I have the engine in still in some state of disassembly after replacing the head gasket, and am putting things back together. In re-fitting the thermostat case (part 9) back onto the connecting pipe (part 12) in the following diagram, should I necessarily need to replace this o-ring (part 19)? It looks okay and hasn't been a problem before the disconnection of the case and the pipe, and would be at least a week of waiting to obtain a new one. I suppose perhaps ideally it would be best to go ahead and replace it but what I'm wondering is whether chances are still good it will seal just fine again without replacement, or should this o-ring definitely be replaced after this disconnection because if re-used will almost certainly not seal anymore? Any comments appreciated.

 

Personally I would reuse it. As long as its not hard and brittle it should be fine. And no sense waiting all that time for that part. Put it back together and if it leaks then order a new one.

 

Great. Just what I was hoping to hear. Re-use it I will. Thanks for the input.

 

agree with live2, throw some grease on it and use it

 

Aww. Already put the parts together and got it bolted in and everything now. Gotta put grease on it?

 

No. If it leaks, get a new o-ring.

 

Okay. Thanks for the replies. I won't worry about it. IF it leaks, I'll get a new one then. Probably generally a good idea to put a little grease or maybe vaseline or something on a new o-ring?

 

A little grease or something would be good. I'd use something heavier than vaseline, but that's just because I've got several kinds of grease around the garage.

Not worth it to remove that just for grease. If it leaks, get a new O-ring and use a bit of grease this time.

 

Got it. Thanks Jim.