is it the headgasket?

Mostly copied from my E-mail to JD, and also crosslinked with Turbobricks. I can't seem to keep coolant in my 91 Volvo 940.

Two months ago it was the upper radiator hose. No big deal, the local parts store even had one in stock. Then it was the expansion tank hose. Two weeks ago it was the heater core hose. I bought it online and a 'Close enough' at a local parts store for temporary use. Got the permanent one on there and now the seal on the upper part of the water pump blew. At the dragstrip. In the staging lanes. Before making a pass. It eventually ran a 9.46, though. Nobody even has a part number locally, and it's some oddball flanged square O ring weirdo thing that was dry rotten to hell. Now it's out of commission while one ships in. A $3 part is keeping it at home for days. I can't wait to find out what coolant related failure happens next!

Is it the head gasket pressurizing or is this just unrelated, 'your rubber is old' stuff?

Thanks -Brian

Sounds like old rubber. Either that or you radiator cap is allowing a system overpressure.

I would consider going ahead and replacing the cap in case it isnt venting at too high of a pressure (preventative maintenance)

Apexcarver wrote: Sounds like old rubber. Either that or you radiator cap is allowing a system overpressure. I would consider going ahead and replacing the cap in case it isnt venting at too high of a pressure (preventative maintenance)

Yeah...your cap is what, maybe $15?, and it can cause all sorts of grief if it doesn't work right. Just the sort of stuff you're currently finding the weak points in, BTW...

Good luck!. Hopefully you've found the last of the bad stuff.

Is your coolant cap grey or black? Ditch it for the green one. The other colors have a history of overpressure failures.

It's green. I don't understand radiator caps in this application, though. Seriously. If the cap is on top of the expansion tank, how does the system care? What does it do, just vent to atmosphere? Seriously?

$50 at NAPA for a hydrocarbon block dye kit, pretty effective in diagnosing a HG leak, though a proper leakdown is best if you have an air compressor, just buy a kit but they're more $$$ (there's a cheap low pressure tester but it's not very good at finding leaks IMO at Harbor Freight)...

Raze wrote: $50 at NAPA for a hydrocarbon block dye kit, pretty effective in diagnosing a HG leak, though a proper leakdown is best if you have an air compressor, just buy a kit but they're more $$$ (there's a cheap low pressure tester but it's not very good at finding leaks IMO at Harbor Freight)...

I know it's killing me that the gasket, the bolts and the valve cover gasket only cost $60 shipped though, $50 is a lot for me!

Oh - and the obvious - no water in the oil, no oil in the water, no boiling coolant at idle in the cold motor, no large plume of white smoke...

tbricks thread

http://forums.turbobricks.com/showthread.php?p=3404309#post3404309

sounds like my "new" 91 saab. With 224,000 miles on it.. all the hoses are swollen and seemingly original (they have saab part numbers on them still) and after losing two in a week, I am replacing them all

Gates used to say "replace all hoses and belt every 5 years"

But no one does.... Yell my 92 geo made it 230,000 (14 years) on the OEM hoses

Nope, it probably isn't the headgasket. It was the radiator cap. I tested it tonight with my junky 12V compressor. The "new" one JD threw in his pile o' spares did much better under this test. The old one barely leaked at all when tested up to 25 psi. Thank God for a cool schrader fitting at work that I could clamp into the coolant lines.

tuna55 wrote: Nope, it probably isn't the headgasket. It was the radiator cap. I tested it tonight with my junky 12V compressor. The "new" one JD threw in his pile o' spares did much better under this test. The old one barely leaked at all when tested up to 25 psi. Thank God for a cool schrader fitting at work that I could clamp into the coolant lines.

Sucks it failed, glad the spare is better. Very glad I threw in a carload of parts! Since you have a tester and they aren't as expensive as a head gasket I'm wondering what a new one would test at.

My 89 has a gray cap and is starting to develop some leaks-time to get the right cap!

Junkyard_Dog wrote:

tuna55 wrote: Nope, it probably isn't the headgasket. It was the radiator cap. I tested it tonight with my junky 12V compressor. The "new" one JD threw in his pile o' spares did much better under this test. The old one barely leaked at all when tested up to 25 psi. Thank God for a cool schrader fitting at work that I could clamp into the coolant lines.

Sucks it failed, glad the spare is better. Very glad I threw in a carload of parts! Since you have a tester and they aren't as expensive as a head gasket I'm wondering what a new one would test at. My 89 has a gray cap and is starting to develop some leaks-time to get the right cap!

My official super nerdy tester consisted of the following:

One Volvo 940

One 1/2" carriage bolt wrapped in duct tape (for smoothness and diameter)

One old 6mm ish bold from a Civic (I think)

One emergency "fill up your tire once in a while" compressor running off 12V

One cool schrader bulkhead fitting borrowed (really, I'll return it) from work. We use 'em as test points.

Shove the big bolt in the big hose and clamp. The little bolt in the little hose and clamp. Take the other little hose off of the top of the radiator and clamp in the schrader valve thingie. Hook up the compressor. Count the number of seconds from 0 psi to 25 psi. Count the number of seconds between 25 psi and 20 psi. Repeat with "new" cap. The old one was nearly double the length of time to leak and the leak was barely audible. The "new" one was clearly hissing and dropped really fast. The old cap took 1/2 the time to fill to 25 psi.

Hurray for science!