Volvo AWD 850 Forum

INDEX FOR 10/2025(CURRENT) INDEX FOR 7/2017 850 INDEX

[<<]  [>>]


THREADED THREADED EXPANDED FLAT PRINT ALL
MESSAGES IN THIS THREAD




  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

I have about 140K on my 850. For the past year it has been using more and more coolant about a pint a week. No coolant leaks could be found. Recently the coolant reservoir seemed to overpressurize with coolant spraying out of the hose connection at the bottom of the reservoir with no apparent problem with the hose. I assumed the head gasket had been leaking for some time and just got worse so I replaced the head gasket but the problem continues. According to the temperture gauge the engine is not overheating but will overpressurize even when just idling. I've noticed that the fan does not come on when this is happening but according to the temp gauge it reads right in the middle of the gauge and may not be calling for the fan to start. I'm wondering if it is very likely the engine is overheating at idle causing the coolant reservoir to overpressurize and a temp gauge reading in the mid range(faulty). Thanks for any thoughts.








  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

Getting a new cap is a good, cheap idea and worth pursuing.

What kind of thermostat are you using? OE works best. Does the upper radiator hose get hot, indicating that the thermostat is opening? Has the ECT sensor been changed?

I would just replace the small overflow hose at the bottom of the coolant tank, and inspect the plastic nipple of the tank closely for a crack. The plastic parts do not last forever.
--
My back feels better when I sit in a Volvo seat








  REPLY TO THIS MESSAGE    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

I did replace the ECT. The thermostat is after market but the upper hose does get hot. I will try a different cap but I don't see how the cap would make a difference. Thanks much








  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

The cap is designed to release excess pressure. If the hole gets plugged...
Besides, if the cap is original, it has lived past its life.
--
My back feels better when I sit in a Volvo seat








  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

Klaus, You were right again. I found small cracks in the bottom of the tank where the lowere hose connects. Replaced the tank, hose and cap and problem solved, although I assume I originally had two problems, the tank and the head gasket. When this started happening I idled the car in my garage to see what would happen. With the cap off after the car warmed up there were many bubbles coming up in the coolant tank. Eventually the tank would overflow with all these bubbles. I assumed this meant the head gasket was leaking badly. However on Matthews Volvo site I was reading that someone said the way this cooling system is designed the coolant will boil in the engine at idle if the cap is off due to the low pressure on the coolant. So it made me wonder if what I was seeing was just normal behavior of the system and not a bad head gasket. Thoughts? Thanks again for the great help. PS This is my wife's car I've parked my 1995 850 wagon that was running great in favor of a 1999.5 VW Jetta TDI. I couldn't resist the 50mpg.








  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

"Matthews" is correct about the antifreeze boiling with the cap off. For around $20 you can get an IR temperature gauge and point it at the thermometer housing and check the heat. Cute little tool!

If there are bubbles with the cap on and system pressurized, then you have a problem. You will also notice a fluid level drop because the pressure in the system will force the coolant past a bad head gasket once the engine is shut off.

I suggest using a sharpie and mark the level of antifreeze in the tank and check it for a while. If you think it is going down, get a compression test and/or pull all of the spark plugs and inspect the combustion chambers for one that is very clean.

Keep that 1995 running!

Regarding the diesel, you will find that the carbon deposits in the intake manifold will restrict air flow after 100K or so. It is a bear to clean out. But it is nice to not have spark plugs. Make sure you do not get #2 diesel when the temps get to 10F or less, as the fuel will gel. I had a full tank go solid at -10F.
--
My back feels better when I sit in a Volvo seat








  REPLY TO THIS MESSAGE    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

Is the 'radiator' cap bad ?

Greg








  REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

Over pressurized coolant reservoir 850 1995

I was just going to suggest that as well. Perhaps grab a cap from a different car and see what happens...







<< < > >>



©Jarrod Stenberg 1997-2022. All material except where indicated.


All participants agree to these terms.

Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.