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post #61 of 76 (permalink) Old 12-10-2012, 06:37 PM
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Just brainstorming here . . . does air have to be drawn into the cooling system to result in bubbles in the overflow. I believe not. Even coolant of the correct concentration and under 12 psi pressure has a boiling point. And, if it boils, there's bubbles, and the bubbles are carried by the flow to the top of the radiator and out the rad cap to the overflow.

Boiling of coolant can happen around the upper cylinder walls and head if the flow is inadequate. This is normally prevented by having the pump designed to circulate the coolant at a high enough rate, even at idle. It's also why the heater circuit is constant flow even when the thermostat is closed -- otherwise, in these engines, there no circular path for coolant to flow inside while the thermostat is closed.

Water pump? Could be -- perhaps a loose impeller or corroded impeller not pumping well enough. (These have been mentioned earlier.) I also seem to recall a case where the timing belt was slightly loose for some reason -- not enough to cause timing problems (because of the "toothed" belt) but enough to allow the smooth back of the belt, which drives the pump, to slip.

Incidentally, I'm thinking that the problem of boiling is made worse when the heater core is in the loop because it isn't exactly a "full flow" device. But when it's bypassed, what limited coolant circulation there is has a better chance to limit the boiling. Air in the coolant isn't a good heat conductor, so the more boiling, the more bubbles and the hotter the coolant can get. In this case, even if the thermostat is open, the limited circulation won't be sufficient.

In regard to the chemical tests, are you using it at the overflow reservoir or at the radiator neck (where the cap would be)? If the former, I wonder if that could be affecting the readings. The air would be passing through the relatively cool coolant in the reservoir. Perhaps temperature affects the way the chemicals react.

Again, just brainstorming . . .
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post #62 of 76 (permalink) Old 12-11-2012, 01:00 PM Thread Starter
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Originally Posted by Glennda5id View Post
You did an exhaust chemical test and the air coming out of the overflow is not exhaust? There is literally nothing else it could be.

There needs to be sufficient exhaust gas to get the liquid in the test kit to change color. Are you revving the engine when doing the test.

Our systems are self bleeding and there should be a gas bypass on the thermostat. If you have that much air in the system you most likely have a HG issue.

I would say with 99% certainty that you have a HG issue. Your symptoms fit the HG issue exactly.

Also you will not get mixing of oil and coolant. Coolant is not being pulled into the cylinder. When the cylinder fires, the extreme pressure combined with the failing HG pushes exhaust gas into the coolant system. That cause two things. It starts to raise the temp of the coolant and it pressurizes the coolant. The pressurized coolant only has one place to go and that is out of the overflow tank.
I know, its crazy.... I warmed up the engine and did the test at idle and at higher RPMs, negative, then I drove the car around until it was nice and hot and did the chem test from the overflow. I did this because there was a pretty steady stream of bubbles in it and I figured that had to be exhaust, negatve.

I'm curious why when I bypass the heater core, although I still have bubbles in the overflow, it doesn't overfill the overflow and the engine doesn't overheat. With the heaer core in the loop it does.
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post #63 of 76 (permalink) Old 12-11-2012, 01:05 PM Thread Starter
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Originally Posted by plain OM View Post
Just brainstorming here . . . does air have to be drawn into the cooling system to result in bubbles in the overflow. I believe not. Even coolant of the correct concentration and under 12 psi pressure has a boiling point. And, if it boils, there's bubbles, and the bubbles are carried by the flow to the top of the radiator and out the rad cap to the overflow.

Boiling of coolant can happen around the upper cylinder walls and head if the flow is inadequate. This is normally prevented by having the pump designed to circulate the coolant at a high enough rate, even at idle. It's also why the heater circuit is constant flow even when the thermostat is closed -- otherwise, in these engines, there no circular path for coolant to flow inside while the thermostat is closed.

Water pump? Could be -- perhaps a loose impeller or corroded impeller not pumping well enough. (These have been mentioned earlier.) I also seem to recall a case where the timing belt was slightly loose for some reason -- not enough to cause timing problems (because of the "toothed" belt) but enough to allow the smooth back of the belt, which drives the pump, to slip.

Incidentally, I'm thinking that the problem of boiling is made worse when the heater core is in the loop because it isn't exactly a "full flow" device. But when it's bypassed, what limited coolant circulation there is has a better chance to limit the boiling. Air in the coolant isn't a good heat conductor, so the more boiling, the more bubbles and the hotter the coolant can get. In this case, even if the thermostat is open, the limited circulation won't be sufficient.

In regard to the chemical tests, are you using it at the overflow reservoir or at the radiator neck (where the cap would be)? If the former, I wonder if that could be affecting the readings. The air would be passing through the relatively cool coolant in the reservoir. Perhaps temperature affects the way the chemicals react.

Again, just brainstorming . . .
Sounds logical to me. I suppose the bubbles could be just coolant boiling and boiling caused by poor flow. I've heard of others having issues with the timing belt tensioner. When I did my timing belt, water pump and tstat I didn't change it. Anyway to tell, without removing it, if the tensioner is shot?
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post #64 of 76 (permalink) Old 12-11-2012, 01:19 PM
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Sounds logical to me. I suppose the bubbles could be just coolant boiling and boiling caused by poor flow. I've heard of others having issues with the timing belt tensioner. When I did my timing belt, water pump and tstat I didn't change it. Anyway to tell, without removing it, if the tensioner is shot?
Heater core must be restricting flow or have a leak in it causing the over heat issue.
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post #65 of 76 (permalink) Old 12-11-2012, 01:52 PM
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If you bypass the heater core are you blocking the bypass hose that comes off of the water pump by the thermostat?

50/50 coolant at 15 PSI will not boil until 280+ degrees. The bubbles are not steam bubbles.

Regarding the test. I have used the Napa test and it required a good bit of exhaust gas to set it off. I would recommend getting the engine hot until you see a steady stream of bubbles and then let it sit and keep pulling air from the overflow through the test fluid.
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post #66 of 76 (permalink) Old 12-11-2012, 02:27 PM Thread Starter
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Originally Posted by Glennda5id View Post
If you bypass the heater core are you blocking the bypass hose that comes off of the water pump by the thermostat?

50/50 coolant at 15 PSI will not boil until 280+ degrees. The bubbles are not steam bubbles.

Regarding the test. I have used the Napa test and it required a good bit of exhaust gas to set it off. I would recommend getting the engine hot until you see a steady stream of bubbles and then let it sit and keep pulling air from the overflow through the test fluid.
No, the bypass is simply taking he heater core inlet and outlet hoses and connecting them together using a 3/8 coupler.

I picked up the test kit from Autozone and used almost a complete bottle of the solution running the test a number of different ways including getting the engine hot, witnessing a steady stream o bubbles and testing in the overflow.
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post #67 of 76 (permalink) Old 12-11-2012, 02:33 PM
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These test kits are generally pretty accurate if the issue is a head gasket allowing exhaust gasses into the cooling system. I suspect that is not your issue due to the multiple tests showing no such case.

You have a leak some place allowing air into the system
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post #68 of 76 (permalink) Old 12-11-2012, 02:58 PM
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Quote:
Originally Posted by Glennda5id View Post
If you bypass the heater core are you blocking the bypass hose that comes off of the water pump by the thermostat?

50/50 coolant at 15 PSI will not boil until 280+ degrees. The bubbles are not steam bubbles.

Regarding the test. I have used the Napa test and it required a good bit of exhaust gas to set it off. I would recommend getting the engine hot until you see a steady stream of bubbles and then let it sit and keep pulling air from the overflow through the test fluid.
I've never used the test, but from a youtube video - it does seem the color change is quite subtle.

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post #69 of 76 (permalink) Old 12-11-2012, 08:29 PM
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. . . 50/50 coolant at 15 PSI will not boil until 280+ degrees. The bubbles are not steam bubbles.. . .
That is correct, but aren't combustion temperatures many times the boiling point? The heat from combustion has to be absorbed and carried away or the engine will fail. If the coolant surrounding the cylinders and head isn't moving sufficiently (i.e., isn't carrying the heat energy away from those surfaces) it seems to me that the coolant temperature can rise well above it's pressurized boiling point.
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post #70 of 76 (permalink) Old 01-08-2013, 02:35 PM Thread Starter
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Fixed!

So, I fixed the problem. Purchased a 2003 OB w/ 56K miles that just had the heads rebuilt. Like brand new. The 2001, I think, has a cracked block and I was just tired of messing it with.
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