Heater Core Pipe (Leak Fix)

VolvoAffair · Post by **VolvoAffair** » 08 Jun 2018, 18:22

This forum has discussed the replacement heater core distributed by Swedish Car Parts at great length, which is decidedly a great product. Notwithstanding the quality of this product, some Volvo enthusiasts have experienced coolant leaks at the juncture between the heater core and the coolant pipes. The great members of this forum have posited a number of theories and fixes to this problem––chiefly that, OEM O-rings are necessary and that the O-rings provided are of insufficient thickness and/or quality. I respectfully disagree.

I believe the root cause stems from the design of the plastic bracket connecting the aluminum pipes to the heater core. The reliance upon a single machine screw to uniformly tighten and seat the O-rings results in one of two scenarios: i) an O-ring will be pinched or ii) the brass collar will pull free of the plastic bracket before a seal can be obtained. Each results in a leak.

I found that by discarding the T25? screw and utilizing a 4mm screw with a 7mm bolt and washer, I was able to avoid either of these scenarios. The washer helps to distribute force during tightening and provide an even O-ring seal, and the bolt prevents the brass collar from pulling out.

This simple fix enables an assuredly tight seal with the O-rings provided by Swedish Car Parts.
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You will need:

4mm screw
7mm nut
2 flat washers

1/4" drive socket
deep 7mm socket
short 7mm wrench

Note: When installing the screw I found it necessary to use the deep socket to reach it's head due to the narrow gap between the plastic molding on the heater core.

Post by **rguzz** » 08 Jun 2018, 20:20

Nice. Inadvertently I did the same thing because I lost the T25 somewhere in the process of replacing my core. What you have fashioned looks to be a stronger fix.

Post by **abscate** » 08 Jun 2018, 22:57

Maybe a Nylock bolt or a dab of Loctite blue to keep that in place?

If you hacksaw off the cm of extra thread, it will be easier to reinstall, too

Great observation on the O rings

VolvoAffair · Post by **VolvoAffair** » 09 Jun 2018, 08:31

That's a good point, thanks!

Post by **FlyingVolvo** » 09 Jun 2018, 10:18

Nice writeup.

I preemptively replaced my original heater hoses last year and decided to just buy a new OEM coupler. The old one basically fell apart as I removed the heater hoses, so it was a good call.

Post by **abscate** » 09 Jun 2018, 16:16

VolvoAffair wrote: ↑09 Jun 2018, 08:31 That's a good point, thanks!

We thank you for adding To the collective IQ!:

Post by **wizechatmgr** » 09 Jun 2018, 18:10

Looks great. Bet this will fix the minor intermittent leak I was getting late this winter/early spring.