Thread: Coolant flow through TB?

You could give it a shot. That or you'll have to let it run for a bit and watch it. Either way, no problem really.

IIRC the coolant running through the TB is to prevent carbon build up. I have routed my coolant lines from the TB to the turbo. I have also eliminated my coolant lines going through the EGR valve since I dont have one. I also dont think the coolant lines have anything to do with keeping the throttle plate from freezing up, I would think the engine bay temp would suffice unless you lived in the arctic circle.

Now on the comment to tapping the block for the coolant lines, I would think that would make more fail points than tapping into or by passing the TB.

Big Ben, water through the throttle body is to keep the throttle from freezing (usually open) in cold climates. Hundreds of cubic feet per minute of below freezing air can freeze a throttle open quite easily. It's not really up for debate.


I too put quite a bit of thought into which direction I thought the water would flow through the system before plumbing my turbo. I didn't have the luxury to run the engine and find out for sure but I looked at the coolant pipes and where the water comes from and where pressure builds, and where the hot water is and decided I was confident which way the water traveled and plumbed the turbo accordingly (sorry I don't remember which way otherwise I would have posted earlier). I'm real curious as to what you find out.

I by-passed both the TB and the EGR sections and have only the turbo getting water but I wanted to know which way it flowed so I could take advantage of gravity and convection to help cool the turbo after engine shut-down. These are important things to me.

Well I guess i have been told!! Sorry I just never saw that really happening. You learn something everyday.

You are both correct

An engineering professor of mine a few years ago came to class late one morning because the throttle on his Saturn froze open on the highway. This was in Milwaukee (not the coldest place around) on a random winter day. He had to shut the car off to avoid crashing.

As far as turbo plumbing, am I correct to assume that you'd want to run a line off somewhere between the water pump and the thermostat? On the engine side, not the radiator side. If you were to shut the pump off, it seems that's where pressure would reside the longest once the T-stat closed. A line, for example, from the throttle body hose to turbo, and then over to the radiator side?

A trick Toyota owners apparently don't know about

Danja the real trick for turbo water lines is to try to make sure the water coming to the turbo is coming from a "cold" source and the water leaving the turbo goes to a "hot" source and in general the lines go uphill (against gravity) from cold inlet to hot outlet.

Once the engine is shut off you're relying on convection to keep the flow through the turbo and that is why you want cold down low and hot up high and the direction of flow should coincide with that so you're not fighting against pressures in the wrong direction.

(For those with electric pumps they run after engine shutdown none of this really matters.)

I'm not exactly sure on all engine models but I think that those lines get have a venturi effect rather than a gravitational one. They are both coming from the thermostat but one pipe is larger than the other. That it the way it seemed the last time I saw my pipe and it was still intact.

Here is the link for everyone
Venturi effect - Wikipedia, the free encyclopedia

Jere I believe you're right about that. However that's while the engine is running. I too recall the TB and EGR systems get flow because of the difference in pressures due to the difference in pipe diameters just like you said. However once the engine is shut off and the water pump stops it's up to convection.