New engine running hot!

Gordo

Original poster
Member
Mar 26, 2012
81
I got the "new" engine in and running. It is from a wreck with 77,000m. I find that it will idle for an hour with no overheating issues but once I start driving it, the temp starts to climb 15 minutes into the run. When this happens, I cannot hear the fan, in fact I only hear that whine when I first start it cold. I had to pull over yesterday to stop it from boiling. I waited 10 minutes and on startup, the fan did not engage. Can anyone tell me which sensor turns this on and off? I don't want to start changeing parts unless I know where I should be going. My scrap motor is in the shop so I have an extra water pump, thermostat ECM and what ever I may need. With the motor idling and the temp at 212 (from my scan tool), the fan is not engaged. I unplugged the connector and no change, but this did give me a code that the fan had lost signal. Thanks!
 

n0kfb

Member
Dec 8, 2011
104
Why did you replace the engine? Did you replace the thermostat? Did you purge the air in the cooling system?

I'm sure others will come up with more tips and questions.

-- Dan Meyer :coffee:
 

n0kfb

Member
Dec 8, 2011
104
limequat said:
I say jump the clutch with 12V and see if it engages at temp.

I would not recomend this without investigating how the fan clutch works, or at least checking what it says in a service manual first. It is my understanding that the fan clutch never gets a full 12 volts applied directly, it only gets pulsed 12 volts. If it is not designed to get constant 12 volts, testing in this fashion may burn it out.

Second, if you are moving at speeds over 30 MPH or so a fan is not needed. If your truck is overheating at speed, it isn't a fan clutch problem.

-- Dan Meyer :coffee:
 

ScarabEpic22

Member
Nov 20, 2011
728
Sounds like you need to burp the coolant again, try that first then report back.
 

Gordo

Original poster
Member
Mar 26, 2012
81
ScarabEpic22 said:
Sounds like you need to burp the coolant again, try that first then report back.

I have not been able to find a "procedure" for this engine. If there is one, I would like to know what it is!
 

Gordo

Original poster
Member
Mar 26, 2012
81
n0kfb said:
Why did you replace the engine? Did you replace the thermostat? Did you purge the air in the cooling system?

I'm sure others will come up with more tips and questions.

-- Dan Meyer :coffee:

Hi Dan, replacing the engine is a long story, short version is, it was cheaper to drop in a complete motor than fix what I had. The used motor is low mileage and no I did not change the T stat. I filled the coolant system and brought it to temp with the rad cap off, heater on. Installed the cap, filled the overflow resevoir and all was good till I drove it for 20 minutes. It escalated from normal to hot in about 5 minutes. As hot as it was, the fan clutch did not sem to be engaging. Seems to me the fan should lock up when needed, ie, when the temp exeeds a threshold. This "circuit" does not seem to be working.
 

n0kfb

Member
Dec 8, 2011
104
Gordo said:
I have not been able to find a "procedure" for this engine. If there is one, I would like to know what it is!

Have you spent any time reading the documentation? If nothing else, head to your local public library and read the service manuals they have there. You might also check something called 'Alldata' that they should have available for free. If you would like to stay at home, alldata is available by subscription for a nominal fee - see ALLDATAdiy.com Leading Source of Factory Automotive Repair Information for details.

-- Dan Meyer :steer:
 

jimmyjam

Member
Nov 18, 2011
1,634
n0kfb said:
Second, if you are moving at speeds over 30 MPH or so a fan is not needed. If your truck is overheating at speed, it isn't a fan clutch problem.

:iagree: if its overheating while driving on the highway, you've either got a tstat stuck closed, air in the head, or blockage
 

Mooseman

Moderator
Dec 4, 2011
25,580
Ottawa, ON
I don't think there would be a problem temporarily jumping the fan supply wire (white). I remember a thread on the OS where someone ran an override switch to that wire because he wanted to be able to run the fan at 100% when he was towing. The PCM would command the fan to 100% if there was the need, which might be near overheat condition I would imagine.

For your particular problem, check/replace the following in this order:


1. Clean the radiator fins as well as the A/C condenser for debris
2. if overheating while idling or slow moving, check operation of fan, replace if necessary
3. replace thermostat and temp sensor just above it
4. use a 50/50 mix of Dexcool coolant/water for better heat transfer.
5. Have the radiator cleaned inside for blockage

If you need manuals, check the link in my sig.
 
Feb 24, 2012
133
I will 2nd the idea of an air pocket needing to be bled. Also sounds like your fan clutch isn't engaging. Can you take the fan clutch off your old engine?

edit: 212? I don't think that's hot enough to engage the fan clutch. Does anyone with a service manual or tuner know? Also, how hot is "overheating"? 212 is not close to boiling.
 

Gordo

Original poster
Member
Mar 26, 2012
81
deekster_caddy said:
I will 2nd the idea of an air pocket needing to be bled. Also sounds like your fan clutch isn't engaging. Can you take the fan clutch off your old engine?

edit: 212? I don't think that's hot enough to engage the fan clutch. Does anyone with a service manual or tuner know? Also, how hot is "overheating"? 212 is not close to boiling.

The more I read about this, the more I think the fan clutch is the culprit. I do not have a spare so would like to diagnose it first. All I read is it should be harder to turn by hand when the motor is hot. This does not seem to be what is happening. I am going to change the thermostat and temp sender tonight, as I have those parts from my old motor and retry it. The clutch is not cheap so would like to confirm that's the problem before I spend any more money. If I put 12v to it, it should lock up? Can anyone confirm this?

Thanks!
 
Feb 24, 2012
133
Gordo said:
All I read is it should be harder to turn by hand when the motor is hot. This does not seem to be what is happening.

This fan clutch is electrically engaged. There is no thermostat in the fan clutch. It will only be hard to turn if voltage is being applied from the PCM. It has nothing to do with the temperature of the coolant, besides what the PCM thinks the coolant temp is. It's an electrical actuation, not by a mechanical thermostat as all other fan clutches are.

But at cruise, you should NOT need the fan. I ran with the fan removed from my 8.1 until just a couple weeks ago when it started getting hot out, I wanted to use the A/C while sitting in traffic. I have had NO fan on my truck since december.

What is "hot"?
 

Gordo

Original poster
Member
Mar 26, 2012
81
deekster_caddy said:
This fan clutch is electrically engaged. There is no thermostat in the fan clutch. It will only be hard to turn if voltage is being applied from the PCM. It has nothing to do with the temperature of the coolant, besides what the PCM thinks the coolant temp is. It's an electrical actuation, not by a mechanical thermostat as all other fan clutches are.

But at cruise, you should NOT need the fan. I ran with the fan removed from my 8.1 until just a couple weeks ago when it started getting hot out, I wanted to use the A/C while sitting in traffic. I have had NO fan on my truck since december.

What is "hot"?

My Haynes manual specifically says "Drive the vehicle till the engine is warmed up. Shut it off and remove the key. Turn the fan blades again and note the resistance. There should be a noticeable increase in resistance. If the fan clutch fails this check or is locked up solid, replacement is indicated." This section starts off by that this is an electro-viscous PCM controlled unit.

What is hot? It will hit the red zone if I don't shut it down.
 
Feb 24, 2012
133
I would start with the thermostat. But you may have an issue with the fan clutch as well.

Sorry I can't confirm about the solid 12v question.
 

Denali n DOO

Member
May 22, 2012
5,596
I was reading a thread yesterday, I think it was called " I just got a new tent trailer" or something like that. There was a post in there that referenced putting a switch in for the fan so it could be turned on whenever he wanted. I can't find that thread now, I didn't see it in the towing section. He may be able to answer your question about 12v to the fan.
 

Pittdawg

Member
Dec 5, 2011
538
limequat said:
OP, if you don't want to deal with the EV fan, the 2008 trailblazers have a good ol' fashioned mechanical clutch.

Yes they do. Buy mine so I can upgrade to an efan :cool:
 

Mooseman

Moderator
Dec 4, 2011
25,580
Ottawa, ON
He can't use a 2008 clutch unless he gets the fan error codes turned off. For the replacement of the thermostat and sensor, why bother with used ones? With the trouble of replacing them, might as well go with new.
 

Gordo

Original poster
Member
Mar 26, 2012
81
Changed Tstat, temp sensor and coolant. I am getting the same problem, idles fine @ 100c but 5 minutes down the road, the temp rises fast. Whats left, water pump and rad? The rad sat for several months, the water pump was on the used motor.
 

Mooseman

Moderator
Dec 4, 2011
25,580
Ottawa, ON
Water pumps don't stop pumping when they fail unless the impeller separated from the shaft, which is rare. They usually just leak or have bad bearings. If it was the pump, then even at idle it would overheat real fast. If it's heating up at speed, I'm thinking the radiator has internal blockage. Maybe take the radiator to a rad shop to have it cleaned out.

Have you tried pressure washing the exterior of the radiator and condenser?
 

n0kfb

Member
Dec 8, 2011
104
Gordo said:
Changed Tstat, temp sensor and coolant. I am getting the same problem, idles fine @ 100c but 5 minutes down the road, the temp rises fast. Whats left, water pump and rad? The rad sat for several months, the water pump was on the used motor.

Is your check engine light on? Read the codes! The temperature gauge doesn't actually read temperature, but the computer moves the needle to get your attention.

If there are no codes, do the following: Pressure test the cooling system including the radiator cap. Check the lower radiator hose. If you can squeeze it on a cold engine it may be collapsing at higher RPM's. Also clean the outside of the radiator and A/C condensor.

-- Dan Meyer :coffee:
 

Gordo

Original poster
Member
Mar 26, 2012
81
n0kfb said:
Is your check engine light on? Read the codes! The temperature gauge doesn't actually read temperature, but the computer moves the needle to get your attention.

If there are no codes, do the following: Pressure test the cooling system including the radiator cap. Check the lower radiator hose. If you can squeeze it on a cold engine it may be collapsing at higher RPM's. Also clean the outside of the radiator and A/C condensor.

-- Dan Meyer :coffee:

No codes but my scanner gives me a temperature readout. It seems accurate. I'll go at the rad tonight. I have a spare water pump so may change it anyway. Bottom rad hose is good, looking like the rad!
 

CaptainXL

Member
Dec 4, 2011
2,445
I have read many articles that state its good insurance to put in a new t-stat and coolant temp sensor when replacing an engine.
 

CaptainXL

Member
Dec 4, 2011
2,445
Mooseman said:
Maybe take the radiator to a rad shop to have it cleaned out.

It would more than likely cost you about as much to buy a new radiator. Its common practice only on big rigs.
 
Feb 24, 2012
133
If you idle it for a long time it doesn't get hot, right? Just to normal temp? Then if you drive it a few minutes it gets hot - if you Park and let it idle does it cool back down, or does it get hotter?
 

Gordo

Original poster
Member
Mar 26, 2012
81
I think I have it solved. Installed a NEW rad and while I was in there, I pulled the water pump. It had quite a lot of rust on it, especially on the input end where it needs a really good fit against the block to pull vacuum and make it pump. May have been cavitating here. Also, there is a slot in the block above the pump. This can be seen with a mirror and a flashlight. Mine was plugged with a pasty substance that I had to dig out with a pick. Not sure if this is relevant or not but my old block was spotless in this area. Put the used pump in as it looked perfect, installed new rad and test drove. Worked perfect for most of a one hour cruise. The temp rose just above 100c about 3 notches for a few minutes and then returned to normal and stayed there. I'll try it again when my new rearend pot cover comes in tomorrow. It rusted through and there wasn't a dealer in 500 miles that had stock! Why does NAPA have these covers in stock for the Silverado and not even a listing for the Envoy?? Had to dealer order it.
 

Mooseman

Moderator
Dec 4, 2011
25,580
Ottawa, ON
Probably went high for a little bit until the thermostat opened and "burped" the system of air. Sounds like the wrong coolant was used or poorly maintained in the past, causing blockage. The blockage of the passage in the block itself supports that theory. Mixing green coolant and Dexcool will cause gelling and possibly other nasty stuff.

Did you look up the GM parts numbers for both? I looked it up at RockAuto and GENERAL MOTORS Part # GM26067595 fits our trucks as well as the Silverado. It is the most common cover for just about everything since the mid-60's with the 8.5" diff.
 

Gordo

Original poster
Member
Mar 26, 2012
81
Mooseman said:
Probably went high for a little bit until the thermostat opened and "burped" the system of air. Sounds like the wrong coolant was used or poorly maintained in the past, causing blockage. The blockage of the passage in the block itself supports that theory. Mixing green coolant and Dexcool will cause gelling and possibly other nasty stuff.


Did you look up the GM parts numbers for both? I looked it up at RockAuto and GENERAL MOTORS Part # GM26067595 fits our trucks as well as the Silverado. It is the most common cover for just about everything since the mid-60's with the 8.5" diff.

Can't comment on the previous coolant as this is a used engine I do not know the history on. All I know is the mileage (77K miles) and that it came out of a US wreck. I hope it was just air, I've changed everything but the fan!


I did not look up the numbers myself, I called NAPA nad was told they did not have a part #. When I went to the stealership, the parts dude said they were in fact different. Peculiar to the TB, Buick and Olds versions of my Envoy EXCLUSIVELY! I would like to see them sisde by side, but it does not matter anymore as the new cover will be in tomorrow, new gasket and bolt kit. About $50, I'm OK with that.
 

Gordo

Original poster
Member
Mar 26, 2012
81
Gordo said:
Can't comment on the previous coolant as this is a used engine I do not know the history on. All I know is the mileage (77K miles) and that it came out of a US wreck. I hope it was just air, I've changed everything but the fan!


I did not look up the numbers myself, I called NAPA nad was told they did not have a part #. When I went to the stealership, the parts dude said they were in fact different. Peculiar to the TB, Buick and Olds versions of my Envoy EXCLUSIVELY! I would like to see them sisde by side, but it does not matter anymore as the new cover will be in tomorrow, new gasket and bolt kit. About $50, I'm OK with that.

Got the cover kit, part # 12479377. Google that # and up comes the Envoy. Not sure what the difference is.
 

Mooseman

Moderator
Dec 4, 2011
25,580
Ottawa, ON
Could be a notch for a bracket or the magnet is included (was it?). Who knows. The chrome cover from my old '78 Z28 would probably fit. Gotta be a reason why RA listed another cover that fits so many vehicles. Ok, enough with this :hijack:

Glad it seems you got your overheating issues resolved.
 

Gordo

Original poster
Member
Mar 26, 2012
81
Not sure if it was the waterpump , rad or a combination but it seems to be behaving itself! Thanks for all the input!:smile:
 

Mooseman

Moderator
Dec 4, 2011
25,580
Ottawa, ON
Glad you worked it out.
 

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