I make it a practice to remove the coolant lines to the throttle body wherever possible. This makes servicing an easier task and removes the potential for water leaks anywhere on these lines. I have three years on the road using this method and have experienced no ill effects. I came across this article on a GM website and it seems to echo my sentiment so I thought that I'd post it here.

Throttle Body Coolant Bypass
By sappyse107

This isn't so much a myth, as it is exaggerated. The lines were put in by GM for cold climate conditions, which is said to cause ice to form on TB, which could cause a lot of problems, like a stuck open condition that can cause an accident. There have been no known reports of this happening, but there hasn't been any research either. (unless you want to considerer my road experience over time-DL)

The idea behind removing it has nothing to do with the ice though, it is removed to keep the hotter coolant from heating up the TB. Cold air is good for a motor's performance, but the air moves so fast that the TB temp isn't really going to make a difference. Cooling the TB and Intake manifolds will help however.

The real gain from this mod is to eliminate one area that "can" leak, and if you tear the motor apart at all, those coolant lines can be a pain to remove when you want to remove the TB or the plenum. Because this is a really cheap modification, it is still recommeneded to remove the lines if you don't have to worry about ice forming on the intake (only because it would be bad to recommend something that could be potentially dangerous). Every little bit helps when cooling the intake, just don't think you will notice anything from it. Not only will you not notice anything, you won't get anything on a dyno because of it either (on its own).

I agree with removing the coolant lines to the throttle body. I have a V8 and have had them removed for about 3 years with no change in starting operation or performance. Also the engine compartment looks cleaner without the hoses routed all around to the inlet and outlet of the T.B.

Whats funny is there's people trying to make money off this. There's "bypass kits" all over eBay they're trying to hock for like 8 bucks or something. Soon as I saw that, I just took the lines off and plugged the holes. One of my cheapest mods ever, though not the easiest, cause you have to pretty much take the upper plenum off to get the stupid lines out.

I have removed mine as well without any problems. But I don't use my Fiero during winter here in Sweden

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1985 Fiero Twin Turbo
http://www.dtek.chalmers.se/~d99hb

quote Originally posted by Dennis LaGrua: Throttle Body Coolant Bypass By sappyse107

I'll be doing this mod on my Fiero as time allows; I've driven my Beretta with the TB coolant lines bypassed in all seasons for about 70,000 miles, with no ill effects whatsoever. It sure makes it easier to remove the TB for cleaning, etc....

By the way, Ben (sappyse107) is also one of the guys at Fast Forward Performance, a company that makes underdrive pullies, poly mounts, custom chips, and the like for the GM FWD market. He's a good guy!

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I've always removed them also.

I've driven my 86 thur two winters with it bypassed and no problems. I recently decided to upgrade my ignition and when pulling out the distributor those stupid lines were in my way....I removed them (most of them) with my hacksaw....they're just in the way, that's about the only purpose they serve in my book.

The only downside is that theres a black box that mounts to the lines on the left side of the plenum, so when you ditch them, its just kind of hanging there.

I bypassed those lines on the Cutlass.... I felt a "minor" increase for the better.....

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Disconnected mine a while ago and when I put a turbo on my engine the coolant lines are feed from there. It use made it easy to cool the turbo, one of the few things that was easy with my DIY turbo install.

put doesent the erg put hot exhast in behind the throttle body. I would quess that the exhast gas is hotter then the coolent. wouldent then when the erg is working that the coolent cool down the throttle body?

quote Originally posted by Fastback 86: The only downside is that theres a black box that mounts to the lines on the left side of the plenum, so when you ditch them, its just kind of hanging there.

I used a dremel and cut the flange off of the pipes. Then Painted it balck and stuck it back on.

I live in an area that has DEQ(emissions) testing. I have heard that this change causes problems with passing emissions testing to do the fact that the ECM looks at both coolant(engine) temp and air intake temp.

Myth or not. Anyone with experience in this matter would be appreciated.

The intake air temp sensor is in the air box with the filter. Changes in air temp going through the throttle body don't affect it.

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'87 Fiero GT: Low, Sleek, Fast, and Loud
'90 Pontiac 6000 SE AWD: None of the Above

Luck, Fate and Destiny are words used by those who lack the courage to define their own future

... what fieros are these coolant lines on? i have an 85gt that has no sign of coolant lines on it? where are they?

my '84 4 cyl has em, going from the rear wall of engine compartment to the intake manifold

Consider this: I'm in San Jose and it's almost 10:00 PM. It's 62 degrees F outside right now. However, the relative humidity is 68% so the dew point is 51 degrees F right now.

As the air rushes through the throttle body, a low pressure area forms behind the throttle plate. As the air pressure drops, so does its temperature. Down to the dew point? You bet. Down enough to form frost? Probably not - but I"d just as soon have a little extra heat around the throttle plate just to make sure.

The problem that throttle body heat solves is the one where frost forms around the throttle plate while you're driving down the road - when you try to slow down the throttle is stuck (frozen) open. Yes, this can and does happen - and it can happen even in a warm weather climate like San Jose.

If you just run around town and do a little street racing you can disconnect the coolant lines to the TB. It won't gain you any performance but it'll look cleaner under the decklid. But if your driving includes highway cruising on cool summer evenings you really should leave those coolant lines hooked up. A stuck throttle is no fun...

I disconnected the heat on a carbed Fiat X 1/9. Then that fall I was driving along about eight miles from home when the mist came out, thiry five degrees with thirty five degree dewpoint. I was kinda lucky it was a carb, the orifice the gas dribbled out of would ice up first and the engine would stop. Then after about ten minutes of enjoying that misty thirty five degrees the engine heat melts the ice off and I go just as fast as the Fiero can go for a whole ninety seconds. My average speed ended up about four miles an hour, took over two hours to go eight miles.
If the Fiat had been port injected, yep, I'da backed off and by the time the realization of stuck throttle sank in I'da had no time at all. Bang, ouch.

Yeah yeah, one time in a lifetime of driving {52}, and I can watch weather, and its not like its an airplane and I'll crash on takeoff, but still the heat stays on.

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Good point Whuffo, but I would think that the relative temperature of the engine, which gets translated into everything in thermal contact with it, Throttle Body included, would prevent icing in the TB. If nothing else, its not exactly cool in the engine bay. I'm no master mechanic, but I would think it would be hard to get it cold enough for ice to form in the TB once the engine is warmed up.

A lot of pilots have thought the same thing...it's a warm day, yada, yada...there are old pilots, and there are bold pilots, but there are no old, bold pilots. GM is chintzy...maybe the TB heat won't ever perform its function, because the conditions have to be just right for the icing to occur...but you can bet that if the GM bean counters felt including it was necessary to avoid product liability lawsuits, then at some point they decided it was more than just a remote possibility, especially since the failure mode involves a throttle stuck in the open position. Do you suppose the issue might have come up in testing?

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88 Formula, "Asphalt Aviator"

For those who understand, no explanation is necessary, for those who do not, none will suffice...

I always disconnect them as well. It can do nothing but help performance. Hot water going thru the TB increases fuel mileage and hurt performance. I disconnect mine under the thermostat housing. The two lines connect by way of a rubber hose. I just disconnect the hoses and make a loop with the supply hose so that it goes back into the engine. This will not increase HP noticibly, but alot of little increases makes for a bigger increase.

Phil

quote Originally posted by GTDude: I always disconnect them as well. It can do nothing but help performance. Hot water going thru the TB increases fuel mileage and hurt performance. I disconnect mine under the thermostat housing. The two lines connect by way of a rubber hose. I just disconnect the hoses and make a loop with the supply hose so that it goes back into the engine. This will not increase HP noticibly, but alot of little increases makes for a bigger increase. Phil

The amount of heat that this system puts into the intake air is trivial. Its sole purpose is to heat the 1/2" of area at the very bottom of the throttle body where the throttle plate is located. It only heats it enough to prevent any possible ice formation. Removing this system will have absolutely no effect on performance, one way or the other.

You can be assured that lawyers will have no problem discovering the removal of this system should a stuck throttle from ice cause an injury accident. The fact that this system was disabled by the driver would absolve the insurance company of any liability, so the driver will be paying attourney fees and settlement costs out of their own pocket.

Ouch.

Ever heard the phrase "It's cheaper to keep her"?

JazzMan

Bolt cutters are very good for removing the lines without removing
the upper plenum.

If it ever does stick I can always pop it into neutral and shut it down
(as in turn the key to the off position). Coast to the nearest safe place to
stop. Doubtful that ever happens.

Only has to happen once.

JazzMan

Good point......I removed them already.

If I crash I'll be sure to let you all know and
you can say "I told you so".

LOL

quote Originally posted by JazzMan: The amount of heat that this system puts into the intake air is trivial. Its sole purpose is to heat the 1/2" of area at the very bottom of the throttle body where the throttle plate is located. It only heats it enough to prevent any possible ice formation. Removing this system will have absolutely no effect on performance, one way or the other. You can be assured that lawyers will have no problem discovering the removal of this system should a stuck throttle from ice cause an injury accident.

Hear hear!!

The amount of time that the intake air spends in the throttle body is miniscule. Sure... Physics dictates that it must absorb some non-zero amount of heat as it passes by, but compare this to the length of the long run of the upper and lower intake plenums combined... The two inches of "water fed through a tube" warmed throttle body contributes absolutely nothing when compared to the ten inches of bolted directly to the engine block plenum combination! C'mon people!!

Let me add one more thought to this mix...

The only time you even CARE about any of this is when you are at wide open throttle!

Why?

Because if you are looking for more power, push the gas pedal down further. You'll get more power. It's a time honored tested true method. The only time this method fails is when there just isn't any more pedal to be had. In other words, the pedal is on the floor and you still wish you had more power.

Now... If you think the air going through the throttle body moves fast at idle, then just IMAGINE how fast it's rushing through there at WOT!!

Flame suit on, but anyone who thinks this change matters a hoot for performance doesn't have a firm grasp on thermodynamics. If you still have doubts, then simply stick thermocouples before and aft of the throttle body and measure the differential. Squat...

-Bruce at FTF Engineering

I had an Alpine Renault with a high-strung 1300cc motor with dual side-draft Webers. Very pretty set-up -- but suffered terribly from carb icing. A heat of July problem -- high humidity was the killer, not ambient temprature. Push it hard in hills & the carbs would ice up solid -- even though the temprature was 80 and over Fahrenheit. Was embarassing to sit on the shoulder and wait for the block heat to trickle up through the manifold and melt everything ...

I had to wrap the carbs with foil & capture some exhaust heat to keep the carbs clear ... or only push when the humidity dropped to zero -- as it always did when it got cold. Car ran like a dream in the chill of November, even when ambient was at or near freezing.

A little throttle body heat is a good thing, I think.

Cheers,
GB

Three very sound reasons for it's existance have been posted in the above thread:

A. If you disconnected it, You only have to have your throttle stick wide open one time, to realize why they designed it in !!! Hope you don't kill yourself or someone else.

B. It would be a real nice cost savings for the Auto Manufacturers to remove this feature, and Risk Management of all those Companies using the system will not allow them to remove it.

C. There isn't any measurable difference in hp, doesn't matter if it's hooked up or not.

Frankly, while I've never measured my throttle body temps, I believe the coolant lines actually keep it cooler than it would be if they were disconnected, there a lot of heat from the heads to intake and engine compartment going direct to that unit.

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0 to 75 Audio http://www.cartsys.com/fiero/cal-engine.wav

[This message has been edited by California Kid (edited 06-24-2004).]

Give your head a shake guys! Yeah, my TB is gonna ice up in a 200F engine bay.....holy crap...the sky is falling!

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Calgary - August 1, 2004 Fiero Fiesta
1984 Indy Fiero 3.4/3100 Hybrid NA and...
*ALL THROTTLE AND NO BOTTLE*
http://www.gmpcm.com/ Killer ECM/ PCM tuning software and information

quote Originally posted by donk316: Give your head a shake guys! Yeah, my TB is gonna ice up in a 200F engine bay.....holy crap...the sky is falling!

You my friend live in an area were it is probably most likely to happen, if the conditions are right.

quote Originally posted by California Kid: You my friend live in an area were it is probably most likely to happen, if the conditions are right.

Maybe someone who drives their car in the dead of winter, mine stays under covers from NOV- APRIL. Thanks for the concern though!

As said above, it does not have much to do with winter at all, mainly spring / fall, and sometimes in the middle of summer. In the winter time the air is mostly dryer containing very little water. But I can tell you just don't care enough to look into it and understand why it happens.

Then why after 15 years of building engines is this a big deal?

Motorcycles are an excellent example of the same idea. Do they have "throttle warmers?" no. Ive never heard of this at all.

Both my throttle bodies sit 8 inches above a 2" exhaust pipe. Im really not concerned.