Does everyone have a thermostat bypass?

[WardL]

I found out this summer I didn't have a thermostat bypass. Bought the Cobra used in March and I noticed the water temp was very dependent on the ambient air temp. In the pacific northwet, a 50 F day is not unusual. The engine manufacturer strongly recommends a bypass, but Cobra came from hot climates and maybe the standard down south is no bypass? The bypass is typically a short 5/8" hose from the thermostat housing to the top hole in the water pump case. I'm sure there are other configurations. I plan on putting in a bypass and see how much difference that makes, but I'm curious how common it is to not have a bypass. Let me know, thanks.

[Barnsnake]

It sounds to me like you don't have a thermostat or it is stuck open. When you put in an operating thermostat, install the bypass. Drill a couple of tiny holes (~1/16") at the top of the thermostat to let the air out of the cooling system when filling.
It's possible someone pulled the thermostat because of strange behavior due to the lack of a bypass.

[bobcowan]

Agree with the above: check the thermostat.

The bypass hose plays an important role. The normal flow of water is through the block from front to back, up to the rear of the heads, and then through the heads from rear to front, and then out the open thermostat. During warm up the thermostat is closed. Water then flows through the bypass hose, and back into the water pump. That keeps water flowing through the engine for an even warm up, and prevents hot spots.

A smart builder would only remove the bypass hose if the thermostat was also removed. But you would really only want to do that on a race only engine. Not a good idea for a street engine.

[Rwillia4]

Don't drill holes in the t-stat, instead install the by-pass hose. Drilling holes allows water to go through the t-stat which serves the same funtion as having the hose installed.

With the limited amount of information given I'm not sure why Barnsnake thinks you don't have a t-stat installed. Have you ever had a problem with the car overheating on a warm day?

[Gaz64]

Originally Posted by bobcowan

Agree with the above: check the thermostat.

The bypass hose plays an important role. The normal flow of water is through the block from front to back, up to the rear of the heads, and then through the heads from rear to front, and then out the open thermostat. During warm up the thermostat is closed. Water then flows through the bypass hose, and back into the water pump. That keeps water flowing through the engine for an even warm up, and prevents hot spots.

A smart builder would only remove the bypass hose if the thermostat was also removed. But you would really only want to do that on a race only engine. Not a good idea for a street engine.

Very well said Bob, could not agree more.

I teach automotive to apprentices.

I can't count the number of cars I've seen who don't run what they "should be" running.
I walk away in disbelief sometimes.

[Gaz64]

Originally Posted by Rwillia4

Don't drill holes in the t-stat, instead install the by-pass hose. Drilling holes allows water to go through the t-stat which serves the same funtion as having the hose installed.

With the limited amount of information given I'm not sure why Barnsnake thinks you don't have a t-stat installed. Have you ever had a problem with the car overheating on a warm day?

Drilling holes in the thermostat and no bypass hose is not the same as a normal thermostat with a bypass hose.

A normal system with a bypass (internal or external) allows fast engine AND heater warm up
WITH circulation prior to the thermostat opening point allowing coolant flow to the radiator.

The is no point in allowing coolant flow through the radiator in the warm up phase,
we only want circulation within the engine.

[rustyBob]

they come from the factory with a bypass hose.....those guys must know what they are doing.....

[Bob In Ct]

Does the word "cavitation" strike a familiar note? Use a bypass and a thermostat.

Bob

[bobcowan]

Originally Posted by Rwillia4

Don't drill holes in the t-stat, instead install the by-pass hose. Drilling holes allows water to go through the t-stat which serves the same funtion as having the hose installed.

With the limited amount of information given I'm not sure why Barnsnake thinks you don't have a t-stat installed. Have you ever had a problem with the car overheating on a warm day?

Drilling a hole in th thermostat is a common SBF trick. It makes the system open, and allows air and fluid to easily move through the entire system when cold. That almost eliminates all burping and filling problems. I'v been doing it for decades. A single 1/8" hole is all you really need.

It does not perform the same function as a the bypass hose. The bypass hose directs coolant back to the water pump, and back into the front of the block. The hole allows coolant and air to flow through the upper radiater hose, past the filler neck, and to the radiater.

It does extend the warm up time a tad. But only a tad. Not enough to notice or effect function. How much fluid can a 1/8" hole pass?

A symptoms of an open or missing thermostat is that it never warms up on a cool day. The thermostat controls minimum temp, not max. Excess engine wear occurs at temps <160* or so. And oil won't function properly at temps <180*'ish.

The other issue with a missing thermostat is the speed of the water flow. The coolant must be in contact with a hot surface long enough to transfer the heat. If there's no thermostat at all, the heads will get really hot, even though the coolant temp is low or normal. That's why racers will remove the thermostat, but install a restricter plate. Or just gut the thermostat.

[Ant]

Originally Posted by Gaz64

Drilling holes in the thermostat and no bypass hose is not the same as a normal thermostat with a bypass hose.

A normal system with a bypass (internal or external) allows fast engine AND heater warm up
WITH circulation prior to the thermostat opening point allowing coolant flow to the radiator.

The is no point in allowing coolant flow through the radiator in the warm up phase,
we only want circulation within the engine.

The small hole you drill at the top of thermostat base plate is an air bleed not really a bypass due to minimal water flow.

We run a remote t/stat with bypass from engine side of t/stat back in to the bottom hose, this can be -6an or -8an or equivalent sizing.

[vector1]

two 1/8" holes in the thermostat and no bypass any day of the week over a stuck thermostat and bypass hose.

[timsullivan]

Running bypass? Absolutely!

[WardL]

I've never had an overheating problem. I'm installing a bypass and will confirm I've got a thermostat before I drive it again. It will be interesting if it has holes in the thermostat or not. Thanks,

[Snakebit]

I have a Weber set up and with out a bypass hose I could not get the temp above 160. Installed a bypass hose and it stays at 180.