# What's the point of coolant running through the throttle body?



## Nick2002GLI (Dec 23, 2008)

What are the pro's and con's of removing the coolant lines from the throttle body and bypassing them?


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## One Gray GLI (Apr 2, 2007)

*Re: What's the point of coolant running through the throttle body? (Nick2002GLI)*

no answer.
but ill chime in and say mine were bypassed.


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## BakBer (Apr 19, 2007)

*FV-QR*


_Quote, originally posted by *Nick2002GLI* »_What are the pro's and con's of removing the coolant lines from the throttle body and bypassing them? 


It is used for heating the throttle body. Keeping the throttle body warm prevents moisture from freezing during the winter. So I guess this helps in Canada... Last time I removed my throttle body I bypassed it.


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## apstguy (Apr 3, 2006)

Prevents the throttle body from freezing. If it never gets to freezing where you live, it is safe to remove it.


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## jefswat (Jun 10, 2008)

*Re: (apstguy)*

So does that have anything to do with why some cars don't behave well before they have reached operating temp in the winter?


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## apstguy (Apr 3, 2006)

I don't think so. What do you mean by "behave well"? Mine ran fine in Yosemite earlier this year at 18 degrees F. These engines do seem tempermental about outside temp though, it feels like I lose 20hp every time it is above 78F outside. It drops colder at night and suddenly I have more horsepower.


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## jediv6 (Oct 19, 2006)

Mine feels the same, on warm days seems lacking in power, but on cold days, goes like a rocket, whats that all about?


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## jefswat (Jun 10, 2008)

*Re: (apstguy)*

i mean when its below 0 cold


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## G_Lader_91 (Dec 28, 2006)

*Re: (jefswat)*

This is an interesting topic. My father told me not to mess with it because ice cold potentially form in there over time when driving in cold conditions. 
But I only travel north once a year and live in HELL (southern Ga.) so I definitely bypassed mine for now, and have encountered zero problems.

Oh yeah and amen on the running like a dog when its warm out. Oh but when its cold out.....


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## tungub (Apr 7, 2007)

*Re: (coatofarms)*

What's the benefit of bypassing it? I'm guessing in theory you're not warming the intake air, but has anyone dynoed it?


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## Nick2002GLI (Dec 23, 2008)

*Re: (tungub)*

SO how can I bypass it? I am really considering this. I have cld air intake..... It defeats the point of having c.a. Intake If the throttle body is hot.


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## apstguy (Apr 3, 2006)

Just cap the lines or stick a brass ball valve on one of them so if you go where it is cold, just turn a lever and it is heated once again.


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

Won't tht I terupt the main flow of coolant or these r secondary flow lines?


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## VEE-DUBBER (Nov 22, 2000)

*Re: (jediv6)*


_Quote, originally posted by *jediv6* »_Mine feels the same, on warm days seems lacking in power, but on cold days, goes like a rocket, whats that all about?

cold air is more dense than hot air. the more air/fuel (correct ratio) you can cram into the cylinder the more power you make. that's how forced induction works. forcing air into the motor. and getting too hot increases knock and detonation, and the ignition timing will retard and you lose power. with no knock or detonation you won't pull timing. (intake temp sensor reading too warm can pull timing too) hence using a intercooler and water/methanol injection on a forced induction car. 
how to make power 101
oh, and delete the coolant lines. that was a factory mistake.


_Modified by VEE-DUBBER at 12:35 AM 7-13-2009_


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## apstguy (Apr 3, 2006)

They are not critical to coolant flow, they are much to small to effect the main cooling system.
You should NOT just delete them if it EVER gets near freezing where you live or drive as your throttle valve could ice shut. All modern vehicles run coolant through the throttle body, VW is no different. This is no "factory mistake". There is always a reason behind the madness.
This engine seems more temperature temperamental than any other car I have ever driven. Small changes in temperature drastically changes the way the engine behaves. Typical VW quirk










_Modified by apstguy at 2:08 AM 7-13-2009_


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## koko5869 (Feb 15, 2006)

*Re: (apstguy)*

mine are gone. live in NEPA. know a lot of people who have gotten rid of them in the PA/NJ area, never heard anyone having any problems.


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## Nick2002GLI (Dec 23, 2008)

*I bypassed my throttle body coolant line and my CHECK ENGINE light turned off..*

WEIRD... I used to have the O2 sensor bank 1 code coming up....


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## apstguy (Apr 3, 2006)

When the cat starts to go bad the O2 codes will randomly go away and then come back. My light turned off for several months, but a couple weeks ago has been on pretty consistently again. I don't see any reason why it would CAUSE the light to go off. False association here.


_Modified by apstguy at 10:26 PM 7-13-2009_


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

my car doesn't have a single symptom of a bad O2 sensor. i get good gas mileage. 330 full tank. My car runs smoother than ever. And i've had that code for about a year and half. no 2 years.


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

these past 2 years i NEVER had a single sign of a bad a cat or 02 sensor


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## apstguy (Apr 3, 2006)

*Re: (Nick2002GLI)*

That doesn't make sense, you say you haven't had the code in two years but the TB bypass cleared it? You need to clarify.


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

HaD the code on for 2 years. Did te tb bypass today. No code..... Over the two years I had th code. My car never showed any symptoms or signs of a bad sensor or a bad cat conv. It runs smooth..... Great gas mileage.... Everytime I would put in a fuel treatmeant back in the day the light would turn off... Turn back on a moth later....


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## apstguy (Apr 3, 2006)

My car shows no symptoms of a bad cat but the constant O2 codes. A failing cat will show no symptoms but failing an emissions test or the O2 codes you are currently getting. Every once and a while the might smell like rotten eggs when failing, but more modern cars don't do that often.
Also, if the rear oxygen sensor goes bad, there will be no telling except for the MIL. The rear sensor only tells the ECU that the cat is working. and controls nothing on the car.
Your code will be back, just a matter of time.
Have you ever performed oxygen sensor aging tests? How was your last emissions test (if you have them where you live)?


_Modified by apstguy at 12:01 AM 7-14-2009_


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

I am confused... U think it's the cat or a sensor? I never had any smells... Mine is a 2002 gli. My code showed sensor bank 1.


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## apstguy (Apr 3, 2006)

It could be either. The code are indicative of one or the other.
http://wiki.ross-tech.com/inde...01056


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## jreed1337 (Jun 30, 2009)

*Re: (apstguy)*

what is the benfit of bypassing the lines though?


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## apstguy (Apr 3, 2006)

Cooler throttle body = cooler intake air. Cooler intake air = more power.


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## tungub (Apr 7, 2007)

I'm still curious if anyone has dynoed this. I could easily be wrong, but my guess is that the air is passing through the throttle body with enough velocity that there isn't much opportunity to heat the air. Not to mention that there isn't much surface area to the throttle body.
robert


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## koko5869 (Feb 15, 2006)

*Re: (tungub)*


_Quote, originally posted by *tungub* »_I'm still curious if anyone has dynoed this. I could easily be wrong, but my guess is that the air is passing through the throttle body with enough velocity that there isn't much opportunity to heat the air. Not to mention that there isn't much surface area to the throttle body.
robert

there isnt really much airflow. its not as its under vacuum or anything. just kind of a dead zone. 
with the coolant lines, one is supply and one is return, so its constantly moving. not so much with air.


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## apstguy (Apr 3, 2006)

I doubt it would be worth the dyno visit. I bet it is so minuscule I doubt it would even show up as anything other than the acceptable error rate.


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

Before the bypass. After my engin would get hot. I always noticed a decrease in torque. Especially on highways now it's consistent... And no reduction in power.... 4 dollars for the plastic 3/8 connector and the 2 caps to cap off the open ends and 5 minutes to bypass it... So it was worth my time..... Cuz when engine is hot the throttle body gets extremely hot and the air goes through that hot atmosphere and it DOES heat up. Cuz coolant flowing through there goes over 200 degrees..... Much more. Now after a 25 minute drive. I touch the throttle body, it's warm only. And the coolant hose is hellla hot!!


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## Nick2002GLI (Dec 23, 2008)

*Re: (Nick2002GLI)*

In the winter it will be torquey much more. Cuz it'd be more torquy with the tb not bypassed. In Vancouver wa it gets to about 35-45 at nght and 40-50 During the day so not enough to freeze it over, and improves how efficient the engine works.


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## apstguy (Apr 3, 2006)

You started the thread because you didn't know the effects of a TB bypass and now you are the expert? I think you need to give it some time before proclaiming victory.


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## Nick2002GLI (Dec 23, 2008)

*Re: (apstguy)*

I posted this before I bypassed it. Once I did bypass it noticed a significant difference! Ya racing wise itwont be noticeable but driving calmly it's noticeable. How the car responds. Becuz I don't abuse my car whatsoever.


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## eld101 (Apr 22, 2008)

*Re: (Nick2002GLI)*

Would I be better off removing these lines and capping them, or using a coupler and reconnecting them with the throttle body "out of the loop"?


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## apstguy (Apr 3, 2006)

I would say cap them, less to leak and break.


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## G_Lader_91 (Dec 28, 2006)

*Re: (apstguy)*

I bypassed my t/b. I noticed, and call me crazy that the car takes a little bit longer to warm up from a stand still. I agree with the t/b being alot cooler to the touch. especially after long drives. Not necessarily highway either. Weird eh?


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## mcdbones (Mar 14, 2013)

*Instructions on how to bypass*

The plastic T-valve connector from throttle body coolant hose and the T-valve to the heater hose have broken. It's going to cost me $156.00 for parts (dealer) plus $109 coolant flush & $92 labor(not dealer). After reading this thread I'm thinking I don't really need to fix this. 
How would I do this bypass? 

In the first image the T-valve to throttle body hose is broken completely and would need to find way to join remaining two hoses.










In the second image the T-valve to heater hose is only broken at small tip where the throttle body hoses attach.









Can any one please help? My car is nickel & diming me to death


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## turbo4motion (Jun 12, 2007)

Just buy brass barb fittings. Most hydraulic hose shops sell them. They should only be a few dollars each, and won't rust or crack. 
Like this:


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## Brett VR6 (Jan 29, 2008)

Hate to bring this back from the dead but I figured I'd throw my .02 in. I'm big into B-bodies, I'll always love them and they will always be my first love, anyway on the 94-96 LT1 powered cars it was almost a mandatory mod to do along with the first base and home plate delete (i.e. resonators). Well I forget who it was on the impala forum got his car dyno'ed before and after but I believe it was worth a 7-10 whp increase. Now I know on our cars with the smaller displacement the numbers will be less but its definitely a worthwhile mod. I haven't done my VR yet simply because I'm waiting to do my coolant system at the same time but it will be done. Any heat in the intake tract will kill power, the TB is no exception especially with how fast air transfers heat.

-Brett-:beer:


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## Honda Odyssey (11 mo ago)

apstguy said:


> They are not critical to coolant flow, they are much to small to effect the main cooling system.
> You should NOT just delete them if it EVER gets near freezing where you live or drive as your throttle valve could ice shut. All modern vehicles run coolant through the throttle body, VW is no different. This is no "factory mistake". There is always a reason behind the madness.
> This engine seems more temperature temperamental than any other car I have ever driven. Small changes in temperature drastically changes the way the engine behaves. Typical VW quirk
> 
> ...


Well if u know that coolant have charge and it's also reverse in polarity by the way that's why some of the parts related to the throttle body rust its because rust it come from oxigen and oxigen its - charge atract to positive charge in the coolant since that I mentioned in first want coolant cross the negative field that runs the block , became coolant became positive, now why its that happening its because the cold air its more boost end u see more power if you delete that coolant from the throttle body now will atract to + air and its 73 % nitrogen that's why cold air its more power the more cold it gets more power the more hot I gets loss power why its that . When its cold contract/vx hot expend and when expend loses pressure because of heat and heat its be cause oxigen , that's why when u forging metal the furnace need lots oxigen into to get hot, we don't want to the engine to be hot , will lose power, cold its the way


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