Throttle Body Coolant lines

So my car was overheating the other day and I found that I had a coolant leak somewhere on top of my engine on the drivers side. I knew this because when I was searching with a flashlight I saw little pools of coolant in the casting ridges in the block. So of course I am like WTF? how is coolant leaking there???

I figured the best way to get a good look at what was going on was to take off the intake manifold. It was a minor pain, but not too bad. (That last little bolt on the bottom is a Subaru engineer saying "F*#k you"!! )

So I was able to trace the leak to a little coolant line feeding the Throttle Body. Again I say "WTF"?? I had NO idea coolant flowed through the throttle body. I used my level 10 googlefu skills and found out that it's hot coolant flowing to warm up the throttle body for cold weather (I guess so the butterfly valve does not stick). I also find out that some people do a bypass "mod".

So my question is this: Should I even think about doing this "mod" while I have everything apart?? Is there any benefit to this?? I live in So Cal so its pretty warm year round. I do go to Mammoth, Big Bear or other cold weather areas every now and then, but not often at all. The main benefit to this "mod" IMO is that doing it is quick and easy and I don't have to go buy parts and it's hopefully one less leak point in the future.

I also have very good access to the TVG's at the moment....Do I even think about taking them out?? I am not pushing big power nor do I plan to. It's more of a "While I am in there" type of things.

So what say you my fellow LGT'ers?

If you never expect to drive in any humid/cold weather conditions it's likely to be safe to bypass, but otherwise you should keep the heating since there's a risk that the butterfly can stick in an awkward position causing an uncontrollable engine. It's there to prevent ice to form in the throttle body, and many people that has been driving old carburetor cars has experienced trouble with this, but in those case it has usually been a stalled engine.

With a fuel injection system the conditions may be completely different and the engine may not stall but stick to high revs.

In SoCal, you should have zero issues.

I still would not do the bypass.

Put it back the way it is supposed to be.

Did you replace the o-rings with the bigger orange ones whe nyou had the intake of ?

Thanks for the input guys. ^^have not replaced any of the orange O-rings on the intake manifold or throttle body (car is still apart, waiting on a new starter to get it back all together.) Are there new updated parts or something?

Yes, where you live it may not be a big thing. But in the colder area's the OEM o-rings shrink when it's cold and you have idle issues.

The new orange o-rings are like $20.00 at the dealer and are twice as big as the 05's came with. The TB should be fine.


You should also tighten all the gas line clamps under the intake manifold while its off. Same type thing, when it's 20F the hoses can leak.

I did this throttle body coolant bypass mod on my '99rs. There was some data out there in the internetwebisphere that showed reduced intake air temps after performing the mod. Whether it made any noticeable difference in power.... meh?

I''ve been dailying the car with the bypass mod for over a year now. Its usually hot(90+) in Texas but it does dip down to the the high 20's/low 30's at night occasionally during "winter". I haven't had an issue yet and it deletes two potential coolant leak spots. If you have the right weather, do it.

There are no issues with bypassing the TB coolant lines in warm weather areas.