I looking at making a manual shutoff for the heater core. I was thinking about using a CPVC 1/2" valve with a short (2") piece of 1/2" CPVC pipe out of each end. The 1/2" CPVC is 5/8" around the outer diameter so the small 5/8" heater core hose will fit nicely with some screw clamps. I guess the real question is will the antifreeze react with the CPVC and cause a problem?

thanks,
phil

 

I wouldn't trust PVC but that's not my primary objection to this mod. You really don't want to shut off the flow, you want to simply route it past the heater core. Your water pump and engine need to have some flow through them, even when the thermostat is closed and the engine isn't fully warmed up. On most engines this is accomplished by the coolant that constantly flows through the heater hoses/heater core.

If you look at most stock factory systems, like the kind supplied on most (all?) stock 3rd gens there is a heater core bypass valve that is activated under certain conditions. It does not STOP flow through the core, it merely routes it through a 3rd bypass hose so it goes AROUND the heater core. But flow is still allowed. You should try to emulate that basic functioning with your modified system.

As an alternate suggestion- you might want to simply use a stock heater core bypass valve along with a bypass hose. The valve's operation is simple- if vacuum is supplied to the valve's control diaphragm it bypasses the heater core and sends coolant through a 3rd hose (the bypass hose). If there is no vacuum supplied it allows coolant to flow through the heater core like normal. You could easily turn it into a manual valve by either hooking it's vacuum control hose to a convenient source of engine vacuum (to bypass) or leave it disconnected (to allow flow through the heater core).

Wondering- what is the reason you want a manual shut-off?

 

I have an 83 Z28 which had no factory "bypass". I now drive my car in the summers only and am getting tired of the hot air on my feet. I have not restored the A/C yet so I wanted to try to key the cabin as cool as possible. I read in other posts that a simple shut off would work fine. I have seen the valve you are talking about but I am not sure how to hook it up. Does the bypass hose "T" into the return line for the heater core? Maybe a diagram.

here is the link that i saw:

https://www.thirdgen.org/techbb2/sho...ter+AND+bypass


thanks, phil

 

That's the thread I started. Looks like conflicting info. Some people say the stock control valve blocks the flow, not diverts it. ?!?!?

I thought coolant always circulates through the block, then when it warms up, the thermostat lets it flow through the rad??

 

Coolant always circulates through the heater hoses regardless of whether the stat is open or not. The factory bypass simply routes it through a 3rd bypass hose, effectively taking the heater core out of the loop- but the coolant still circulates. It if was just a shut-off valve there would be no 3rd hose.

A factory bypass-type heater hose routing would look like this:

Hose comes from the intake manifold water crossover (either from the front or rear, depending on where the facotry decided to tap in on that particular year). My 92 5.0 TBI engine happens to take it from the rear, but it varies year-to-year and engine-to-engine. Regardless, the intake manifold is where the hot water exits the engine.

From there it goes to the inlet of the bypass valve. There are 3 hose fittings. 2 in a row and 1 pointing off at 90*. The inlet is the fitting that points off at 90*.

From there it goes to one of the two outlets, depending on whether the vacuum diaphragm has vacuum applied to it or not (the vacuum diaphragm is on top of the valve):

1. The bottom fitting goes to the heater core inlet.

2. The top fitting goes to the bypass line.

If it goes through the bypass line it proceeds directly down to the heater core OUTLET hose about 1/2 way between the heater core and the radiator where it junctions into it via a "T" fitting.

 

if you go to partsamerica.com (Advance Auto) and search for "heater valve" for a 87 Camaro, they have 2 different types. One with 2 fittings

http://www.partsamerica.com/PartDeta...pe=394&PTSet=A

And one with 3 fittings...

http://www.partsamerica.com/PartDeta...pe=394&PTSet=A

Which makes me think that either would work.

 

Another reference i found on the web is this Monte Carlo SS with a L69. Note the 2 fitting heater valve.

 

After checking my shop manual, I verified I only need a shut off valve, not a diverter valve. I bought mine at Home Depot for a few bucks and spliced it in. So far so good. Once I shut it off, even if I turn the HVAC to full heat, I get cool air. It's about time!