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Throttle body heater bypass on 99 LS1.


Well-known member
Apr 22, 2006
San Diego
99 C5 Convertible
I'm interested on installing a bypass on my vert. I was wondering if it would be OK to run a straight hose from the metal tube by the intake to the radiator. This would eliminate any splicing and chance of failure in the future. Wonder if anyone has done that and how it is working for you. Also can anyone post a picture or a diagram of the throttle body, I would like to be sure I'm playing with the wright hoses. Thanks for any replies.

PS: Did you cap off the open tubes on the throttle body after installing the bypass or is it safe to leave them open. I'm thinking of leaving them open, the reasoning being that if capped there could be water condensing inside after a drive and ultimately corroding something. Leaving them open would also help in heat transfer, keeping everything cooler.

Mr. Lucky

Well-known member
Aug 30, 2004
Orange, CA
2004 MY stroker Coupe
The throttle body bypass "mod" is a myth - don't waste your time. The reason the hose is there, circulating warm coolant through the tb, is to negate the possibility of the blade jamming due to condensation icing. Obviously, this is not a concern for you in SD. As for the bypass being a performance mod, it's flawed thinking. Since the original purpose is to heat the tb blade, and since cool air = denser air, which equates to more combustion power, the thinking is that bypassing it must offer more power. The problem with that theory is that the original function heats by by hot liquid coming in direct contact with metal (fairly efficient and immediate). The cooling theory depends upon cooling by high-velocity airflow through a warm cylinder. The problem with that theory is that the moving air is not in the tb long enough to be influenced by the surrounding temperature (few ms at most).

The only legitimate reason I can think of for performing this "mod" in a mild climate car is for ease of throttle body maintenance. There's no denying that it makes a mechanic's life easier by not having to deal with an extra hose containing fluid. If you want to do it for that reason, it's probbaly not a bad idea. While you're there, you could take the opportunity to remove and clean the throttle body blade and opening, and tip/shake out any coolant lingering inside, and then cap it off. Cleaning the throttle body, especially if it hasn't been done in a long time, may even improve your throttle response and/or cold idle.


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