/back ?

Thanks

The best way to find the out (hot) line and the in (cold) line is to use a temp gauge (maybe a thermometer) if you have one, the other not so reliable way is to feel the lines with the fingers (careful, hot) to see which is hotter.

 

[truck2trail]

Adding a second trans cooler to the left of the one already in place might help the tranny heat problem, but I might block too much air from the radiator and cause the engine to overheat.

I think, if I though I needed more cooling, I'd increase the size of the first one.


The best way to find the out (hot) line and the in (cold) line is to use a temp gauge (maybe a thermometer) if you have one, the other not so reliable way is to feel the lines with the fingers (careful, hot) to see which is hotter.

Bit late to tell me that now !!! I guess I'm going ahead with the double and we'll see ! The current one installed is the LPD 4454 (7.25X11X0.75) at 18,000 GVW. The next size up (LPD 4490, 12X11X3/4) at 22,000 GVW (not sufficient of an increase ?) is too long, much of it would be below the bumper. The other option would be the LPD4589 (8X11X1.5) at 24,000 GVW (not sufficient of an increase ?). I'm not sure if that thickness would fit. With two LPD 4454's I should get 36,000 GVW. I'm obviously between the devil and the deep blue sea !

Thanks for the tip re hot & cold lines.

 

[RayVoy]

Bit late to tell me that now .

Yeah, I know, and that's just my opinion, it may work fine and solve all of the heat problems.

Here is an other opinion that I have.
The standard way to connect the cooler, is to set it in series with the return line from the radiator to the transmission, this means, that the hot (hotter than it should be) fluid is going into the radiator first, getting some cooling and then hitting the tranny cooler, finally returning to the transmission.
This means, that the extra hot tranny fluid is adding to the cooling load of the radiator.

I think, if the fluid went to the cooler first, a lot of the heat would be pulled out of it before it entered the radiator, the radiator could remove even more (but at less load to the cooling capacity), the fluid would return to the tranny at, or a little below the temp of the engine coolant.

I know, the thought is that if connected in the "standard" way, during engine warm up, the tranny heat is pulled into the engine coolant thus warming the engine faster; however, this can be accomplished with a cooler bypass.

An engine oil cooler is an additional option, it also can be installed in front of the radiator.

 

[truck2trail]

I think, if the fluid went to the cooler first, a lot of the heat would be pulled out of it before it entered the radiator, the radiator could remove even more (but at less load to the cooling capacity), the fluid would return to the tranny at, or a little below the temp of the engine coolant.

An engine oil cooler is an additional option, it also can be installed in front of the radiator.

OK. Thanks for the thoughts. I'll do it the "standard" way first, but if the engine temp goes up to much, I'll try the above ideas. Or sell the vehicle !

 

[Indybp57]

I installed a Trucool 4589 on my Trailblazer a few months ago. I also tow a TT but don't have a scanner to monitor the temperature. IMHO, removing the badge, braces, etc is not going to make a significant difference, you're just splitting hairs, besides the badge and brace are in the middle, the cooler is off to the side. I believe the prescribed routing from Trucool is to put the cooler in the return line back to the tranny. My TT is a slightly heavier than yours, and it is quite a load for that vehicle, especially in hilly terrain. I got a PCM tune that helped greatly on the hills, it is not nearly as apt to downshift all the way to first everytime I give it some gas on a hill. In the stock PCM configuration the engine was screaming in first about half the time. I tow with the selector in 3rd to eliminate some of the downshifting and associated transmission heat buildup. Having said all that, you may find you just need a better tow vehicle for the type of towing you do.

 

[truck2trail]

I installed a Trucool 4589 . I got a PCM tune that helped greatly on the hills.

Interesting. Thanks.

Q1: Did you find the 4589 fitted OK ? Any mods needed ? Driver or passenger side ?

Q2: PCM tunes are new territory to me. Don't know anything about them. I'll do some research. In the meantime, where did you get yours from, which model, and where do they fit into the vehicle ?

Thanks again.

 

[Indybp57]

Interesting. Thanks.

Q1: Did you find the 4589 fitted OK ? Any mods needed ? Driver or passenger side ?

Q2: PCM tunes are new territory to me. Don't know anything about them. I'll do some research. In the meantime, where did you get yours from, which model, and where do they fit into the vehicle ?

Thanks again.

A1. Driver's side but don't think it really matters. The outside temp sensor is right behind it and therefore it always says it is 130+ degrees outside. I did have to trim the plastic around the hood latch assembly a little and will eventually relocate the temp sensor. The cooler occupies the entire space tonthe right of the center brace.

A2. PCMforless.com. I pulled my PCM and sent it to them for reprogramming but they have other options. You will find lots of threads on this forum and on the old trailvoy site on this subject. The pcm is mounted on the drivers side of the engine.

 

[Mooseman]

A1. Driver's side but don't think it really matters. The outside temp sensor is right behind it and therefore it always says it is 130+ degrees outside.

This is an easy fix. Just pull the sensor out and move it to a new location in front of the cooler. Either drill a new hole in a new location or zip tie it to the center brace or hood latch cable.

 

[Irishboy02]

Im going to reply on the gear selection that was talked about earlier. Keep the shifter on 3 for your whole trip. If you start bogging going up a hill then you can kick it down to two, but back up to third once you get over. Never pull this load in D, youl be banging in and out of overdrive and RPMs wont get high enough to keep proper cooling. Having the lower gear selected will allow your RPMs to rise. This will not only increase your torque and help you get over, but since engine speed is increasing and you have a mechanical fan, it will also allow the fan to spin faster allowing more air to flow through and help with cooling. Especially since you are up in the mountains where the air is already thin.

 

[Mooseman]

Another thing is that by having it in third, it will allow the torque converter clutch to engage more often and longer. If you're in OD, the TCC will not be able to engage and the torque converter will generate heat continuously churning the fluid. And the constant shifting from OD to 3 will also generate heat from the clutch pack friction. There is no fuel savings while towing anyway so using OD is pointless.

 

[truck2trail]

Thanks for responses. No problem, I ALWAYS drive in 3rd when I'm pulling the trailer.

So, I have received my additional cooler, LPD4454, but I thought I would do some temperature checks on current installation (one Trucooler) before I started.

So, NOW, I am concerned as follows:

With the TB warmed up and driven for 4 miles (no trailer), and sitting in the driveway with the engine running, i.e. the vehicle is stationery, but the fan is whirling, and with a temperature of 145 degrees on the Scanguage II of 145 degrees F, the temperatures were as follows: (all being recorded near the radiator)

Metal Pipeline (A) from transmission into bottom of radiator = 111 degrees F,

Metal Pipeline (B) from bottom of radiator into hose into Trucooler = 101 degrees F

Metal Pipeline (C) going to transmission, connected from Trucooler hose = 107 degrees F

From this I conclude the temperature has dropped 10 degrees F across the bottom of the radiator, but has increased by 6 degrees F going across the Trucooler, giving a difference in temperature of 111-107 = 4 degrees F from and to the transmission.

Can anyone make sense of this ? Thanks

 

[The_Roadie]

What are you measuring the temps with, and what's its accuracy?

145 isn't even opening the thermostat. Recommend running it at full temp up a few hills, then repeat the measurements.

 

[truck2trail]

What are you measuring the temps with, and what's its accuracy?

145 isn't even opening the thermostat. Recommend running it at full temp up a few hills, then repeat the measurements.

An oven meat thermometer - pretty accurate IMHO ! Electronic.

145 was the temperature of the Tran Fluid (TF) . The engine was at it's usual 100 degrees (as measured on the gauge in the instrument cluster).

Are you talking about the Trucooler thermostat ? At what temperature does this thermostat open ?

Will re-run if I can find any real hills around here !

Thanks.

 

[The_Roadie]

Sorry, I forgot you were in CA.

The instrument cluster gauge lies. You need a scan tool to be looking at the real data stream, before the filtering and lying that the PCM presents to the instrument cluster.

There is no thermostat in the cooler like there is in the angine coolant flow.

145 C is 293 F, and the tranny should NEVER be allowed to get that hot. I bet that's 145F. I think you need to be looking at the true data stream using the vehicle's own sensors. An oven meat thermometer may be PRECISE, but in my experience it's not ACCURATE. The display is not a good reflection of its accuracy as a scientific instrument.

At the very least you should be using a non-contact infrared gun sort of sensor, if not a real thermocouple instrument.

 

[RayVoy]

and with a temperature of 145 degrees on the Scanguage II of 145 degrees F, the temperatures were as follows: (all being recorded near the radiator)

Metal Pipeline (A) from transmission into bottom of radiator = 111 degrees F,

Metal Pipeline (B) from bottom of radiator into hose into Trucooler = 101 degrees F

Metal Pipeline (C) going to transmission, connected from Trucooler hose = 107 degrees F

145 isn't even opening the thermostat.

145 was the temperature of the Tran Fluid (TF) . The engine was at it's usual 100 degrees (as measured on the gauge in the instrument cluster).

Sorry, I forgot you were in CA.



145 C is 293 F, and the tranny should NEVER be allowed to get that hot. I bet that's 145F.

We have a huge amount of confusion here, the OP provided some temps in F (those read with the oven temp display, and offered the dash water temp in C.

AFTER ONLY 4 MILES, the dash gauge may read 100c, but the truck is not at normal operating temps.

As roadie suggested, it needs to be driven for a longer period of time.

And roadie, I suspect the OP is using a handheld IR thermometer, I have one, and it appears to be both sensitive and accurate.

 

[Bartonmd]

They're sensitive, but they're only accurate based on the reflectivity of the particular surface. Different metals, different paints, different other materials, etc. can all be the same temperature, but the IR temp gun will read it differently. The decent ones have different settings for different materials and finishes.

Mike

 

[truck2trail]

Please find new temperature readings after an one hour drive. ALL the temperatures in the text and the numbers in the diagram are in Farenheit. My apologizes about the confusion in the previous posting.

According to my Scanguage II, the TFT was at 203, the water in the radiator was at 207, the IA temperature was 110, and the outside air temperature was 72.

Re the accuracy of the temperature recorder, it seems to me the relative readings are more important than the actual accuracy of the absolute readings.

Regarding the attached diagram, which shows the plumbing connections, the temperatures recorded only make sense to me if the transmission cooling fluid is circulating in a CLOCKWISE direction. That is, the fluid leaves the transmission at T1 at 141 degrees, and then flows through the Tru-Cooler which reduces it to 125 degrees. The fluid ENTERS the radiator via the connection on the driver’s side (contrary to normal practice), and is heated UP to 143 degrees. This seems logical since the radiator temperature is at 207 degrees. The fluid then enters the transmission at T2 at a temperature of 143, i.e. apparently HOTTER than when it left !

The fluid circulating in an anti-clockwise direction, i.e. leaving T2 at 143, being cooled down to 125 as it passes through the radiator (at 207 degrees ?!!), then HEATED UP to 141 as it passes through the Tru-Coller, makes no sense to me.

When I bought the vehicle, the DODGE dealer installed new pipes. Could the mechanic have mistakenly criss-crossed the pipes and transmission connections ?

Any suggestions as to the quickest way to correct the above situation ? (Chevy dealer to re-do connections at transmission ?)

Thanks

 

[Mooseman]

T2 is the outlet from the tranny. The schematic is showing the proper way to connect the cooler. You want the fluid going through the radiator first because if you cool it more than what the radiator temperature is, you would be putting heat back into the fluid. You would get a bit of cooling with the rad cooler first then a lot more cooling from the aux cooler. All installation instructions I have seen say to hook it up this way.

 

[truck2trail]

T2 is the outlet from the tranny. The schematic is showing the proper way to connect the cooler. You want the fluid going through the radiator first because if you cool it more than what the radiator temperature is, you would be putting heat back into the fluid. You would get a bit of cooling with the rad cooler first then a lot more cooling from the aux cooler. All installation instructions I have seen say to hook it up this way.

You are right in principal, but unfortunately on my vehicle, they mistakenly switched the tubes at the top connection point near the passenger's side, just behind the radiator when the Dodge dealer replaced them, i.e. the tubes going to radiator are two tubes, each tube has two sections. A friend and I looked at this point this afternoon, and it's obvious that's what happened, hence giving me the incorrect flow, i.e. the fluid is going through the Tru-Cool BEFORE it gets to the radiator !!

I'm taking it to the dealer next week. Should be a quick and inexpensive fix. Thanks for your reply.

 

[Mooseman]

Are you sure that they did that? You should disconnect one of the lines entering the radiator and see where fluid flows out from. Have someone just give it a quick crank and it will be quickly evident which way the fluid flows.

 

[truck2trail]

Are you sure that they did that? You should disconnect one of the lines entering the radiator and see where fluid flows out from. Have someone just give it a quick crank and it will be quickly evident which way the fluid flows.

As soon as I disconnect either of the Tru-cooler hoses connected to the radiator, won't fluid gush out from the Tru-cooler ? The connections from the Tru-cooler to the radiator are at the bottom of the radiator and the Tru-cooler is near the top of the radiator. Even assuming I let it gush out until the Tru-cooler is empty, if it's going to the Tru-cooler first, which I think it is, it'll be a long waiting time before any comes out after the draining. And then the return, which I believe is going to the radiator, will have no fluid going to the transmission for that waiting time. Is that safe ?

If you look at my diagram, in the current set-up, you'll see that the fluid must be going to the Tru-cooler first, as the entry temperature is 141F and the exit temperature is 125F, i.e. the fluid has been cooled down by the Tru-cooler, which is logical. If it's coming to the Tru-cooler last then the Tru-cooler is HEATING IT UP from 125F to 141F !! Which I submit is not logical.

Another reason I'm sure the dealer didn't make the right connections at the top of the radiator, is that only one tube is in the clip holder, the other is hanging loose.

 

[NJTB]

Yes, it will leak fluid. Just catch it in a pan. Re-route the hoses the way you want, and get a couple of quarts of trans fluid. Start the car and let it idle, then add the trans fluid until it's just below the grid on the dip stick. Drive it around until it's at operating temp, then fill the trans to 'full'. The fluid will expand, you may not need to put any more in. Drive it easy, you'll do no damage.