I have had the dreaded overheating issue since I installed a remanufactured engine. No heat out of vents, Idles at normal temp. I have changed the Tstat, radiator, and cap. Had a leakdown test performed and passed. Had a coolant HC test done and passed. Everytime I burp the system and get all the air out I will get heat from vents and run at normal temp until driven a half mile. Please feel free to chime in. Any help or insight would be greatly appreciated.

Also no smokey exhaust or milky oil.

 

If you still get air out of the system every time you burp it, then you simply haven't gotten all the air out. My understanding is that these engines need to be burped several times to get all of the air out. Don't forget there's bleed valve up near the firewall on the passenger side of the engine.

 

Water pump and fans up to snuff? Doin their jobs?

 

Let me be more clear. I have bled the system properly at least 10 times. I have jacked it up and bled it with a spill free funnel until all bubbles stop coming out and heat blows from the vent. After driven a half mile heater blows cold and engine temps rise. So recently I took it to the shop. Leak down test and HC test was done. The mechanic bled it several time with the same results. He then tried vacuum filling the system. All air was drawn from system and worked fine until the car was driven. Something is injecting air into the system it seems. According to the tests performed it's not the head gasket but what else could itbe?

 

Water pump is new and working. Fans are old but the do come on like they should.

 

Coolant temp sensor?

HC test is the pressure test? So overflow cap, crack in overflow tank or heater control valve is out of the question?

 

Hydro carbon test actually. Tests for exhaust in the coolant. A coolant pressure test was also done and it passed. Heater control valve has not yet been looked into though. I honestly don't know where it is?

 

Neither do I on this particular car, but it should have exposed a weak point in a pressure test. Had one with a tiny hairline crack in an old car that couldn't hold pressure.

I've been googling it and there are a few theories on multiple cars but no one has found a clear solution. I hate stuff like this.

One guy on an olds forum said there could be a crack in the head between the exhaust and intake port which would cause overheating but not show up in a leakdown test. I find that improbable, but not impossible. To check, you have to remove the exhaust manifolds and look for an extra clean port..? Not easy on the G. I would consider every other avenue before trying that. I'll keep thinking.

 

Head gasket?

 

Head gasket is what I'm fearing but, all the tests along with a compression check say otherwise. Not saying it can't be but doesn't seem that way. This engine only has about 60 miles on it and no symptoms of a bad head gasket.

 

What did the compression check results say? Can you tells us more info. on why you think its not a head gasket problem? To give you an example, my car blew once white smoke from the tails.

 

The shop said all 6 passed. I don't have smokey exhaust at all or coolant in oil or vise versa. No exhaust was found in coolant and a coolant pressure test shows no leaks in cooling system. I'm likely to pull the heads soon to inspect them. I just don't want to and find out they are fine ya know.

 

Yeah, all his tests suggest that its not a head gasket, (not that its a definite no) and pulling heads is expensive and labor intensive. I'd wanna be sure its not something else too.

 

I'm still hoping its not but not ruling it out. And by the way thank you all for your inputs. This has become very frustrating.

 

Honestly sounds like there's still air in the system. Was the air relief valve open while radiator was being filled up?


The spill free funnel is handy, but keep the car level when filling up and open the relief valve. The radiator cap is not the highest point in the system on these cars, making proper bleeding a serious PITA.


I realize it's frustrating, but double check your coolant filling process. Try the simple stuff before ripping your engine apart looking for head gasket leaks.


Here's the process from the FSM:

REFILLING ENGINE COOLANT
1. Install reservoir tank if remove, and radiator drain plug.
CAUTION:
* Be sure to clean drain plug and install with new O-ring.
* If cylinder block drain plugs are removed, close and tighten them.

2. Remove air relief plug on heater hose.

3. Fill radiator and reservoir tank to specified level.

* Pour engine coolant through engine coolant filler neck slowly of less than 2 (2-1/8 US qt, 1-3/4 lmp qt) a minute to allow air in system to escape.

* When engine coolant overflows air relief hole on heater hose, install air relief plug with new O-ring.

4. Warm up engine to normal operating temperature with radiator cap installed.

5. Run engine at 3,000 rpm for 10 seconds and return to idle speed.

* Repeat two or three times.
CAUTION:
Watch water temperature gauge so as not to overheat engine.

6. Stop engine and cool down to less than approximately 50°C (122°F).

* Cool down using a fan to reduce the time.

* If necessary, refill radiator up to filler neck with engine coolant.

7. Refill reservoir tank to “MAX” level line with engine coolant.

8. Repeat steps 3 through 6 two or more times with radiator cap installed until engine coolant level no longer drops.

9. Check cooling system for leaks with engine running.

10. Warm up engine, and check for sound of engine coolant flow while running engine from idle up to 3,000 rpm with heater temperature controller set at several position between “COOL” and “WARM”.

* Sound may be noticeable at heater unit.

11. Repeat step 10 three times.

12. If sound is heard, bleed air from cooling system by repeating step 3 through 6 until engine coolant level no longer drops.

* Clean excess engine coolant from engine.