2001 Volvo 2.3 T5 Overheating - diagnosis confirmation pls

[dern]

Hi,

I've had my 2001 2.3 T5 for a year and a half and have put about 15k miles on it. Car has done 120k miles.

This evening on the way to work I noticed that the temp gauge was a little over the half way mark and this is very unusual as it's normally just below the half way mark. Pulled in to our village and started to climb the hill and the temperature gauge started to climb to about 3/4 at which point I stopped.

The expansion tank is completely full of water, the fan is running and the top hose is hot.

Let it cool down and drove it home and the temperature gauge hovered a little above half way but I was babying it.

Started to check stuff over.

The expansion tank seems to be holding pressure even when completely full. Cracking the expansion tank open caused coolant to pour out. So I don't think it's the cap.

If I refill the system and disconnect the top hose to the thermostat and run the engine I can see water being pumped out so believe the pump is ok (don't worry, didn't do it for long).

I've not been able to get the thermostat out yet so haven't tested that.

There are no external leaks at all.

The fan was running when I pulled over when the car was overheating and it did feel pretty hot so believe the sensor is probably ok and the fan is ok.

If I refill with water and run the engine it's all calm and then at some point (presumably when the thermostat opens?) it start pumping water out of the expansion tank top at a rate of knots. This sort of suggests that the thermostat is working I guess.

There's no oil in the water and no water in the oil.

There's no steam coming out of the exhaust.

Based on all of that do you think that a headgasket failure between the combustion chamber(s) and the cooling channels is the most likely culprit?

If so, given that I didn't let it overheat should I crack on, get the head off, measure the head for straightness, fit a new gasket and rebuild or is there something else I need to check or something else I've forgotten to check?

Thanks,

Mark

Edited by dern on Tuesday 24th April 19:41

[Steve_D]

I would replace the stat and the pressure cap before breaking it down.
I don't believe you have yet eliminated the stat.

Steve

[dern]

Steve_D said:

I would replace the stat and the pressure cap before breaking it down.
I don't believe you have yet eliminated the stat.

You're absolutely right. I've ordered those bits and will fit them at the weekend.

Regards,

Mark

[morgrp]

Steve_D said:

I would replace the stat and the pressure cap before breaking it down.
I don't believe you have yet eliminated the stat.

Steve

Very sound advice - will more than likely be one of the two - most likely stat is sticking - but as both are so cheap to replace I would do both - a knackered expansion cap will cause boiling in the head as it effectively stops the system being pressurised - a potentially serious prOblem - don't over tighten the cap either - just nip it up nicely - I've done both on my t5 and cured my fluctuating temp gauge

[martycossie]

check the return pipe to header tank may be blocket

[dern]

martycossie said:

check the return pipe to header tank may be blocket

Ok, will do.

Thanks,

Mark

[BlackBeastT5]

And change the temp sensor while your at it (just underneath the thermostat). Use genuine Volvo coolant.

[dern]

Hi all.

On further investigation I stuck the thermostat in a pad alongside the new one. The new one opens up at 90 ish and the old one never opens even when the water is boiling so that was the issue.

Changed the thermostat and the expansion cap (as a safety measure), flushed and refilled with 50/50 again and it seems happy. Watched the temp through the obd port and you can see the thermostat opening and the fans working and all looks good.

Thanks,

Mark