Overheating, Please help before I give up and sell

[Greichert951]

Ill try not to write a novel, please bear with me. Started a couple months back that I realized my temp will occasionally climb over the typical 210 while in traffic or sitting still. Hits 220-230, fans come on and temp comes right back down. Then a few weeks ago, trans blew out. Hasn't felt great since I've owned it so I wasn't that surprised. Rebuilt trans from transmission authority and feels better than before but still sloppy shifts. (I'll revisit this) Anyway, now that the new trans is installed, I've been keeping a close eye on the trans temp. which has seemed high from the start. Installed an aftermarket cooler which has kept temps lower but still eventually creeps ups to low 200's which I feel is un-acceptable for typical in town/highway driving with no load. Started troubleshooting the engine cooling system to see if the two problems were connected. Turns out lower hose is ice cold. New thermostat (yes, tested in pot of water), flushed engine, radiator, heater core and all hoses, and still ice cold even though engine and upper hose are hot as hell. Now I'm thinking trans overheating is due to heat transfer from overheating engine. I'm running out of patience and money, what else could cause the high temps and cold hose? Any help would be greatly appreciated! Thanks in advance.

[Spurshot]

Some things come to mind I'd check. Verify the thermostat is installed in the correct OEM orientation, not just how you found it. Check the radiator for flow blockage and some kind of Sealant that someone may have used.

[Btuggle88]

Sounds like you might have an air pocket trapped, there is a vacuum you can put on it to pull the excess air out.

[Greichert951]

Thanks for the quick replies. Spurshot, I questioned the thermostat orientation as well but I have it in the factory orientation with the body facing down toward the engine. I actually don't think the therm. housing is even deep enough to allow for backwards installation. And the radiator allows full flow from a garden hose to pass with ease although im sure this doesn't rule out the possibility of some restriction. I'm tempted to replace the radiator anyway and that may be my next step.

 

Btuggle88, air in the system was my other theory so I've tried to burp the system a couple of times. This is when I discovered the cold lower hose. I would let the engine get to 210 on the gauge and by the time the engine and upper hose were radiating massive heat, I felt it necessary to shut down (lower hose still cold). I finally just let it keep running today while attempting to burp again and it eventually boiled over but the lower hose did eventually get hot. I'll look into buying the vacuum pump just to be sure but I've never heard of the standard burping method failing the do the trick. WTF is going on with my truck?! It seems to me that it's a problem with flow so I'm leaning heavily toward a new radiator but I'm still skeptical.

[intheburbs]

Bad water pump?

[j-ten-ner]

How many Kilometers do you have on your truck?

 

http://www.gm.ca/gm/english/services/certifiedservice/schedule/model?vehicle=2007_chevrolet_silverado

 

240,000 km
Engine cooling system service (or every five years, whichever occurs first). An Emission Control Service. See footnote (i)

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.

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(i)

Drain, flush, and refill cooling system. This service can be complex; you should have your dealer/retailer perform this service. See Engine Coolant for what to use. Inspect hoses. Clean radiator, condenser, pressure cap, and filler neck. Pressure test the cooling system and pressure cap.

 

so long

j-ten-ner

[Greichert951]

Thanks for the suggestions. It does seem like no/low water flow is the problem burbs, but I think the water pumps only possible failure is leaking. Correct me if I'm wrong, but as long as these pumps don't utilize a plastic impeller, they should always be pumping water as long as the pulley is spinning, which it is. Also the upper hose, overflow tank and both heater core hoses being hot makes me believe that the pump is doing its job. It screams thermostat not opening in my opinion but I tested it and am absolutely positive that it opens properly.

 

It has just shy of 100,000miles j-ten-ner. And i appreciate the info on the cooling flush but the problem started before that. I only flushed because I was already changing the thermostat but I'm going to order the vacuum fill rig just to be sure.

 

Still leaning toward restricted radiator flow but I'm all ears to everyone's info and suggestions. Thanks again!

[sahls01gmc]

I noticed after you got your new transmission that you never said it got back up to the 220-230 range. My truck runs at just under 210 degrees in everyday driving. Stays just about the same when towing. Your truck should be just fine if it is running around 200 and not going higher. Air in the system can definitely cause issues, so make sure you have burped it as much as possible.

 

I would lean towards a radiator issue if you are describing the ice cold lower hose correctly. I'd take it out and a have a shop take a look at it.

[Greichert951]

Sahl, the engine temp. does still get up to the 220-230 range but only while sitting still or in traffic with the AC off. The transmission temp is mostly under control now that I put the auxiliary cooler on it but the engine temp just isn't right. I've had this truck for about three years and the overheating while sitting still just started within the last couple of months and seems to be getting more frequent. For what it costs to have the radiator flow tested, I'm probably just gonna put a new one in there and see what happens.

[sahls01gmc]

Ok, that makes sense. Just making sure I understood correctly. I agree, a new radiator isn't much more than getting yours looked at. It's gotta be the radiator, water pump or thermostat. Keep us informed as you figure this out.

[Greichert951]

Agreed, there's not much to the cooling system. It has to be one of those things. I'll definitely keep everyone posted though and thanks for all of the advice! I appreciate everyone's input immensely.

[_matt1313]

Run it with the overflow cap (in driveway) and wait for thermostat to open the waterpump will push water up into and out of over flow and remove air pockets. Burp the system.

 

If this doesn't happen you have blockage or a bad water pump.

 

All in all your temp is good

[Greichert951]

Matt, I assume that you mean to run it with the overflow cap OFF, correct? This is the burping procedure that I have tried but the engine eventually gets so hot that it boils over. It seems that you're right about the blockage or bad pump but has anyone heard of a water pump failing on these trucks? I think the only possible failure of the pump is leaking but I could be wrong about that. It seems to me that the pump is trying to flow but something is stopping it. That's why I said that the symptoms scream bad thermostat but I'm sure that it opens properly. I'm gonna order the new radiator and hope that it fixes the problem.

 

Also, what do you mean that my temp. is good Matt? It never used to fluctuate up to 230 before. Why would it do it now? And my front end is burning hot which it never used to be. Something is definitely wrong, I just can't figure out what.

[_matt1313]

Have checked engine oil? Any coolant? Pull lower hose use a flash light look up pump for debris

[Greichert951]

Engine oil was changed fairly recently (always Mobil 1), is at the correct level and has no signs of coolant in it. Looking up the pump for blockage is something that hasn't been suggested yet. I'll check that out, although I did back flush the pump without issue.

 

New radiator has been ordered by the way. It seems that the problem is getting worse. I don't even need to be stopped for long for it to overheat now. Pulled into the drive through ATM today and it was creeping over 210 before I could even stop rolling.

 

Thanks for all of the suggestions everyone! Each thing that I rule out is one step closer to figuring out the problem.