Cooling system pressurized

Help, Advice, Owners' Discussion and DIY Tutorials on the Volvo S80 model. Sometimes called an "executive car", the S80 was and continues to be Volvo's top-of-the-line passenger car.
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thienle
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Cooling system pressurized

Post by thienle »

Hello,

I have a 2001, S80 2.9L. There are a lot of pressure in the cooling system when the overflow tank cap closed tight. When the cap is tightly closed. I'll get a "low cooling level message", when checked there is no cooling level in the overflow tank and I noticed that there are leakage coming from where the hose connecting to the radiator due to too much pressure in the cooling system. The moment that I cracked opened the overflow tank cap to release the pressure, the coolant instantaneously over flow the over flow tank.

I currently operate the car with the cap loose to release the pressure. I heard that there is a pressure release device inside the cap that release the pressure to prevent the cooling system from pressurize?....not sure where is it releasing to? On other car it released to the atmosphere. I've a new cap on the overflow tank but it doesn't help. Thank you very much for the help.

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June
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Post by June »

The cap could be bad. The cap is to regulate pressure no higher than the set pressure indicated on the cap. Replace the cap and see what that does. For Volvo there is a green cap our S80 came from the factory with, and a black cap that holds 1/2the pressure that is the correct cap for a 1990 240. The last several cars I bought a new black cap and installed it before driving off the lot. My 2004 S80 T6 is pushing 170K with no I'll effects from running 1/2 pressure in the cooling system. One benefit, no leaking or blown heater core so far. Whichever cap you buy, a new one should release pressure if it exceeds the cap rating. June

Oh don't go cheap here, buy a Genuine Volvo cap only!
My Volvo cars owned
1989 740 GLT ordered
1994 850 4door standard shift ordered
1996 960 ordered
1998 S90 ordered totalled after 3 weeks
1998 V70 GT dealer stock car
2002 S80 T6 ordered totalled
2004 S80 T6 dealer stock car and current car owned

thienle
Posts: 27
Joined: Fri Jul 31, 2009 2:47 pm
Year and Model: S80 2001 nonturbo
Location: Boston
Has thanked: 4 times

Post by thienle »

Thanks June. I did purchase new cap but the pressure still exist.

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SuperHerman
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Post by SuperHerman »

Sounds like you have either a bad thermostat or a blown head gasket. Maybe a failed water pump.

You can try installing a new thermostat. What does the hose running to it feel like? Hot? Does it feel like coolant is flowing through it?

How does your oil look? Can you pull the spark plugs and look at them and the piston tops to look for signs of coolant cleaning.

What happens when you turn the heater on full?

Those are the low lying fruit to check first. Report back and we can work through more checks.

thienle
Posts: 27
Joined: Fri Jul 31, 2009 2:47 pm
Year and Model: S80 2001 nonturbo
Location: Boston
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Post by thienle »

Thank you SuperHerman.

I hoped that it is a bad thermostat but not a blown head gasket. Got new thermostat. Still waiting for thermostat housing gasket. Will install it probably this coming up weekend. Any advise and/or link to how to replace the thermostat is greatly appreciated.

The radiator hoses are running hot...I guess that it should be? My best guess is the coolant flowing through it. The thermometer is at 50% marked.

The oil appear to be normal. Will probably follow your recommendations and remove the spark plug this weekend to look for signs of coolant.

The heater appear to be normal on full.....hot air coming out from the vents

Will provide more updates when I have a chance to replace the thermostat this coming weekend.

Thank you very much again.

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June
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Post by June »

If you suspect the head gasket, than use combustion gas test test tool. It's easy to do and no pulling spark plugs, just have to open the coolant cap. June
My Volvo cars owned
1989 740 GLT ordered
1994 850 4door standard shift ordered
1996 960 ordered
1998 S90 ordered totalled after 3 weeks
1998 V70 GT dealer stock car
2002 S80 T6 ordered totalled
2004 S80 T6 dealer stock car and current car owned

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SuperHerman
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Post by SuperHerman »

There should be write ups on it. On the 2.9 it can be tricky. Many have broken the plastic coolant nipple on the thermostat. I do not recall if it matters if you change the entire assembly.

If you are not, be careful of that plastic nipple sticking out the timing cover that connects to the overflow tank. I would disconnect the coolant bottle end and then the thermostat end. It is a squeeze push/pull fitting. Tough as it is hard to get there. Some leave it on the thermostat side and then gently work the plastic cover off. Just work slowly and repeatedly so you do not stress that joint. Many have broken theirs. I got mine off fine only to break it in reinstall. There are fixes but that is another story.

While you are in there carefully check your water pump. Be creative. Maybe try turning the engine over to make sure pump impeller is intact. You may need a helper and it could make a mess. Like I said, be creative. Explore fully what you can when the thermostat is out. Check the pump bearing visually under the restrictions of space and timing belt. You have it opened up so look. I had an Audi where the pump shaft sheared off and the belt would spin but the impeller would not.

thienle
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Post by thienle »

Still waiting for the thermostat housing gasket. I did pull all 6 spark plugs and used a borescope to inspection the top of the piston. All six appear to be normal with no coolant/liquid.

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SuperHerman
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Post by SuperHerman »

You are not looking for coolant or liquid. You are looking for clean piston tops or areas. They all should look fairly and equally dirty.

Sometimes with blown head gaskets the coolant seeps in and steam cleans where the breach is leaving areas that are inconsistently clean compared to the rest of the piston tops. Not definitive but a solid clue that is visually easily discernible.

thienle
Posts: 27
Joined: Fri Jul 31, 2009 2:47 pm
Year and Model: S80 2001 nonturbo
Location: Boston
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Post by thienle »

If that the case then I might have a blown head gasket. The top of the pistons are not uniformly dirty. Some area is cleaner than others. I took a few photos of the top of the piston but don't know how to attached to the post. Any instruction on how to replace the head gasket or a diagram of the "explore view" of the engine is greatly appreciate.

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