Volvo S80 Cooling system bubbling?

Post by **johnmblignaut** » 21 Nov 2011, 22:51

I have a 2000 model S80 ... Just recently, it has begun to make bubbling sounds in the cooling system. I say bubbling since I don't know if it is boiling because the temperature gauge on the cluster shows just below half... I have noticed that the cooling system is dumping fluid once the car is parked for a few minutes.... probably from the expansion chamber?? ... Could the expansion chamber cap be faulty?......Could I have a blown gasket?? ( no discoloration of the oil, or loss of power ).. or is the gauge not registering correctly thus causing the fan not to kick in?... Is there a relay on the system that could be faulty?..... I took the car for a electronic diagnostic check at the Bosch service station and they idled it for ages and found no fault? . They changed the thermostat but the problem continues.. Could the Fan be kicking in intermittently?... I look forward to your diagnosis...

retcoastie · Post by **retcoastie** » 22 Nov 2011, 09:08

If you have bubbles soon after starting the cold car, do a compression check to diagnose the head/ head gasket.

If the bubbles appear after driving, especially in town, check to see that the electric radiator fan is working. You can check this by starting the car and letting it idle until the bubbles start. If the fan has not come on by then and the water hoses are hot, the fan is a likely culprit. The problem is that a lot of things control the fan. I could not come up with a diagram. I added a manual switch so that my grandson can turn the fan on whenever he gets in a situation where there is not enough ram air coming thru the radiator. You should be able to hear that fan, listen closely.

Good luck, lets us know what you find....

Post by **johnmblignaut** » 23 Nov 2011, 07:28

Hi retcoastie..... many thanx, I will try your advice and report my findings..... johmblignaut

Post by **boosted5cyl** » 23 Nov 2011, 09:23

Unless its bubbling while its still cold, skip the compression check and put a new expansion tank cap on it. They are pretty cheap. If the symptoms persist then persue a path of checking for headgasket issues.
Fan or thermostat issues (stuck closed) will cause the temp gauge to creep past the halfway mark, unless your temp sensor is having issues. Anyway, start with the simple thing that you already thought of: change the expansion tank cap.

Post by **Brucebo** » 23 Nov 2011, 10:20

Is your thermostat good. It's not stuck shut is is?

-B

Post by **johnmblignaut** » 23 Nov 2011, 21:22

Hi Brucebo..... The thermostat is the first thing that the guys at Bosch thought may be the problem.... it was replaced but the problem persistes

Post by **johnmblignaut** » 23 Nov 2011, 21:28

Hi Boosted 5cyl...... thanx, I will start with the expansion tank since you are right, the cooling system only starts bubbling after driving for about 5 miles.... the cooling fluid escapes from the overflow or overpressure line just below the expansion tank cap....So the cap could be the culprit...

retcoastie · Post by **retcoastie** » 25 Nov 2011, 21:21

John,

I think you are chasing a result, not a cause, at the expansion tank. You have to think, what is causing the bubbles? Where are they coming from? Granted the fluid is escaping from the tank, but the bubbles did not start there.

When the bubbles start after five miles of driving and fluid is escaping from the tank, is the fan running?????? The bubbles are starting inside the engine, because the coolant is too hot. Why? Either because the coolant is not being circulated out of the engine fast enough and is overheating (low flow), or the coolant that is circulated out of the engine is not being cooled enough and is returned to the engine too hot (low air flow thru radiator).

When the coolant is not circulating the first thing to check is the thermostat (already replaced), then the radiator being clogged, followed by the water pump and lastly a blockage in one of the engine passages or a hose. In any case, the car should sense the excess heat and turn the fan on in an attempt to cool the coolant.

When the coolant is not being cooled adequately the first thing to check is the fan running properly and, if it is, is enough air actually being pulled thru the radiator?

The deciding factor in either case is the fan, running or not.

Good luck and inquiring minds want to know what you find.

Post by **boosted5cyl** » 26 Nov 2011, 20:30

Retcoastie, you do have a point however I think you are overlooking the importance and role of maintining correct pressure in the cooling system.
The cooling system is intended to operate under pressure of as much as 18PSI the intent of which is to significantly raise the boiling point of the coolant\fluid. Failure to hold pressure will result in premature boiling of the cooling fluid, leading to "bubbles". This often throws a curveball for inexperienced mechanics. Many times, when the pressure is being lost there will be no evidence of overheating on the temperature gauge as the actual temperature of the fluid will not get that high before boiling off. In some systems if the pressure is not maintained adequately, the fluid can even boil before the thermostat opening temperature is reached and/or before the fan kicks in.

Replacing the cap is a cheap, easy and in my opinion essential starting point with an older car. A cap that doesn't hold pressure is very often a cause of the symptoms that the OP describes.

jasonconway5 · Post by **jasonconway5** » 06 Jul 2012, 18:38

Its been awhile, what did you find? I was gonna suggest head gasket or cracked head. Im having the same problem, but I also have a random missfire. no smoke or external fluid leaks and no water in oil but losing a little water along with bubbling in resevior while running and after shut off. about to pull the plugs now and look for green tint.