I replaced the thermostat in my 1999 V70. Antifreeze is leaking by. I used the correct thermostat and gasket. Should I use some sort of additional gasket material to prevent this. I do not want to tighten the bolts down tighter and break them off. Thanks

You're going to end up pulling this apart again I'm afraid...

I think this is supposed to seal up with just the rubber gasket thing on the thermostat.

With that said though, I always found I was looking for a bit more insurance that it wasn't going to leak. You need to make sure the mounting surfaces of the upper and lower thermostat housing are very clean and free of nicks. It's soft metal and marks up easy. A little sandpaper might clear up some of the nicks if there are some, but it will make the seal all that much worse against the other half...

Last time I did this job I used a smear of sensor safe silicone on both housings, being careful not to get any 'inside' where it would end up in the coolant. Let it dry for about 10 minutes applied to each half before reassembling. If you've got the time it would be good to assemble the two halves and just go finger-tight on the bolts, and leave it overnight before refilling with coolant. The next day torque the bolts down and then fill the system back up. The finger-tight start pushes the silicone into all the cracks/etc but doesn't squish it all out. The waiting time gives the silicone a chance to set up in the gap so that when you torque it together it acts more like a gasket. You seriously only need a smear, not a 'bead'. There should be very little if anything squish out when you tighten the bolts down. It should basically still be transparent - you want it on there that thin.

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1998 V70 AWD->FWD Turbo 200k+

I clearly see the error that I made now that you describe the proper procedure. It is no problem taking it back apart and correcting it. By the way do you know the torque value for the two bolts. I am going to pick up a torque wrench the time is long overdue for that.

Thanks

There is no 'gasket' but just a sealing ring on the thermostat itself. You will need to lower the coolant level again, take the cover off and find out why the sealing ring is not working properly.

Is this an OEM thermostat or a knockoff? Beware of cheap imitations, they tend to fail in the closed mode rather than open, which can overheat an engine faster than you can say boo.

Klaus
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Always willing to listen, just not able to take direction.

I admit that I got the part at the local NAPA store. The gasket that came with the thermostat did appear to be thinner but I figured that the original gasket swelled a bit over time. I will go to volvo and get the proper part.

Thanks

If you go to the dealer, ask for new 10mm bolts for the housing instead of the Torx screws.

I didn't torque mine down, just snug.

Klaus
--
Always willing to listen, just not able to take direction.

make sure you place the gasket over/around the flange of the thermostat itself so it sits both on top and on the bottom surrounding the flange, sorry if this is stating the obvious but it's the first one Ive seen set up this way .