My plastic heater control valve broke a couple of weeks ago. It dumped coolant all over the right side header. Anyway, I have the older style two inlet valve not the newer style three inlet/outlet piece. I checked with Kragen, Pep Boys, and Auto Zone, none of them stock it. I ended up buying one from Napa. I installed the new valve, went to work, and when I did a downshift near my house, the diaphragm in the vacuumn pot ruptured. I took it back to Napa to exchange it, and this time I got a bypass nipple. I ran the engine in my driveway with a Snap-on cooling system tester for over an hour. The system pressure maintained 7# at 180 degrees, when the temp went to @210 degrees before turning on the fan, the pressure went to 8#. I then shut off the engine, and pumped the pressure up to 17# and left it overnight. The system held pressure, so I changed the valve again. I took the car out, and had the second new valve from Napa fail in about 5 miles. Same failure. I went to Chevy, and bought a new valve which I put in after work today, so far it is holding fine. Moral of the story, G.M.'s Mexican parts seem to be better than Napa's Chinese parts. Is there anything on my car that is actually made in USA?

 

Russ, I have been told countless times by many people on these boards that we actually don't need to even run that bypass vavle as originally plumbed into the cars. GM put it in there to reduce the heater core temps about 5 degrees in an attempt for the A/C to blow cooler but everyone insists that it works the same whether the valve is there or not. I am planning on deleting it out of my new cooling system entirely, beside, my new system should maintain about a constant 172* like the setup I have in my worktruck that never gets hotter even carrying a work payload of about 2500Lbs in the bed going uphill to a jobsite in say anahiem hills.

Dean

 

Some cars didnt even come with them, like my 85 and 86 TPI cars... never had em.

 

Interesting, I never considered just bypassing that valve before.

 

When I had the straight tube in bypassing the valve, I couldn't get any heat or defrost. I still don't understand how it works. It would appear that the coolant goes through the valve to get to the heater core, but since it won't heat without the valve, it doesn't work the way I thought it did.

 

I have a trick but pretty expensive entire cooling system setup I will install by summertime that will delete the bypass valve entirely and route the manifold exit feed to the heater core directly via Earls lines and fittings. The custom all brass 4-core radiator that Hoffman built for me about 5 years ago for about $200 is already restricting flow- piece of crap. This motor was getting hot last summer with the A/C on at freeway speeds but not at idle.

The trick part of the section of hose is it will have coupled AN male to male inserts in the middle of both the "manifold -to-heatercore" assembly and the "heatercore-to-radiator" hose assembly that in the event WHEN (because it will happen one day and I'll be stuck roadside) the heatercore lets go from age, I can simply uncouple the AN connetors and reroute the manifold exit directly to the radiator to get me home and about until I change out the PITA heatercore assembly. Its about $80 extra in plumbing, but I feel well worth it because you never know when sh*t happens.

 

Its a simple system. You have a manifold exit to the heater core, and a line from the heater core to the radiator.

Russ, what did you do with the vacuum line? Pretty sure it runs to the HVAC controls under the dash and you probably had a leak that didnt allow the door to open.

 

I had the vaccuum line plugged off. I think it should have another vaccuum line to operate the door under the dash, but I was expecting to have heat at whatever outlet is the default. I turned on the fan on the way to work, and had cold air everywhere.

 

Thats funny I just bought one from autozone on warner in huntington beach yesterday morning.

 

You probably got the new style three outlet valve. Mine is the older style one inlet, one outlet with a vacuum pot on top. Autozone, Kragen, and Pep Boys all had the new style valve, but only Napa had the old style in stock. Like I said, I tried two of the Napa valves and both failed in minutes of installation. The new one I got from G.M. has been in for a few days without a problem.

 

Sorry dude I guess that makes a big difference. I hope you get it taken care of

 

It is done, just went to Chevy and bought the right part.