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I am doing my engine over and was considering installing heater core bypass valves. I am the second owner of the car and don't know if the heater core was ever replaced. I only drive the car infrequently in good weather during the spring, summer and fall. I could close off the fittings on the water pump and intake manifold, but I would like the ability to use the heat and defroster if necessary. The core doesn't leak now and I only use a 7lb radiator cap, but I am thinking if it ever started to leak I could just close the valves on the intake and output hoses and this would limit the amount of coolant that leaked inside the car. Does anyone recommend a good less intrusive bypass valve? Also, is it fairly easy to check the condition of the heater core and replace it if necessary while the engine is out of the car?
Hi Miccar, some additional information would be helpful for you to receive good direction. What year is your car? What engine? Does it have a/c? Other than the 7 lb cap, is the cooling system stock? Let us know that and we can give better help.
The answers to these question may drive very different suggestions. For example, if you don't have a/c I would definitely recommend that you replace the heater core - it's not that hard without a/c. Thanks, Paul
The car is a 1972 350 with an automatic transmission and power steering. That is it. It doesn't have air conditioning. The 7lb radiator cap was on the car when I purchased it almost 12 years ago. I was told this cap puts less stress on the cooling system. It used to puke a little coolant on the ground, but that was my fault as I always filled the coolant to just under the radiator cap. There have never been any cooling system leaks since I owned the car. Years ago I did install a plastic coolant recovery tank. I am having all new hoses, water pump, 180 degree thermostat installed and having the cooling system flushed. The rebuilt 350 will have a hydraulic roller cam with roller tip rockers and aluminum heads and intake manifold. The car also has long tube 1 5/8" headers. I am having the engine built to idle smoothly yet develop more low and mid range torque and hp as the car is a cruiser and car show type of car. It isn't raced or abused. I had also heard installing aluminum heads lowers engine operating temperatures, but now I am hearing this actually raises the coolant temperatures.
Assuming AC was never in the car, I have a 78 without AC and it took me 45 minutes which included a break, to change the heater core out. Here is a vid of a 74 (might need to turn on the volume, click the top left) and there are only about 7 nuts and done from inside the engine compartment. https://www.dailymotion.com/video/x2su2vm
Hey Miccar, sounds like you have a nice C3. We need pics. The above advice is great. A couple of thoughts:
Our '68 bb also has no a/c. Since I was doing a complete under hood cleanup, I replaced our heater core from inside the engine compartment. I wanted to clean up the box, fan motor, vacuum can, etc. anyway. It was really ezpz once I figured out a couple clips inside the box.
When you remove the heater hoses, don't wiggle them off (same with radiator hoses). Take a sharp blade and slice the hoses longitudinally, then use a small screwdriver to 'lift' them off the heater core inlet/outlet. Wiggling them will almost certainly ensure that the inlet/outlet come a bit loose where they're brazed at the core.
Your stock cooling system will handle the cooling chores no problem as long as: you have the right fan blade; the radiator is good with no core rows soldered off (if you need a new radiator, DeWitts make a direct fit that slides right in perfectly. We put one in our '68 and it works great); the fan clutch is in good shape; the right radiator cap is on; your water pump is good; 180 stat as you stated; good hoses (be sure the spring is in the lower hose); fan shroud is in place with all the foam stripes there; 50/50; etc.
I got 2 shutoffs from Home Depot for about $15 and spliced them into the lines/hoses. I never use the heater but all I need to do is flip the levers if I want to.
There's no need for 2 shutoff valves. No hot coolant is getting to the heater core, therefore the heater core doesn't get hot. GM NEVER used 2 heater control valves on any car of that era.
I agree with the theory that a single cut-off should be sufficient. @interpon found otherwise when he actually tested it. Even with both lines blocked, the hoses live in the hot engine compartment. I'd encourage you to read his thread.
Blocking the ports with NPT plugs eliminated the problem in my cars, and removed any chance of leaking.
Thanks guys. I just want the two valves as a safety precaution in case my heater core develops a leak. If it ever leaks I can shut both valves and it will limit the coolant spilling onto the carpet and I can still drive the car.
You live in a part of the country that may need Defog even in the summer.
And that is why you should never completely remove a heater cores function.
In Sunflowers above post about N.A.P.A. At the bottom of the NAPA ad is the shut-off I installed. Around $26, simple petcock style allows some flow if you so desire.
You can hide the valve down closer to the firewall if you choose, and still have easy access to the lever.
They come in 5/8 or 3/4.
You are not the original owner and do not know if the heater core has ever been changed therefore that core could be 52 years old.While you have everything out of the engine compartment it would be a good idea to replace it. Since you are having all this work done on the car another $120 wont matter much & it will give you the opportunity to clean out behind the cover(and blower fan) where critters might have made a nest.
Heater Core Bypass Questions
