I am in the process of rebuilding my 1989 3.0 Montero. I have the new heads, head set, head bolts, and timing belt. On beginning the re-install I went to replace the o-ring on the tube the leads from the heater core to the rear of the water pump and goes under the intake manifold. The one that comes with the head set is a normal round o-ring. The one I took out is more squared off and fits tightly whereas the aftermarket one fits way too loose. I then went to the Mits Dealer and looked it up and it showed the same one. No way am I going to put this together and have to pull the whole engine back apart just to fix this o-ring again. Has anyone had this problem and know the proper part #? Maybe someone has replaced it with a squared off oring and I will have to check the local aftermarket. PLEASE HELP!

I've read here that many of the rebuild and waterpump kits (even those from MMC) have had the wrong o-ring. I'd suggest going to the dealer and ordering the one that the parts manual shows and see if it's correct. The number is MD030763 and it's a 15.9 size.

[EDIT] Wait a minute - I just read your question again. It's likely that the o-ring looks squared off because it swelled up against the walls of the waterpump and "became" squared off over time. If the supplied o-ring is a snug fit, use it. [EDIT]

Frank

Frank

I wish it was. The supplied Oring and the one from the dealer arent tight enough. I suspect that the hole has become enlarged over time. I can put the pipe in and out of the hole very easily, with no resistance at all. If nothing else I will have to pack it with silicone and find the largest Oring I can out the Oring assortment kit.

doing all that work and not replacing the water pump? napa sells a good one for under $50 bucks, $43 if memeory serves & i put the p/n in the repository. i got one when i did my head job, the o-ring that came with it fit perfectly <img src="/forums/images/graemlins/kewl.gif" alt="" />. the one that came with my gasket kit for the head job was a sloppy fit aswell, so it went straight into the rubbish.

I just got one from the Mitsubishi dealer.
It is round.

Well, I went through the gasket assortment and found one that fits pretty well. Not replacing the water pump because it was just replaced less then 8 months ago by previous owner. They replaced the timing belt too but I just dont feel comfortable reusing it so I got a new one. Putting the new heads on tomorrow morning. Cant wait to get it back on the road. I have my LT285/75r16 Firestone Destination MTs sitting there waiting to be installed. Im just going to wait to make sure everything is running ok to put on the tires because if not, the Montero is going to the junkyard and the tires will be resold as new.

So how big is it? I need to get one is why.

TIA,

Ray <img src="/forums/images/graemlins/kewl.gif" alt="" />