Cooling system mystery
Chronic Tool Dropper
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From: Bend, Oregon
Ron--
Pressure check the system with what you have in there now. It's a simple test, definitive. Water will leak out, and you'll be able to crawl around and find the leak without risk of getting burned by hot motor parts or coolant. On a hot motor, a straight water leak may not be visible until it cools off a little anyway. Cooling system pressure tester is often free with a deposit at popular parts stores. Takes minutes to pump and test.
Pressure check the system with what you have in there now. It's a simple test, definitive. Water will leak out, and you'll be able to crawl around and find the leak without risk of getting burned by hot motor parts or coolant. On a hot motor, a straight water leak may not be visible until it cools off a little anyway. Cooling system pressure tester is often free with a deposit at popular parts stores. Takes minutes to pump and test.
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From: Calgary Canada
This may have allready been covered but I had a coolant leak that came out near the cats. Turned out to be a crack at the bottom of the coolant resovoir which under pressure went down the fire wall onto the belly pan and out the vents by the cats. Its hard to detect because of the very tight quarters. Was worse as pressure built up. I removed the tank and repaired the crack succesfully.
Chronic Tool Dropper
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Cracked reservoirs are too popular as the cars age. Fixing one crack is a stopgap (literally) while you wait for it to crack in another place. Considering that they are rather inconvenient to replace, I'm not sure I'd be willing to take it in and out a few times to do temp fixes on it. I did a similar field repair on another car, welding it using a soldering iron and using tie-wraps for 'filler' in the welds. It held up long enough to get the new reservoir ordered and delivered from Sweden. Why risk getting stranded someplace with a cobbled part?
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928 Barrister
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From: Sunnyvale, CA
Well, I have installed new hoses to/from the heater core and heater valve. Grunted and groaned on a couple of the hose clamps but its done. I didn't change the valve, and now wish I had, but it seemed ok, and is an Audi metal valve. I used the heater on the drive back to Sunnyvale and no problems seemed to develop. The radiator side tank leak has also vanished, so I will just hold on to the new side tank and gasket I bought for now. Tomorrow I take the car on a longer drive and will monitor it closely.
The hoses I removed appeared to be in reasonably good condition though a little swollen around the clamps, and the clamps were all ok. When I return Dave, I would like to take you up on that pressure test session. I couldn't find anyone who would loan or rent a pressure tester so I will probably have to buy one. As for my reservoir, it is yellowed and probably should be replaced. It certainly doesn't seem to leak when it is just sitting and I keep the cap only tightened one click when it is running. Of course the pressure can still build in a warm engine so I can check it from time to time. I can't find any evidence of a leaking reservoir presently.
The sage continues.....
The hoses I removed appeared to be in reasonably good condition though a little swollen around the clamps, and the clamps were all ok. When I return Dave, I would like to take you up on that pressure test session. I couldn't find anyone who would loan or rent a pressure tester so I will probably have to buy one. As for my reservoir, it is yellowed and probably should be replaced. It certainly doesn't seem to leak when it is just sitting and I keep the cap only tightened one click when it is running. Of course the pressure can still build in a warm engine so I can check it from time to time. I can't find any evidence of a leaking reservoir presently.
The sage continues.....
Chronic Tool Dropper
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Run,
The system needs to be run under pressure (cap screwed on completely) to maintain proper cooling. The system will build vapor/steam bubbles and lose cooling at those hot places in the blcok, just exactly where you need proper heat transfer the most. Put the cap back on tight, and find the leaks with it under pressure. It won't leak any more water that way than it will with the cap loose and bubbling over.
The system needs to be run under pressure (cap screwed on completely) to maintain proper cooling. The system will build vapor/steam bubbles and lose cooling at those hot places in the blcok, just exactly where you need proper heat transfer the most. Put the cap back on tight, and find the leaks with it under pressure. It won't leak any more water that way than it will with the cap loose and bubbling over.
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928 Barrister
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From: Sunnyvale, CA
Run,
The system needs to be run under pressure (cap screwed on completely) to maintain proper cooling. The system will build vapor/steam bubbles and lose cooling at those hot places in the blcok, just exactly where you need proper heat transfer the most. Put the cap back on tight, and find the leaks with it under pressure. It won't leak any more water that way than it will with the cap loose and bubbling over.
The system needs to be run under pressure (cap screwed on completely) to maintain proper cooling. The system will build vapor/steam bubbles and lose cooling at those hot places in the blcok, just exactly where you need proper heat transfer the most. Put the cap back on tight, and find the leaks with it under pressure. It won't leak any more water that way than it will with the cap loose and bubbling over.
I will tighten the cap all the way and drive it tomorrow in the heat. I'll monitor the level in the reservoir. I also plan to replace the heater valve simply because it has been in there at least three years. I doubt the reservoir is the problem, but I will also replace that after the valve as a matter of preventive maintenance. So far the system is holding water since I replaced the hoses. I hope it continues to do so.
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From: Boulder Creek, CA
Ron, next thing to try is tighten the cap all the way, then drive it in hot conditions, heater full on(fan on lowest setting) and run it hard enough to generate the heat you need to pressurize the system. A quick run up 280 at about warp 5 to Alpine Rd and back will get it nice and toasty. 
Or we can still do the pressure test if you like.
Or we can still do the pressure test if you like.
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928 Barrister
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From: Sunnyvale, CA
Thanks Dave. Today I kept the AC on from Milpitas to Sunnyvale, and had water level remain consistent, and I was running reasonably hard from Placerville to Milpitas, as well as an hour and a half along the I-80 corridor from Sacto to Fairfield which is hell on Earth during a weekend: 40 miles in 1 1/2 hour in 90 degree weather doesn't do much for cooling. Then the sprint home from Fairfield. I think I gave it all I could to force a leak but it held steady. I agree about the heater, and will try to do a 280 run this week.
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928 Barrister
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From: Sunnyvale, CA
I still have to replace the passenger side tank. It seems to strangely have ceased leaking, though it was merely a slight drip. I will replace it anyway, before it becomes a major drip.
Chronic Tool Dropper
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Does anybody else remember the famous anti-freeze ad, the one where they poked holes in the metal anti-freeze container with an ice pick? ('Metal Can' should be a clue to the age of the quastions...) Stuff runs out the holes for a bit then slowly stops. Ad is touting the leak-stop capabilities of the product. In court later, they suggest that any fool can see that after it leaks a while, it will finally stop when there's no more coolant in there. Apparently the judge wasn't just "any fool", and Union Carbide (who made the coolant in question) had to fork over a bunch of money to plaintiff class-action attorneys and some pennies to those who were actually damaged. Many people were still steamed.
