I just replaced my radiator last weekend with a Visteon HD cooling radiator from Advance Auto Parts. The core is twice as thick as my original. The installation seemed straight forward. The trans cooling lines are flare type. The engine cooler lines , I didn't notice anything unusual so I just screwed them back in. Well, I ended up with 4 leaks at all the lines!
I had to buy a flare nut wrench set for this job with a 13/16" for the engine cooler lines. All lines are very snug. Yesterday, I was examining the old radiator and noticed that the left side (engine cooler fittings) , are not flare and that there was some type of rubber seal left in one of the holes, a blue rubber seal of some type. Are these special seals for these lines ?? What I'm going to do is try some o-rings on the engine cooler side. On the trans cooler side, not really sure what to do, but was also thinking of some thin o-rings behind the flare.

Anyone have any knowledge of what seals to use on the engine cooling lines or suggestions to get the flares to seal ???

Thanks.

The new radatior could be bad and some new parts can be defective.What year?The transmission lines have no o ring and the oil lines do.

You don't say what year and engine you have.

On my '98 K2500 7.4 the oil cooler lines on the drivers side definitely have o-rings. Not sure about the tranny lines on the pass side.

I just replaced my radiator last weekend with a Visteon HD cooling radiator from Advance Auto Parts. The core is twice as thick as my original. The installation seemed straight forward. The trans cooling lines are flare type. The engine cooler lines , I didn't notice anything unusual so I just screwed them back in. Well, I ended up with 4 leaks at all the lines!
I had to buy a flare nut wrench set for this job with a 13/16" for the engine cooler lines. All lines are very snug. Yesterday, I was examining the old radiator and noticed that the left side (engine cooler fittings) , are not flare and that there was some type of rubber seal left in one of the holes, a blue rubber seal of some type. Are these special seals for these lines ?? What I'm going to do is try some o-rings on the engine cooler side. On the trans cooler side, not really sure what to do, but was also thinking of some thin o-rings behind the flare.
Anyone have any knowledge of what seals to use on the engine cooling lines or suggestions to get the flares to seal ???

Thanks.


this is typical when the radiator does not conform to the GM fluid lines ...your problem is very common..most GM vehicles built from the 1990's use rubber seals instead of the old style that was a flare...

" C " clips lock in the rubber sealed termination of the line into the radiator..

Most likely you have oil ring seals unless the flare is type AN 45 degree. You need to make sure there is no debris on the either of the flare ends before you install new o-rings. You should be able to get the o-rings at any local auto parts store. Just make sure they are resistant to ATF fluid. They should be, but better safe than sorry - so just ask.

The Tahoe is a 1998. After further examination, I found a blue rubber seal stuck in the old engine cooler side of the radiator. It looks kind of like a cone seal, but not sure. I looked at the brass adapters that came with(not for my application. They had o-rings on the bottom of them. I peeled them off the adapters and used them on my oil lines. They seem to be good now. I never bothered to check that side, I had just assumed both sides were flare.

On the tranny side, the flares on the lines were clean, as were the raised "flare ridge" in the new radiator. I didn't really know what to do there. My solution was to find some very thin o-rings and slip them behind the flare. I also used some teflon tape over the threads. Seems to have worked.