My throttle body started leaking coolet out the lower fitting about a month ago. It got worst and with Christmas around the corner, I'm not going to shuck out $600 for a new TB. I tried JB wield and other sealers and nothing worked.

So, I bypassed it!!!!!

From all the reading I've done about it, all the coolet does is help the TB warm up the engine when it's cold out. Now, I have always read that cold air is better for an engine, cold air means denser air molecules which helps atomize fuel.

Since I've bypassed the TB the truck idles much smoother and I actually get better gas mileage. My 91 F150 is getting 15.5 MPG vs 12MPG. I rebuilt my engine around 3000 miles ago.

Just thought I would share some info.

Jim

 

Yes, there was a thread in the Big Bronco forum about this. It has it's good points but also it's bad points. I will see if I can find it. EDIT: Here it is: https://www.ford-trucks.com/forums/s...ghlight=bypass+

-Matt

 

The primary purpose of the heated throttle body is the prevention of ice accumulation in very cold climates. The pressure drop at the throttle blades can potentially cause ice to form at that point. This could then block the throttle partway open, which could be a problem if you are approaching a sharp corner on any icy road. I think the automakers add this feature for everybody for fear of product liability for the 0.1 percent of users that could potentially experience this.

There are many who advocate bypassing the throttle body heating for performance reasons. I have seen some solid scientific analysis that basically ridicules the idea that the throttle body can signficantly heat the intake air at full throttle. I agree with this analysis and believe there is no benefit to deliberately bypassing the coolant around the throttle body.

If you have a problem with the coolant lines and you don't live in North Dakota, go ahead and bypass around the throttle body. But there is no good reason to disconnect a working system in search of better performance.

Cooler, denser air means more peak power potential at full throttle. (More oxygen mass per unit volume of air.) But if the throttle is partway closed, there is no need for "more" air. Warmer air generally does a better job of evaporating fuel, and achieves a better mixture distribution than does colder air, thus better mileage.

But I don't think the throttle body heat makes much difference, one way or the other, to the temperature of the intake air. The temperature of the engine in general, does make a difference. The temperature of the intake plenum, the runners, the cylinder head, and the intake valves makes a difference. But the throttle body is too small, and there is too little area in contact with the air stream, to signifcantly impact the temperature if the cylinder charge.