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Discussion Starter · #1 ·
Hey guys, I'm trying to fix a leak in my cabin that seems to be originating from the heater core valve I replaced last year. My suspicion was that the hex screws came loose, but that didn't fix the problem. My second intuition was that the o-rings were split, but when I took it apart, they were merely flat, but were intact. I have the plastic scan-tech one though, and the 6 screws that hold the cooling system inlet/outlet ports to the valve itself were loose, and so I think this is the problem. However, I really don't want to take the whole thing apart and drain the coolant just for this again, so I'm wondering if I can replace both the o-rings (between the valve and the heater core) with a silicone RTV gasket maker designed for cooling systems? Any thoughts on this?

li Arc
 

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Did you tighten up the screws? That might be enough...

Otherwise, you're going to have to open the cooling system to address this anyhow. I would suggest you get a short length of 22mm copper pipe, loosen the hoses from the valve in the engine bay and join them together with the copper pipe. That will minimise your coolant loss from the engine if you do it quickly. The heater core will not drain when you remove the valve as its flange points up. New O-rings should be easy enough to get and would probably be better than the sealant. That said, if you fill the o-ring grooves in the valve flange and leave them slightly proud, they should seal well enough.
 

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If you over tighten the screws on a Scan tech heater control valve it causes the plastic to bend slightly. That could cause a leak.

I cleaned up the mating surfaces, put the O rings in the grooves, apply blue Hylomar to the mating surfaces, screw togehter, but do not over tighten screws. You can see when the plastic starts to bend.

I have had no leaks so far using this method.
 

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Discussion Starter · #4 ·
Well, that didn't help at all :( It's still leaking, and it'll be the third (and last) time I am taking this thing apart. I want it to work 100%, no exceptions, no possibility of failure. The old o-rings are too flat I think, and so it's not sealing properly.

I bought some heavy duty hydraulic operating equipment o-ring seals in hopes that this will help, as I don't have replacements for these. I assume since hydraulics are much higher pressure, it can take a cooling systems' pressure. And since it's built for much tougher conditions, it should hold in the heat. They are slightly oversized, which may be very tight in the grooves, but I think this might give the best seal. I'll make sure not to overtighten the hex screws, but I'm not too confident in them holding without enough torque. Thoughts? Like I said, no more break downs, and I don't have the right parts, but I need it done ASAP while it's still warm enough to do this stuff!

li Arc
 

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I would not reuse O rings. Use new ones.

What I described was using a new Scan Tech heater control valve kit which includes O rings.

It is possible that the plastic mating surface is slightly bent causing the leak, or otherwise it is likely the old O rings no longer seal.

I would put in a new heater control valve.
 

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definately get a new valve with the rings. if they are too heavy duty then it wont seal, if they are too old and smashed down it wont seal. I was worried that I didnt tighten the valve right on mine but it worked out perfectly. The square nut that you screw into was the wrong one and it broke some of the plastic on my valve. so I used the old nut and then it worked. no drips yet. Just put it in last night.
 

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Discussion Starter · #7 ·
This valve is a year old though...does this mean I have to replace my valve once every year!? :eek:

li Arc
 

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If you know its just the gaskets and its only a year old then just order the gaskets from eeuroparts. make sure you dont overtighten the valve to the core. you will blow out the gasket if it is over tightened.
 

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li Arc said:
This valve is a year old though...does this mean I have to replace my valve once every year!? :eek:
No. New O rings may solve the problem, but if the plastic is now permanently bent, it might not. Hence my suggestion to get a new heater control valve kit.

You might have to take it all apart again if new O ring seals do not fix the leak.
 
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