Overheating after repairs (See details inside)

[djthumper]

If I go to Advance Auto Parts, they can do that for me there, right?

The ones they use generally only read the code not go into reading the PIMs.

Yeah, but I haven't really gotten a clear answer as to that being the problem. Some say it would do it, other say it wouldn't.

With everything that you are saying and have one I would lean more to the exhaust system. But you need to be able to tell us more of what the temps are reading. Normal operating temperature is right at 210, If it goes above for a short period I would not worry so much about it. My ambient temp is around 115 and if mine is slightly higher when the RPMs go down I kind of expect it.

 

[NJTB]

OK, really stupid response.
Is the fan turning the correct way or maybe installed backwards? That will give you those symptoms.
With the steps you've taken, there's not much left. I'm assuming these were all NEW parts you installed?

 

[eXplicit]

I took it to have it tested. It turns out that there's combustion gas in the radiator. Probably needs a new head gasket. More work than I really wanted to do with it. Ugh, has anyone changed a head gasket? What's it like?

 

[Mooseman]

Not that easy of a job. Search for a very long thread by Octanerider. Didn't end too well. Lots of problems with broken head bolts which lead to having to yank the entire engine. Ended in failure due to a screw up by the machine shop.

 

[KNBlazer]

from past experience, this is what I would do... if you have a scanner like an Equus (sp) check your PCM calibration, take a picture of your screen or write them down...then go to this website and see if you're do for a PCM flash, when installing a new clutch (according to what the dealer told me 5 or 6 years ago) a new calibration must be installed... you will need your vin to see if you fall under this category... also your heating issues, try to replicate them with your AC off all the way home... my 04 TB EXT sucks in temps over 90 degrees with the AC On, temp always starts creeping up at stops when under these conditions... I ended up installing an electric secondary fan for these scenarios... it helps somewhat...

TIS

 

[KNBlazer]

..and if you are left nowhere, head on over to your dealer and cough up the $100 dollars for a diagnostic and see if they find anything....

 

[eXplicit]

The ones they use generally only read the code not go into reading the PIMs.


With everything that you are saying and have one I would lean more to the exhaust system. But you need to be able to tell us more of what the temps are reading. Normal operating temperature is right at 210, If it goes above for a short period I would not worry so much about it. My ambient temp is around 115 and if mine is slightly higher when the RPMs go down I kind of expect it.

It's not that it goes up and then drops down. It continues to rise if I'm sitting idle after coming off the interstate. When I start driving, it will hover around the temperature it raised to (it varies depending on how long I sit), and then starts to quickly drop down.

OK, really stupid response.
Is the fan turning the correct way or maybe installed backwards? That will give you those symptoms.
With the steps you've taken, there's not much left. I'm assuming these were all NEW parts you installed?

The fan is was installed properly, and is pulling air IN through the radiator, not trying to push it forward. All the parts I've installed are brand new, no re-manufactured.

Not that easy of a job. Search for a very long thread by Octanerider. Didn't end too well. Lots of problems with broken head bolts which lead to having to yank the entire engine. Ended in failure due to a screw up by the machine shop.

I started reading that thread, and got about 5 pages in, then started to cringe at the idea of having to do this myself. Wonder what it'd cost for a shop to do it.

..and if you are left nowhere, head on over to your dealer and cough up the $100 dollars for a diagnostic and see if they find anything....

Already determined over the weekend that there is exhaust gas getting into the cooling system. They said that it's more than likely a head gasket, but there's a small possibility it's a cracked head. Can't really determine until it's taken apart. I'm leaning towards a head gasket issue because if the head is cracked, I'm sure the cooling system would leak into the cylinder and cause smoke. There's no smoke coming from the exhaust which is making me think that it's only air being pushed into the cooling channel.

I was given a tip from the Goodyear Service Manager about using Sodium Silicate to fix the gasket without taking the engine apart. Has anyone had any good results with this? I'm not sure it's going to help me because the gas is being pushed INTO the cooling system, so I don't know how it would find the leak.

 

[The_Roadie]

Is the fan turning the correct way or maybe installed backwards?

You have to change the serpentine belt a lot to get it to go backwards, but that would also mess up the water pump impeller.

Fan blades have this property of mostly working (depending a bit on blade design) if they're put on backwards. You have to change the rotation to get them to blow instead of suck.

View attachment 29768

 

[NJTB]

You have to change the serpentine belt a lot to get it to go backwards, but that would also mess up the water pump impeller.

Fan blades have this property of mostly working (depending a bit on blade design) if they're put on backwards. You have to change the rotation to get them to blow instead of suck.

View attachment 16473

Yes, Roadie, I agree.
A LONG time ago, this happened to one of the guys working in the shop. After about a week of everyone scratching their head trying to help him, someone noticed a piece of paper blowing away from the radiator, put 2 and 2 together, and fixed it. The customer installed a water pump about a year before, and drove it like that (overheated at bout 40 mph, no overheating at idle) We were working piece work, and he lost a bunch of money on that job. I never forgot it, and for the steps the OP has taken, I thought it was time to think out of the box.
I'm not sure I'm buying the head gasket thing because when it's blown between the cylinders, there's bubbles in the overflow tank, and the coolant starts to get low. Since the coolant will leak into the cylinder when the engine cools a bit, there should be clouds of white smoke on the next start up.
I think I would let the car get cold, and then pressure check the system.

 

[Mooseman]

I think there are test kits that you can check yourself for exhaust gases called Block Tester. I can't believe that exhaust gases would cause overheating unless you lose coolant. If the radiator and tank are full and coolant is circulating normally, it should still cool. What about radiator blockage? You mention that as soon as you rev the engine, it cools down. I'm thinking something is impeding flow. Maybe a bad thermostat? Although rare, you might have gotten a dud.

Yeah, GM must have used self destructing head and exhaust manifold bolts or they don't think that someday they may need to be removed. They just seized right up in there. I sure hope this is not the case with your engine.

 

[eXplicit]

So, after getting the diagnosis that there were combustion gases getting into the cooling system, we decided to rip everything apart and replace the head gasket. I had the head sent to the machine shop to get tested, and it turned out being severely warped, but not cracked. It was repairable, and we'll start putting it back together tonight. I'm not sure what all was done to the head since it was warped real bad. I'm hopeful that they made sure the valves and cams were still in good shape. I don't want to have to take that thing apart again. Will update you when it's back on the road.

 

[eXplicit]

A little update in the rebuild process. Discovered that the head was milled down to compensate for the warp. Unfortunately, the machine shop has not disclosed to me how much material they've milled out. So here's my question.

After contacting a Chevy dealership and talking with one of the lead technicians there, they've told me that the TrailBlazer's cylinder head was built without the ability to be milled down in the event that the head is warped. Now obviously I'm skeptical. They could just be telling me that so I have to buy a new head for it. Has anyone had their head milled down to spec and has it worked well? I had already bought a factory thick head gasket, but have decided to buy a thicker one now that will go up to .020 if it was taken down far enough. I should be OK, right?

 

[Mooseman]

Found the section for cylinder head cleaning and inspection in the manual and it says that if it's warped more than 0.08mm (0.003 inch) to replace it. Doesn't say why. Maybe it's because of the way it's made or there isn't enough material if it's shaved down. Or maybe it's such a close tolerance between the valves and pistons that the head can't be shaved.

But reading our holy grail thread for cylinder head R&R http://gmtnation.com/f24/4-2l-i6-head-removal-engine-restoration-4425/
from what I can gather, the head was kept but it's unclear if it was shaved or not.

BTW, if you do read through the whole thread, it failed due to a screw up by the machine shop. :banghead:

 

[CaptainXL]

I would think a warped head would in most cases also have warped camshaft bores. Correction would be impossible. Perhaps that is what they are referring too?

 

[eXplicit]

Well, here's where we're at. Head went on, went to do a compression test. Got 175-180 in 1, 2, 3, 5, and 6. Number 4 ended up getting an exhaust valve stuck open. Not both, just one of them. I don't know how this happened, but at this point, it's now back at the machine shop. We'll see what happens.

 

[CaptainXL]

#4 cylinder is prone to misfire. Due to the fact that water can short out the coil. Could be part of the problem.

 

[Mooseman]

#4 cylinder is prone to misfire. Due to the fact that water can short out the coil. Could be part of the problem.

Not likely. His problem is purely mechanical with the stuck valve. Seems to be a common theme on these with rebuilt heads.

 

[eXplicit]

It ended up being a rusted valve guide because of the warp and the cooling leak. The valve went open and then wouldn't close right away and was immediately smacked by the piston on the upstroke. Turns out the machine shop only want and sonic cleaned it, resurfaced it, and pressure tested it. Ended up taking it back and having the valve replaced and had an entire valve job done. We got it all put back together today and ran it. Turns out we now have a coolant leak on the upper neck going into the head. Simple fix. The O-Ring was new on it, but it didn't hold for whatever reason. We'll replace it tomorrow. We let it run for a good 10 minutes and it kept nice and cool. I'll be able to drive it around tomorrow and get a good test on how she'll hold up. My mechanic did a great job taking it apart and putting it back together. We even put a nice coat of flat black on the oil pan, timing chain cover, and valve cover. Looks pretty nice.

 

[eXplicit]

So we're all up and running. It's going great. I'll never recommend doing another head job on this engine with it actually in the truck itself. Next time I have to do something like this, it's coming all out. It was pretty ridiculous. But it's going great now.