Not Using Heater...Still need to use bypass thermostat?

[thekid1950]

1949 Plymouth Special Deluxe

 

I'm cleaning up my cooling system.   New Radiator, New water pump, New thermostat, New hoses....

 

I don't use my heater....it is DISCONNECTED.

 

Question?  Should I get a bypass thermostat that will allow the system to operate as designed?  It appears to me the bypass just provides hot water to the heater.

 

Is there any other function of the bypass?

 

Otherwise, I will just use a modern thermostat....

 

Am I missing something??????

 

Thank you!

[greg g]

Many people run without a t stat but the lack of one can actually lead to a higher operating temp than a system with a t stat. This seems counterintuitive but part of the T stats job is to restrict the flow of coolant going to the radiator.  That allows the coolant less time in the radiator where it looses it's heat. Less time in the rad means the coolant goes back into the engine at a hotter temp which then keeps it from absorbing as much heat as it would if it was cooler.  Many folks who ran racing cars fitted a large fender washer with a enlarged hole in place of the T stats to re-establish the correct flow rate.  Lack of the state will also cause it to take longer to get up to proper operating temp which may or may not have consequences in how the engine drives especially in cooler weather.  The bypass keeps coolant in the block thill the stat opens and sends coolant to the radiator.

 

So based on those considerations regardless of heater or not. The T stat is and important component in how the system operates.

[kencombs]

The bypass function is there to prevent hot spots from forming before the thermostat opens.  It allows some circulation, not enough to delay warmup, but keeps it moving around the valve seats in particular.

[blucarsdn]

The purpose of a thermostat is to maintain a constant temp, generally 180 degrees, in an engine. Without a thermostat the engine temp is constantly cycling, hot on the pull and cold on the down hill. An engine that operates below it's designed range will have a shortened life from sludge buildup in the oil and condensation within the block.
A side benefit of a thermostat is faster warm up of the engine on a cold winter day, which makes the engine run better and constant heat for the heater.

The comment about large washers in the upper hose is one of those myths that was started over 60 years ago in a hot rod article written by Vic Edlebrok that pertained to race engines he built.

 

[thekid1950]

Ken

 

Thanks......that is what I thought might be the case.....trying to avoid hot spots prior to thermostat opening.

I've seen some talk before about using a modern stat instead of a bypass one.

I've been to NAPA...their bypass stat doesn't fit in my (49) housing.

I do have a NOS bypass stat I can use

 

Apparently, the bypass allows block water to get to the water pump which then sends it back thru the block & so forth

 

I have other old cars & I usually leave the heater in the on position (without the fan operating) to act like a bypass before the thermostat opens

 

My Plymouth heater core leaks so it is disconnected.....I have a hose that goes from the bypass fitting to the rear of the block where the heater usually returns to water.....I'm sure this also helps avoid hot spots.

[thekid1950]

Yes, I believe in thermostats & would never run without one

 

I think Greg just misunderstood my question with his reply to me.

 

I was thinking of using a modern thermostat (without the bypass feature) but was afraid the bypass was important.  Now I have a better understanding of the bypass & will continue to use it.

 

 

[Jocko_51_B3B]

When the engine is cold the bypass is open which prevents water from flowing up into the radiator. This allows the engine to warm up more quickly. When the coolant gets to about 160 deg F,  the bypass starts to close and the thermostat begins to allow flow to the radiator. Greg g was right when he said that running without a thermostat will cause the engine to run hotter because an open bypass means less coolant flow to the radiator and more coolant flow circulating around uncooled inside the block. This old Chrysler Master Tech video gives a nice clear explanation of the flathead 6 cooling system and talks about all these things. These old videos are a great resource. There's a bunch of them on YouTube.

 

 

[thekid1950]

PERFECT........much appreciate all the responses.

 

That Video is priceless!

[thekid1950]

After watching the video,  I finely realize what I was missing

 

When the thermostat opens a lower part of the thermostat closes the bypass.  I never knew that

 

NOW IT ALL MAKES SENSE!!!!

[greg g]

Also keep in mind the temp rating for the t stat is the point at which it begins to open and allow flow to the radiator.  It doesn't mean your engine will operate at whatever temp it's rated for. Also the top of the radiator is meant to be an expansion area too allow for expansion when the system is up to temp.  If you fill it too full it will eject the excess coolant.  You only need and inch or two additional coolant after the radiator entrance tubes are covered.

Edited March 12, 2019 by greg g

[blucarsdn]

A modern type of pressure cap on the radiator with about 6 lb. pressure and a coolant recovery tank allows the system to purge air from the cooling system which prevents cavitation/air intrainment in the cooling system.
I don't buy ready made coolant recovery tanks. I make them out of a piece of 2" ABS (black plastic) pipe, two caps one of which is glued to the bottom and a couple of barbed brass fitting. One barbed brass fitting is threaded into the bottom cap, the other is threaded into the top cap. Clear plastic tubing is attached to the radiator overflow, then to the bottom  of the tube cap, a second piece of plastic tubing is attached to the upper cap and extended to a point under the car. Attach the overflow tank to the core support using zip ties, etc.

An 18/20" piece of 2" ABS pipe will hold all the fluid that the average cooling can expell, allowing it to return to the engine once the system cools down. To check the coolant level,  check the coolant level in the clear tubing running from the radiator. Add coolant to the tank simply remove the top cap and add enough coolant to half fill the tank. When the engine does a heat/cool cycle the system will draw down the fluid to stablize the level. Of course you can go to your local Hot Rod shop and purchase a fancy S/S recovery tank for about $60. Mine will cost about $20. and does not stick out like a sore thumb. The Rat Rodder types just use a one liter plastic bottle, etc., hung off of a fender brace.