2001 s80 Pressure in coolant only when in traffic

maven05 · Post by **maven05** » 26 Aug 2013, 09:51

I've read this forum and many others but could not find a solution to my problem.
If any Volvo mechanics who might of seen or came across this problem could help that would be awesome.
Problem: Pressure builds up in the coolant system when I drive in hot weather mainly when driving from traffic light to traffic light (or in traffic).
How I know it: I get message that Coolant is low on the dashboard. I let some air out by slightly opening the cap.
What I did: Changed thermostat and engine coolant sensor, changed fan also (it was used fan but in working condition).
I drove about 400km on the straight road (drove to another city) and had no problems at all with pressure.
I think i get pressure in the coolant because the fan doesn't turn on when it should. Even in hot weather when i turn off the engine and it is HOT the fan does not turn on. The interesting part is when I unplug the engine temperature sensor the fan starts to rotate and the temperature gauge drops on the dashboard. When I see the board computer to reset itself and the temperature gauge goes to the middle the fan stops working and few minutes later I get a message that the coolant low because of the pressure.
Almost every mechanic I talked to in Tallinn (Estonia) told me that I have blown head gasket but would not my hoses explode when I drove 400km because there would be constant pressure?

I really want to figure out what is the problem here.
Any help would be greatly appreciated.

Max

fn42 · Post by **fn42** » 26 Aug 2013, 11:19

could be a head gasket, but I'm wondering if it's the water pump? Have you tried dropping it in neutral and holding the engine at ~2k rpm while stopped in traffic to see how it behaves?

maven05 · Post by **maven05** » 26 Aug 2013, 12:48

Thank you for your response!

No, I haven't tried that. Didn't even think that it could be the water pump because it was replaced in November 2012 (15K km ago). But I will try that tomorrow and let you know what happens. Btw, what might happen?

fn42 · Post by **fn42** » 26 Aug 2013, 13:19

you should hear the fan kicking in and the coolant should stop boiling out. if the water pump can't circulate coolant fast enough the coolant could start boiling out while the coolant temp sensor still reads good temps.

You can also try just turning the heat on too while it's stuck in traffic. No heat is another indication that there is low/no coolant circulation

maven05 · Post by **maven05** » 26 Aug 2013, 13:25

I get LOTS of heat. Just tried it today when it was about 29C out i was steaming inside (turned the heat on for few minutes just to check).

I also checked the Engine temp. Sensor with multimeter and it read temperature fine and works as it should.

maven05 · Post by **maven05** » 27 Aug 2013, 11:13

Went to day to a friend of mine who works at TOYOTA center.
He ran a simple coolant test and the liquid changed the color.
Will drive to the shop tomorrow and change the gasket. Hope that it will take just a day to change it.
Will keep you updated on this issue.

maven05 · Post by **maven05** » 31 Aug 2013, 10:34

Just got my car back from the shop.
The gasket was changed. Drove around for a while in traffic and on the clear road. No sign of pressure or anything like I had before.
Seems like everything is fixed for now.
This issue is fixed and I'm very happy! =)