Heater Core Firewall Junction/Coupler bypass - DIY write-up

[98 V70 WIP]

There are (2) larger O-rings inside the body of each junction firewall coupler which fit below mentioned Gates hose nicely. I used these along with about 2-3 feet of 5/8" Gates gray line heater hose. When placed on the hose shoving it back through the gutted coupler, it seals between the hose and coupler body, eliminating the need for other types of sealants. Luckily, I had a newer coupler and gutted/used it and the O-rings for a seal on both ends of each hose. Just my take on it. I improvised and had fun with it!

[j-dawg]

Quick update - as part of what ended up being a year-long engine-out project, I replaced the heater core with a new Behr unit, since I got it cheap. Not a single drop of coolant leaked anywhere, the heater hoses are still supple, and the brass elbows (5/8" 90-degree pieces from McMaster-Carr) show no signs of corrosion. All this after four years of regular usage right next to the turbo.

[abscate]

August 2020

I have a bunch of the Gates 5/8 hose if anyone needs this for tbypass

Reach out on PM or EM

[Eddystone]

@Lee: Yes, I ran hoses straight from the block and coolant pipe through the gutted coupler, to the heater core. But it was on a non-turbo; to avoid hose kinking I cut the hoses long enough to make small loops in the engine bay. I don't know if there is room for that in the turbo engine bay.

I just did the 5/8" hose from the engine to the OEM pipe ends and reused the coupling with new clips and o-rings.

First, I wanted to point out that getting the metal fittings OFF of the OEM hoses requires the right kind of tool (a Dremel with a reinforced cutoff wheel) because those "crimpers" are made of thick hard metal, not anything flimsy. The Dremel makes fairly quick work of it.

Second, the fact that standard 5/8" hose is not molded for the corners means that you do, indeed, have to add some length to make the proper loops. If you don't, the hoses will definitely kink. Don't cut them to length until you know how long they need to be.

[abscate]

Anecdotally , most of the problems reported here result from hose removal cracking the plastic bulkhead fitting. For engine work this is avoidable by releasing the hoses at the block of course.