Air in coolant?

[gervin]

So for weeks I have been battling what I think was air stuck in the coolant. I have been letting the engine get up to normal temp while running the heater then adding more coolant once I can safely get the radiator cap off. I do this until it won't take anymore. Now here is the problem. This morning I start the car up and start driving. Coolants starts spitting out the over flow tank within the first 2 minutes of the car running. You would think that just meant that there was a little too much coolant and it was just leveling its self out, but it spits out too much and causes over heating. Anyone ever had a problem like this?

Oh and the Tercel got stuck this morning for the first time since I have had it! There is 2 feet of snow on the ground and its just too deep for the little wagon

[danzo]

To me it doesn't sound like your coolant overflow caused the overheating, it may be the other way around. You probably don't have too much air in the system - your car is overheating for another reason and thus boiling its fluid. If your t-stat and water pump are OK, then I would do a compression test. You might have a blown head gasket. What does your oil look like?

Hope this helps, good luck and keep us posted.

[gervin]

To me it doesn't sound like your coolant overflow caused the overheating, it may be the other way around. You probably don't have too much air in the system - your car is overheating for another reason and thus boiling its fluid. If your t-stat and water pump are OK, then I would do a compression test. You might have a blown head gasket. What does your oil look like?

Hope this helps, good luck and keep us posted.

Ya T-Stat is brand new and seems to be properly working. I'm pretty sure the water pump is working, it's not leaking or anything. Any easy way to test it?

I know the head gasket isn't blown, I have checked the oil and everything.

[danzo]

If your waterpump isn't leaking then it's probably working. About the only thing that comes to mind is that you have an incorrect and/or faulty radiator cap. It may be letting pressure into the overflow tank at too low of a pressure. What is the psi rating on the cap? How old is it? If it's OK then I would check the routing of the coolant lines - just throwing this out there, they are prolly correct.

This thread reminds me of a product I have been searching for. I would love to have a see through filter that can be spliced into a coolant hose. Similar to a glass fuel filter but of course much larger. I just can't believe no company makes it, in fact I know they exist for big diesel trucks. JC Whitney and Jeg's don't have it, can anybody help? It would be so useful.

Sorry to highjack your thread, gervin.

[gatemaster]

I am having a similar problem. Exhaust is getting into the water, but water is not getting into the oil. But I am getting some wierd type of oily stuff on my radiator cap. I retorqed the cylnder head which fixed the problem but it came back about a week later. Also I am having to top off the radiator every so often. Nothing leaks, so where does the water go. It goes into the air filter as water vapor via the pcv valve or other type connections. I have a weber and when I take the air filter top off there is water collecting around the bottom of the air filter assembly. so I have to replace the head gasket.

[takza]

Cylinder head gasket?

TEST: start engine up COLD...remove rad cap...be sure coolant is topped up....watch closely for bubbles. If you see a stream of them...you have an exhaust into coolant leak. When these get real bad they cause overheating due to the added heat of the exhaust in the coolant.

[sdoan]

This is exactly what my rebuilt 4A did. I'd make sure the cooling system was absolutely full - park on hill to fill radiator, bleed any air out of a fitting in the heater hose - and the next time I checked the radiator would have air in it.

If it was absolutely full and I started the engine the overflow tank would fill almost immediately and there would be new air in the cooling system. I drove it to Las Vegas and back this way 4000 miles! And over mountain passes and the whole thing. If I kept it full it didn't over heat, but every time I stopped more air would get in and more coolant would come out. After several stops the temp gauge would get very high, but it never boiled.

I finally figured out that it was a bad head gasket. This was with a brand new gasket, surfaced head, retorqued head bolts and I did the work - but it was a cheapo head gasket that had come in the rebuild kit . Get a Felpro or Toyota head gasket.

Here's how I found it: I finally realized that the air was getting into the cooling system as soon as I started the engine. So I disconnected the distributor lead and found that the air would get into it just by cranking it over. Then I pulled all the sparkplugs and cranked it over - no air! So I put in one plug and tried again, no air. Put in another plug and tried again, no air. I did get air when I put the 3rd and 4th plugs in - the leak was between the water passage and both cylinders 3 and 4.

Apparently the gasket formed a water-tight seal, even under 12 lbs pressure, but it would not hold the 170 lbs pressure of compression. The weird thing is that the gasket seemed to seal as soon as the engine warmed up a little - heat and expansion of the head caused the gasket to seal better

Replaced with a Felpro head gasket and haven't had any problems since.

Let us know what you find.

[Petros]

i even had a leaky head gasket that would compression test okay, all the pressures during a compression test were the same and high. But I lost water like this, a little at a time. I just kept refilling it, even if leaky, as long as there is water in it, it will cool okay.

BTW. the combustion pressures when the spark plug fires is closer to 2000 psi, not the 170-180 when you do a compression test. So you are asking the gasket to do a lot, especially between cyl 1 and 2 and between 3 and 4 where it is real narrow.

Do you have a lot of steam coming out of the exhaust? Kind of hard to tell when it is that cold since the normal water vapor from combustion condenses in very cold air anyway, but see if it seems higher than normal. Make sure your radiator is cooling properly, not plugged or filled with sludge or rust, all the hoses are not pinched. And you have a good cap. If so it may indeed be the head gasket.

[gervin]

Ya it's getting to the point where it almost has to be the head gasket

I guess in the long run it will be a good thing because I wanted to do a rebuild on the whole thing anyways.

I will keep you guys updated.