Hi guys, I'm not sure if i'm completely off my rocker here, but I've visited this forum a few times in the past and found very helpful information so I thought I'd reach out and see if anyone has had a similar issue.

I've got an '87 GT that I have recently purchased. It's been driven very, very sparsely over the last 15 years or so in that it only has 49k miles on it. I recently went to swap the thermostat as the old one was sticking, but when I went to replace the cap, I could not get it on without a herculean effort. Upon closer inspection, I realized that the thermostat itself sticks out of the housing by a small amount. I measured the new thermostat against the old one and even bought a second one to make sure, but they are all the same size. The housing itself appears to be stock so I'm confused about what could be the issue here. If I remove the thermostat the cap fits fine.

Any ideas?

Apply some grease to the rubber seal of the thermostat before installing. The thermostat needs to snap down into position. Don't force it though. There might be some corrosion in the groove it's supposed to pop into. If it's bad, clean it up with some emery cloth. (Try not to let any crud get in the coolant.)

[This message has been edited by Patrick (edited 01-02-2021).]

quote Originally posted by Patrick: Apply some grease to the rubber seal of the thermostat before installing. The thermostat needs to snap down into position. Don't force it though. There might be some corrosion in the groove it's supposed to pop into. If it's bad, clean it up with some emery cloth. (Try not to let any crud get in the coolant.)

Thanks! I had no idea that it was supposed to snap into place. That might be the whole issue. I'll try a bit of grease and see how it goes.