Originally Posted by ryan51173

Mitsupartsman you are correct. I also noticed after taking a closer look the new ones have a bevel on both sides.

To update, I have succesfully change out the old rings and have installed the new ones. I found a procedure on how to do the 0-rings. The instructions I obtained are pretty good. They note that it's for changing the O-rings and not the heater core itself. The O-rings I purchased right from the dealer. P/N MR927776 which (accordingly to the dealer) supercedes P/N MR925655. They are $4.00 each in my neck of the woods. Several things to reccomend for the weekend warrior who decides to take this project on. TAKE YOUR TIME! I craked the plastic on the evaporater unit upon removal, whichI repaired w/ 2 part epoxy upon completion of the project. The big blunder that I have no problem admitting to, was that I didn't clean up any risidual coolant around the H/C. When you detach the pipes from the H/C to gain access to O-rings you have some coolant spill out. Well, I should have taken more time to dry that up.
I put most of the hardware back to test the O-rings and started the car. I noticed several drips, alot at first, the about 2 min later, a little drip. I figuredI wasn't getting offeasy and it was my H/C. So, off I want, removing parts from the driverside & dash to gain access to my H/C. After 1 hr. of removing parts and being extremely upset, I said to myself, maybe what you saw dripping was risdual coolant.I took a towel and cleaned up anything that resembled a drip on the floor. In went the key and the car ran for 20 min.. Low and behold no drips, hardly any coolant smell.So take the extra time to clean up the risdual coolant sorrounding the H/C. So, that added an extra 3hrs. removing and reinstalling parts to the driverside and the dash. I aslo, completly removed everything again.This allowed me tocompletely dried out the H/C and the H/C housing. I used 4 towels to soak up the coolant that was in the flr carpet. Well, I have to say I'm back in love w/ my Diamante.
Would like to note a couple of things to have. It helps to have alot of patience and be able to twist your body in positions you never thought you could be in.
Thanks for everyones help!

Originally Posted by Manybrews

you all wanna know what really works that DOESNT require any labor?

Go to GM.. buy a pack of their "coolant sealant" tabs. Drop 3 in your upper radiator hose.
BAM! it WILL stop the leak.

Im not a fan of band-aid type repairs, but this application is PERFECT for those tabs, and so far its worked on over 100 Diamantes without fail.

of course, fixing it correctly is a better way.. but not as quick and easy!

Originally Posted by Blck3G

wow I wouldnt even reccommend it...Not worth the Damage those things do....Just unplug the coolant passage @ the firewall and Plug it up both ends.

Originally Posted by darcymicro

I have already unhooked the lines to the core and joined them, so no heat. I would never put that stop leak in either, as it will clog the cooling system passages, particularly gunking up the radiator; I have seen this on another Diamante owner who used this, and when I removed the radiator cap, the gunk was clogging the top row, as it does not dissolve completely;It did not fix the leak in his and he took it to the dealer for repair, and the dealer voided his warrantee on the cooling system components after he used this; it is not a fix to the problem.
The fumes form ethylene glycol (coolant) are also toxic, and should never be breathed in.
If anyone has the procedure for replacing the o-rings I would appreciate the help.