Replacing o-rings for inlet/outlet heater pipes for Series I

Didn't take photos, but here is some info if one is has leaks around the two "heater pipes" that supply and return water to the LIM and water pump on a Series I and ultimately provide hot water to the heater core.

The setup on a Series I is quite different than the Series II.

You can see the pipes in the following diagram, labeled as parts 6 and 8.

These pipes mate to the engine and are sealed with o-rings, and the pipes are held in with a single 1/2" nut. They are then attached to two short sections of heater hose, which complete the circuit around the engine to the firewall and the heater.

Over time the o-rings on these pipes will harden and leak. I had a slow leak develop on the lower #6 pipe after I replaced the attached hoses. I think my moving them around while replacing the hoses caused the old ring on the #6 pipe to start a slow leak. That's not really a surprise after almost 20 years   

When I removed mine, the smaller o-ring was on pipe 8 was in relatively good shape and came off without any problem, but the ring on pipe 6 was completely flat and flush with its groove. When I tried to remove that ring, it disintegrated.

The GM part numbers for these o-rings are:

24500321 - which is part 4 in the diagram

24503160 - which is part 7 in the diagram

They are orange, which may be viton, but I'm not certain. When I bought the o-rings from my GM dealer, they cost about $2 each. GM wasn't able to provide the exact gauge or diameter, and I didn't measure them before installation. But they are different sizes.

Once one removes the single 1/2" nut from the bracket holding the pipes in place (and of course removed the hoses), the pipes should pull free from their holes with very little effort. And you do not have to remove any other components to remove the pipes and reinstall them. This is a very easy repair.

Once I had removed the old o-rings, I put a little grease on the ends of the pipes and the o-ring grooves, and the o-rings themselves. Then after wiping out their sockets, the pipes slid right back in with no effort.

I believe pipe 6 goes in first and pipe 8's bracket is the one on top of the stacked brackets, but check yours before you remove it to verify. The wear on the bracket should indicate which stacked first if you forget.

Then, just fill everything back up.

Remember the 95s use the traditional green coolant.

Yep. The 1995's are quite unique. I still like this system over the series II bypass system.

The 95s use the green coolant? Where'd you read that?

llamalor2112 wrote:

The 95s use the green coolant? Where'd you read that?

I was surprised to see that too.

My '94 Regal came with DexCool. I actually looked this up after seeing you say it for the first time and 94-95 is the timeframe when GM was making the change to Dex, so not all models got it right away. But I'm pretty sure Buick was all DexCool by '95.

Right, when I got mine it had a mix of dex/green which I flushed to straight dex. and of course after reading all the hundreds and hundreds of pages on dex v green, not at all worried about the dex. plastic lim gaskets such, end of story. haha

Well, coincidentally I just happen to have my 1995 Buick Riviera Owners Manual here with me (no I don't normally carry it around    ) ....

On page 7-41, Part D: Recommended Fluids and Lubricants

Quote :

Engine Coolant: 50/50 mixture of water (preferably distilled) and good quality ethlyene glycol base antifreeze (GM Part No. 1052753 or equivalent) conforming to GM Specification 1825M or approved recycled coolant confirming to GM Specification 1825M.

So what does that mean?   


There are lots of threads online about whether this means the "green" stuff or DexCool, but I can say that I don't have any DexCool stickers/instructions/references in the engine or in the manual. And when I got the car with 43k miles, it had the green stuff. GM apparently started to implement DexCool around 95, but other GM forums for 95 vintage cars (with the same owners manual entry) say that they used the "green stuff" from the factory.

But also reading online support forums, I think one would be fine using DexCool if you want though. I did read a service bulletin that strongly advised not to mix them though, and to be sure to fully flush the system before changing.

Maybe this will help.

Here is the info from the 1995 Buick Riviera Owners Manual

Here is the info from the 1996 Buick Riviera Owners Manual

Just whats been said. They were formulating and switching to dedicated dexcool use in 95. It had not been thrown into full-swing yet but by 96 was the officially backed in-house substance. It's not necessary to use one over the other, Dex is simply what GM officially endorses use of. If the 95 model riv had debuted in 96, it would've had the dex-backing too.

Yep, no religion here   

Alright. Successfully raised a mountain out of a molehill and successfully repelled back down   my deed of confusion for the day is done

Very interesting info, thanks.

I have heard not to mix the two - eventually the mix will turn to mud, which happened to my '94. It had dex-cool labels all over it, I'm guessing somebody put the green stuff in without a full flush. Or it could have just been really old dex...

My riv had a mix going on when I bought it. Quick end to that. Looking at the flush of the dex I put in two winters ago with the new rad I'd say everything is good. Looks nice and clean to me in this super extra dorky vid I made upon discovering that my phone could capture slow-mo while I was waiting for the rad to drain haha

http://magis.to/JC4vWg1OFgR6f3sPYnZLAHs