1996 Volvo 855 Leak at heater hose coupling

banjoman · Post by **banjoman** » 01 Jun 2015, 08:49

I installed a new heater core, coupling, O-rings, pipes, and hoses about three months ago. I used the best quality parts available and was careful to install the O-rings in the correct sequence. I just discovered I have a leak inside the car at the lower coupling. I have tried pushing hard on the pipe into the coupling but it does not help. I am aware of the bypass idea to get rid of the coupling but am not ready to do that. Any ideas on how to stop the leak?

Post by **cn90** » 01 Jun 2015, 09:50

@banjo,

Are you using aftermarket O-rings? They are notorious for leaking.

Dealer O-rings are much better.

Anyway, I am glad I did the coupler bypass, nothing to worry about. So far so good (I wrote the bypass DIY in forum).

banjoman · Post by **banjoman** » 01 Jun 2015, 09:56

I got a Volvo o-ring and coupler from fcp. How long have you had the bypass?

Post by **cn90** » 01 Jun 2015, 11:00

To me the firewall coupler is bad design, this is why I got rid of it at 167K miles.

Detail below...

https://www.matthewsvolvosite.com/forums ... hp?t=69238

jonesboy1983 · Post by **jonesboy1983** » 01 Jun 2015, 11:10

When I replaced the coupler, it had all the o-rings etc. attached inside already. All that was required was to plug the heather hoses into the new coupler. Perhaps your removed the o-rings and plastic spacers from the coupling and that damaged them now causing the leak? Just an idea.

banjoman · Post by **banjoman** » 01 Jun 2015, 13:45

The coupler are Volvo and I think the rings came separately and had to be inserted. The leak happens only after you run the car for a while, and then it is a small stream from the lower coupler down the firewall, not huge but enough to require correction.

jonesboy1983 · Post by **jonesboy1983** » 01 Jun 2015, 14:02

I think that is the problem though. The coupler I got from Volvo did not require adding any additional rings. All you had to do was plug in the heater hoses from one end and the pipes from the other. I remember because I bought the plastic plugs and rings separately and returned them because I never used them when I replaced my heater hoses and heater core.

Post by **precopster** » 01 Jun 2015, 15:25

The "I inserted the o rings in the correct sequence" statement also has me worried. You should just simply push in the hoses with a new coupler; nothing more to do.

Was it in a sealed bag?

In case you want to re-assemble the o rings it's rubber-plastic-rubber-plastic-rubber starting from the deepest point.

banjoman · Post by **banjoman** » 03 Jun 2015, 08:15

I first ordered just the rings/spacers and inserted those in the old coupler; when that leaked, I ordered a new coupler (all Volvo parts). When I say I inserted the rings/spacers in the correct sequence, I may be thinking of the first failed attempt, and it is probable that I did not bother the rings/spacers in the new coupler and just inserted the metal pipes. The little leak continues. I just loosened the screw holding the metal pipes to the core so I could perhaps push lower pipe further into the coupler; drove it for about 15 minutes, and the little dribble was there.

banjoman · Post by **banjoman** » 04 Jun 2015, 14:33

To close this, I removed the coupler and found a broken o-ring. The ring was new when installed three months ago. I noticed the plastic spacer next to the ring had a tiny nib on it; I wonder if that cut into the ring and caused it to fail. I checked the other rings and spacers and found another plastic spacer with a nib and a ring with some excess rubber attached to it. When installing the coupler, I would inspect the rings and spacers to be sure they are in good shape. I put everything back together and ran it for about 30 minutes with no leaks.