heater bypass valves

dburdick

dburdick

doug b
I am using an in head thermostat in the 2lt fiat engine I installed in my 76 scorp. Fiat used these for awhile, but stopped, because apparently, when your not running the heater, the flow from the outlet side of the cylinder head( rear of the head, near #4 cylinder) would be interupted, causing overheating issues and head gasket failer. I hate the inline thermostat setup, and was determined to find a solution. DJ.Richards, who contributes to the Lancisti Community forum, gave me an idea using a '79 cadallic three way heater valve. I have expanded on his system by using two of them. The result is that if the heat is turned on, all flow from the head goes through the heater core, then to the suction side of the water pump. When the heat is turned off, all flow goes from the head to the suction side of the pump, none to the heater. I did this through the use of a dual circuit relay, four electric air valves(two to direct vacuume to one valve or the other, the other two bleed off vacuume to the valve not in use so it can reopen) and my LED switch system for my HVAC. This assures me that I have constant flow from the head, either to the heater or the pump. Probably unnecessary, but this is why this is called a hobby!



 
This is one I have thought a good bit about.

My first question is, does the #4 cylinder actually have a higher incidence of failures? Personally I have never seen this to be true and this is only the second anecdotal reference I have seen. The other was on the Spider forum. I am not saying you are wrong.

So the normal flow is across the head to the outlet either to the thermostat or off to the radiator. When there is a call for heat hot coolant is bled of to circulate hot material to the heater core. This coolant gains some measure of heat disapation from the core and the intervening lines. It is then drawn into water pump displacing fully cooled water from the radiator or off the thermostat hot side when warming up.

This is the thing that concerns me about your system, you are drawing fully heated water directly into the flow of coolant that should be more conditioned. This arrangement could very well create a situation where the engine actually tends to run hotter than it should and something the thermostatic system cannot control.

An ideal arrangement might be a bit different, when there is a call for heat in the passenger compartment the full flow would be through the heater core and then into the back of the pump which when the car is warming up could assist in it getting there quicker. If there was no call for heat, the coolant from the #4 cylinder area would be fully diverted to the line that leads to the radiator thus ensuring it gets cooled and the engine is receiving the full measure of fully cooled coolant rather than a much hotter mixture as a result of #4 hot coolant being drawn into the pump.

By adding a tee into the line leading to the radiator you could use your cuurent valve and control set up to achieve this. I believe this would be closer to what you are really trying to do which is have good heat and a well cooled engine during those hot days and in traffic.

This is clearly my opinion and you are free to ignore it but it's something you might wish to think about.

All the best, and thanks for sharing.

By the way could you someday please tell us more about your electronic control system, it is very unusual and interesting. You seem to have created something which offers options the original systems in these cars could never have offered.

Karl
 
Yep!

Yep Karl, you're right!routeing flow straight from the outlet at the back of the head will not only introduce uncooled water right back into the engine, it will also act as a recirc loop that will reduce flow from the themostat outlet to the radaitor, not the effect I want at all! Tomorrow I will fit a "t" in the hose after the thermostat to introduce the water from the rear outlet to the outgoing water leaving the engine. Great idea and thanks! As to the "why" for all of this plumbing maddness, I'm running 8mm dome pistons in my 2lt fiat engine, and the compression is around 195-200 PSI per cylinder. This was a mistake.Unless you like filling up with 93 octane all the time, don't do what I did! I have installed a felpro head gasket from auto ricumbia, and I check the torque on the head bolts every 5k, and have had no futher problems. The airvaves are units I buy from a supplier on ebay, and work great for routeing vaccume in this crazy setup of mine. A single, dual circuit relay switches the vaccume valves from one set to another. I have had massive overheating problems in the past, even back when I had the stock 1800cc engine in the scorp.It wasn't the headgasket then, I never did figure out the problem. I had the radiator boiled out and flow checked, built a 2lt engine(with too much compression!) and went from there. I replumbed the cooling system with an in head stat, and drilled and taped a spout on top of the stat housing and run a small hose to the top of an X1/9 stainless tank to catch any air passing through the system. So I'm just trying to improve cooling throughout the engine, especially the back side where flow is normally poor, if the heater is valved out. I'll write back tomorrow after I've fitted the "t" and let you know how it works. Thanks for your interest! Doug.
 
You might consider looking at Bob Browns thread about an auxiliary electric water pump. As I recall it was one intended for use with a turbo after run pump to keep coolant running through after shut down to keep the oil in a turbo from cooking off.

I know VW has a similar pump for their VR6 motors as well.

Glad I could assist in some small way. All the best and keep us in the loop as you perform additional updates and upgrades.

Karl
 
That post is here...

Look HERE for the entire post.
This was a project that had un unknown outcome when I started, a lot of speculation in between and a very nice outcome in the end. :)
 
I was thinking

about using the electric water pump from one of the old '80s model Mercedes 190s. That pump was used for a simular purpose, in this case, to make sure hot water was circulating through the heater in slow traffic. Wonder if that would work as well?
 
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