Coolant overflow and overheating

[hbasavar]

93 Camry Wagon V6 3VZ-FE.

Problem description. There is huge overflow into the coolant overflow tank and I see a lot of air blocking the coolant flow. When I do a complete refill, it runs for a while smoothly without over heating and then the air block happens.

I have changed both my Rad caps. (one on the rad and the other on the top of the engine block to the radiator).

I am pretty sure it is not exhaust gases coming out as I did a HG job and am positive that I am not losing coolant. I have put close to 1000 miles on it already and I had this problem since the HG job. I am guessing I should have lost all the coolant by this time if it were to be the exhaust gases. I could still be wrong totally.

I spent an hour yesterday running the engine with the radiator caps off. Initially with both off and then once it came to overflowing I closed the one on top of the rad and left the top one open and observed. It overflowed quite a bit which I kept sucking it out and even when the levels stabilized and the system was circulating fully, there was clearly air bubbles still coming out. They just wouldn't stop. I have burped the system very well as I ran the engine for more than 45 mins with the cap off. The bubbles won't stop.

Is it possible that outside air is being sucked into the system as the pump runs? O ring around the water pump? hoses?

Any ideas how I could go about troubleshooting this issue?

Your responses are most appreciated.

Thanks,
Hemanth

[Stillrunning]

The system is under pressure so I doubt it is sucking air. Although as it cools it will suck back into the system, but through the overflow tank. If it were sucking air it would leak at the same spot. Did you have similar problems when the HG needed to be replaced? Can you smell exhaust gas in the coolant (please make sure it's cold first )? There is a test kit I think you can get from Advance, etc. to test coolant. Is there any thick white smoke coming out the tail pipe? Did you have the head checked for cracks before you put it back on? Why did the HG blow? Looking at a cracked head at the exhaust is not a bad theory since it would see constant pressure from the exhaust and not leak coolant. As the head cooled the crack may close up and not show any coolant loss.

[sbushnak]

I used to have the exact same problem. Now my car has 129xxx miles on and the previous owner replaced the head gasket when the car had 90xxx miles.

When my car overheated, I changed the thermostat, rad caps, and then flushed the cooling system. The problem went away.

Good luck.

[hbasavar]

No white smoke in the exhaust. I had that before and I can surely tell that one. But if the coolant loss is so small then it might be harder to tell in the exhaust.

I will try again, if I can smell exhaust gas in the coolant. Air bubbles are clearly there when the engine is running. Yes, the head was checked in a body shop for cracks and shaved before they were put back on. But I am not sure of the block itself. But the body shop guy told me that it is a cast iron block and would not crack.

HG blew when I was trying to do a coolant flush and an air gap in the system did not circulate the coolant properly. That was my first job and I didn't know what I was doing, stepped out with the car running to take a call and it was all boiling when I came back. It is quite possible that the prev owner knew about some hg problems as the coolant was muddy. He probably tried to use additives to fix hg leaks.

I do have an easy way out of this. I could cut out the rubber on the top pressure cap so that it won't seal properly. The air escapes out but the system will never be pressurized. I know the boiling point of the coolant rises but constant coolant circulation will be there. What do you guys think of that?

Thanks,
Hemanth.

[hbasavar]

Can you guys tell me the pressure rating on the rad caps?

The rad cap on the radiator is 1.1 the pressure cap I am not sure.

I have both on at 1.1. The old ones were rad cap 1.1 and pressure cap 1.0.

Will that make any diff?

[Stillrunning]

Removing the rad cap seal will lower pressure and LOWER boiling point. I don't think you're going the like that either. You may boil it when you shut the engine down as the heat rises, the coolant may boil and blow out the overflow. Adding more A/F will raise the boiling point. I believe the rad cap is to be rated at about 14psi. The Stant replacement is rated at 13psi. When the head was shaved did you make sure the head bolts were not too long to torque properly?

[hbasavar]

Sorry, I did mean lowering the boiling point.

The head was shaved probably a 1/10 mm thickness off. The bolts did fit in correctly and I did torque to around 28 ft/lbs. The manual says around 25.

This has been too much of frustration for me. Emissions failed and then the Head gasket. Now the overheating.

[davemac2]

Originally Posted by hbasavar

Sorry, I did mean lowering the boiling point.

The head was shaved probably a 1/10 mm thickness off. The bolts did fit in correctly and I did torque to around 28 ft/lbs. The manual says around 25.

This has been too much of frustration for me. Emissions failed and then the Head gasket. Now the overheating.

Head bolts torqued to 28 ft-lbs??!! Seems way too low to me. Should be more like 50-60 ft-lbs. Did you re-use the old bolts or get new ones? Did you follow the latest tightening sequence recommended by the gasket manufacturer and lubricate the bolt threads, clean the threads on the block with a tap? Your problem sounds like a leaking head gasket to me.

Edit: looking in the factory manual, I see it does say 25 ft-lbs for the inital torque, but then each bolt must be turned an additional 180 deg. in 2 90 deg. steps. Did you do that? I would imagine the final torque with this sequence would bring it up past 60 ft-lbs.

dave mc

[toyomoho]

If you think it is a head gasket leak, you can test for exhausts gases in the coolant.

http://www.arrowheadradiator.com/hea..._leak_test.htm

[hbasavar]

I did reuse the head bolts and I did lubricate the bolt threads before I put them on. I did clean the threads on the bolt but I do not have a tap and couldn't do the threads on the head.

I am sure that I did tighten the bolts pretty tight to the extent that it started giving a squeaking sound. Over tightening is not recommended either as you are running the risk of crushing the gasket and the heat will only crush more.

Any leaking gasket would immediately result in coolant loss and at least some white smoke in the exhaust. The bubbles are not starting up immediately and not until the water pump start working.

Is there a possibility that it is sucking air from outside probably near the water pump or the thermostat?

[Stillrunning]

If you go with the idea that it is sucking air then you would have to believe the system is creating lower pressure for the air to be forced into the system from higher outside air pressure. The suction side of the water pump would be the only logical place - but the water pump is really just a circulating pump, not a postive pressure pump. If there was a restriction at the suction side of the pump, collasped hose, blocked rad, closed thermostat, then the intake of the pump could see reduced pressure, but there is a by-pass that should compensate for presssure difference. When the engine is cold and the thermostat is closed the system does not produce significant lower pressure at the pump inlet or the lower rad hose would collapse. Once the system heats and pressures rise above ambient air pressure any leak from the outside should show up as a coolant leak.

[hbasavar]

Thanks for a clear explanation. I will look through for any coolant leaks after opening the radiator caps. If I don't open the rad caps the pressure might just hold the coolant and may not leak any.

I will keep you posted.

[hbasavar]

Update: Today I just ran it again with the top pressure cap off and observed the air bubbles. Once the engine started, the air bubbles were there and the coolant was instantly hot indicating that these were exhaust gases. The bubbles were very small to mid size and they kept coming. After about 15 - 20 min, the bubbles stopped. This indicates that the heat expanded head closed the gaps and mated well with the gasket and the block.

As I see there are two possibilities. One is that the head bolts are not torqued enough(thanks to dave mc) and may be retightening them some more might fix this. Another is the dreaded head warpage/crack in the block (head was checked and it wasn't cracked).

Please let me know if you seem to agree with my analysis. Always helps to have someone concur.

Thanks to everyone who has responded.

[Stillrunning]

Doesn't matter if we agree, the low cost attempt at a fix is to re-torque the cyl'd head. Do that first then see what happens.