98 v70 GLT expanding coolant

Post by **stephansvolvo** » 17 Oct 2019, 19:34

a few months ago, i was sitting at idle and suddenly steam started rolling from under the hood. I opened it and found coolant pushing out from under the expansion tank. No over heating although the coolant temp gauge did notch up a few lines.
I replaced the cap with a new one. Added more fluid and I have been driving it with it. I have not had it do that again until tonight.
I daily drive fairly short distances and do not idle. Tonight I drove to Portland, 2.5 hours, and as soon as I got off the highway and hit a red light the temp gauge went up a couple of notches and I saw steam. Did not over heat according to the gauge.
I replaced the head and all that Jazz five years ago.
I changed my oil 3 months ago and I didn’t notice any coolant in it. I have not tested the coolant, yet.

Any Thoughts?

Thanks
Stephan

Post by **bmdubya1198** » 17 Oct 2019, 21:05

How old if your thermostat? That may have failed and blocked coolant flow. If you've ruled out any blockages, it would be smart to either do a leakdown test or test for exhaust gases in the coolant. You can rent or buy a kit from Auto Zone to test for exhaust. I'd start with that test, it's very easy.
Ideally, you'll find a blockage and you don't have any head gasket issues.

Post by **stephansvolvo** » 18 Oct 2019, 16:24

bmdubya1198 wrote: ↑17 Oct 2019, 21:05 How old if your thermostat? That may have failed and blocked coolant flow. If you've ruled out any blockages, it would be smart to either do a leakdown test or test for exhaust gases in the coolant. You can rent or buy a kit from Auto Zone to test for exhaust. I'd start with that test, it's very easy.
Ideally, you'll find a blockage and you don't have any head gasket issues.

Tstat is 4.5 years old. I purchased a new one and will install it this weekend. I might as well do the coolant test too. While I’m in there.

Post by **bmdubya1198** » 18 Oct 2019, 21:01

Good deal, let us know how it goes.

Post by **ZionXIX** » 18 Oct 2019, 21:09

Mine was doing exactly the same thing. My fan was not engaging unless the A/C was running. It turned out to be a bad temp sensor. Replaced it and all went back to normal. I tried the thermostat first and then the fan relay. I had a bluetooth obd II reader showing normal temps the entire time. My temp sensor was reporting false numbers to the ecu. The easy thing is to start the car with hood open and the A/C off. Watch as the coolant expands and see if the fan comes on. The fan should activate well before the coolant reaches the tops. If it doesnt kick on try turn the A/C on, if the fan works then you may have a bad temp sensor or a corroded plug. Just my experience.

Post by **bmdubya1198** » 19 Oct 2019, 08:11

I was going to mention that too, make sure your fan is running. There are a couple reasons that will stop, the ECT sensor, the relay, and the fan itself all being possibilities.