What / why is a bypass thermostat?

Unknown

Continuing from the thread:

thermistat installation



I had been running with a standard "disk shaped" thermostat. The housing itself has a bypass, or so it appears. So I'm guessing that some of the water flows when the thermostat is closed. My temp sender is wrong, but the engine never seemed to overheat.



What the heck is a bypass thermostat? Am I hurting my engine by not running with one? Why do I need one if the housing has a bypass?



The last poster on the previous thread talked about using a therm and drilling a hole in it and blocking off the housing bypass. Why do that? Why does it matter if the water passes thru a hole in the therm or passes thru the original bypass?



-Chris

Geoff

A by-pass thermostat is one which closes off the main orifice, yet lets the water re-circulate around the block, giving more even and quicker warm-up. This gives better circulation for th heater as well. The non-by-pass has a small hole to allow the water to circulate a little amount. This is necessary to allow the warmth to actuate the bellows of the thermostat. With no hole you would have to wait for normal convection heat to warm the water around the bellows, and could lead to pressure build-up and hot spots int he block and head.

Geoff.

Jon B

dave s

usgrant7 wrote:

Continuing from the thread:

thermistat installation



I had been running with a standard "disk shaped" thermostat. The housing itself has a bypass, or so it appears. So I'm guessing that some of the water flows when the thermostat is closed. My temp sender is wrong, but the engine never seemed to overheat.



What the heck is a bypass thermostat? Am I hurting my engine by not running with one? Why do I need one if the housing has a bypass?



The last poster on the previous thread talked about using a therm and drilling a hole in it and blocking off the housing bypass. Why do that? Why does it matter if the water passes thru a hole in the therm or passes thru the original bypass?



-Chris

The talk about drilling 1/8" hole was into a softplug that is inserted into round opening in bypass. With it blocked off, you can use regular thermostat.

Unknown

dave s wrote:

The talk about drilling 1/8" hole was into a softplug that is inserted into round opening in bypass. With it blocked off, you can use regular thermostat.

Ahhhh. So if you use a regular thermostat and leave the bypass unmodified, the thermostat may not open, or open too late.



Well, I think my Hudson has been running a little hot actually. I just fired it up and ran with no thermostat, and the gauge went from hot to 1/3. I have the wrong sender, but I suspect the sender registers 0 ohms for "very hot" (and the needle pegs at cold) whereas now I think it's at about 15 ohms (needle shows 1/3) and the engine is cooler.



I'm not going to put a thermostat in until I get the right sender. No sense in playing with an equasion with 2 variables.



Thanks for the info;

-Chris

Unknown

us grant . When I first got my wasp it overheated and kept throwing coolant out and I couldn't figure out why. I discovered there was no thermostat at all in the engine. Not being able to readily access an actual hudson type thermostat I read on a site somewhere, Ken Cate's hudson page I believe, that a later more modern thermostat could be used as long as a hole is drilled in it to allow for a little bit of coolant to circulate as well as air to be released. I drilled a 1/8 hole in the actual thermostat itself and installed it. I made a gasket to fit that blocked off the bypass in the thermostat housing and Voila!...works like a charm.

Unknown

I guess I forgot to mention the reason I posted that last post...DON'T run your engine without a thermostat...you'll have nothing but trouble.....my 2 cents...Goodluck...Jim

mars55

If you run a non-standard thermostat, you need to block off the bypass passage in the housing. Otherwise, some of the hot coolant is circulated back in to the block without going through the radiator. This could cause over-heating on a hot day.

dave s

Here is softplug installed with1/8" hole.

HUDSONNUT

What type of "trouble" would a person have going without a thermostat? Right now I'm running my car w/o a thermostat and with the plug in the bypass for the thermostat housing. I had to take the thermostat out, as I had a bad one, and haven't gotton back to putting it back in yet.

Geoff

YOu have two problems, running too cold in cold weather, and too hot in hot weather. Without a thermostat the water will circulate flat out all the time. In cold weather this means the engine will run too cold. in hot weather, it is not held in the raidator long enough to cool properly, hence will tend to over heat. The thermostat is actually a circulation regulator, opening enough when it gets up to temperature to allow the coolant to circulate, as soon as the temperature around it drops, it closes again, ad infinitum. Hence, the water is hled longer in the raidator, giving it a chance to cool down more. Hence it is essential to use anti-freeze in cold climates, as with the water flow blocked off, it could freeze the radiator.

Geoff.

Unknown

the car will throw the coolant out and run hot