TB Coolant Crossover/Bypass, Any Disadvantages?
 

How many have done this?

Throttle Body Heat Bypass Line by Marc Haibeck

Possible reasons to bypass the throttle body?

1) Much "stuff" is under the plenum (starter, A/C compressor, coils, etc). If bypassed, you don't have to fuss with draining coolant and refilling it (and getting the air out of the system). Bypassing, or even plugging the passages off entirely, eliminates both PIA parts associated with coolant draining. With an air ratchet, one can have the plenum off in about 5 minutes (if you leave the throttle lines connected), and on again in a few more (depending on condition of the gaskets). Fussing with coolant can easily add an hour to that process, has been my experience.

2) The plenum runs cooler which better for performance. Marc Haibeck has run his ZR-1 in the Chicago area for years and in sub freezing temperatures w/o any problem with icing.

3) Corrosion can be an issue with coolant running through the plenum.

Re: TB coolant crossover,any disadvantages?
 

I have the by-pass and no problems. I don't have to worry about any leaks at the TB.

Re: TB coolant crossover,any disadvantages?
 

One disadvantage is if you don't flare the ends of the bypass pipe, and the rubber line slips off and streams coolant under your plenum killing your starter. Ask me how I know about that one?

Re: TB coolant crossover,any disadvantages?
 

I have, no issues on my DD in AZ heat either

Re: TB coolant crossover,any disadvantages?
 

I bypassed both the throttle body and the entire plenum, no regrets. I did a write up on it for HOTB - last year I think?

Re: TB coolant crossover,any disadvantages?
 

Yep! I didn't have the bypass though. The stock hose ruptured, facing towards the plenum (of course) & flooded the valley. Stuck in a gas station, fixed it, starter toast but easily push started (small miracle).

Lesson: don't forget the "little" coolant hoses when you replace the "big" ones.

Re: TB coolant crossover,any disadvantages?
 

Thanks for the replies.The reason I want to do this is to save the paint on the TB.

Re: TB coolant crossover,any disadvantages?
 

Anybody got some pictures of this mod?I broke out the tube cutter,bender,flaring tool and then ran into a wall.The plan was to make a hard line and run it under the front of the plenum keeping the coolant line intact,no room wont work.Next plan was to plug the line on both sides of the TB with the lines intact keeping the look stock.My question is the small line coming off the TB going back into the plenum,is this for a return back into the system only?Ive even thought about removing the TB plate and filling the cavity with epoxy to seal out the coolant,thats a bit drastic.

Re: TB coolant crossover,any disadvantages?
 

http://zr1specialist.com/HAT%20Web/p...t%20bypass.htm

Is this what you're looking for?

Re: TB coolant crossover,any disadvantages?
 

Thats it,I was all set to make one of these but couldnt see any room under the plenum.Now I know it can work Ill go take another look,Thanks for the link.

Re: TB coolant crossover,any disadvantages?
 

after i did this mod .i took 2 3 ft sections of hose and ran 1 to the front air dam and the other tothe right side wheel well so that cool air can circulate thru the throttle body, dont really know if it helped ,but figured it couldnt hurt

Re: TB coolant crossover,any disadvantages?
 

Coolest thing you could do for your throttle body is to install one of the Billet trottle body plates :mrgreen:

Re: TB coolant crossover,any disadvantages?
 

Yep, I love mine...thanks Carter!!!
Rich

Re: TB coolant crossover,any disadvantages?
 

Rich,
Glad I could help :cheers:

Re: TB coolant crossover,any disadvantages?
 

May I ask what type of hose you guys use as replacement hose for the coolant lines along the plenum? I know I can get 3/16" fuel hose, but I'm not sure that is okay for this situation.

TIA
:cheers:
Tom

Re: TB coolant crossover,any disadvantages?
 

You should be able to buy heater hose that is that size. I suspect fuel hose would work too, though?

Re: TB coolant crossover,any disadvantages?
 

Thanks Bob:thumbsup:.....sometimes it's the simple things that escape my eye!

Re: TB coolant crossover,any disadvantages?
 

I used fuel hose on mine................

Re: TB coolant crossover,any disadvantages?
 

Got the job done,what a pain in the a$$.Despite the fact that this pipe was supposed to go in with out removing the plenum,that wasnt the case.There was no way in hell this was going in without at least raising the front of the plenum.Then I had to take my tube bender and change the pipe quite a bit on the driver side.Once I got the plenum up I could see oil residue everywhere so I went ahead and removed the plenum to clean everything up.While I had everything apart I found the secondary solenoid wasnt holding vacuum.In the past the pump would evacuate the system and cycle one second every 7 seconds then it got down to about 4 seconds.Replaced the solenoid no it holds vacuum for maybe 30 seconds or longer.The cars got a stumble if you stab the pedal off idle.Found a vacuum leak at the PCV fittings so Im working on that now.I ran a preformed hose off of the TB nipple to give it a finished look.[IMG]http://i10.photobucket.com/albums/a1...M/DSCN0349.jpg[/IMG][IMG]http://i10.photobucket.com/albums/a1...M/DSCN0356.jpg[/IMG]

Re: TB coolant crossover,any disadvantages?
 

Heres the pipe after I flared the ends.I figure for $30 Ill make one before I put this in the car.[IMG]http://i10.photobucket.com/albums/a1...M/DSCN0333.jpg[/IMG]

Re: TB coolant crossover,any disadvantages?
 

Bob's ( Locobob ) write up is in an issue of our newsletter. I forget which one...:o...but I'd guess in maybe the 07 issues. He blocked the water flow to the plenum from the I/H's.

:cheers:
Tom

Re: TB coolant crossover,any disadvantages?
 

The 2 hoses on the TB nipples are connected to nothing,this looks better than 2 caps on the TB.I dont know if there is enough room to run a hose under the plenum but more importantly if the hose leaks,it could spray everything under the plenum.You could run a hard line or a hose around the front under the air horn.

Re: TB coolant crossover,any disadvantages?
 

Have Locobobs mod on mine. Running a year now with no issues. Cleans up all the plumbing and I can pop my plenum off any time with out dropping coolant. Here is the right side of my motor... much cleaner without the hoses. Just thead the hole in the injector housings and install a plug. Very simple and clean.
H
:cheers:

http://i249.photobucket.com/albums/g...e/IMGP2402.jpg

Re: TB coolant crossover,any disadvantages?
 

Just to be clear, when I say "thread the hole in the injector housing" I'm refering to removing the plenum, and pluging the coolant passage in the top of the injector housing where it meets the plenum, with a threaded stainless plug, on both sides. This will stop flow of hot coolant to the entire plenum and throttle body area. As in the attached photo.
H
:cheers:

http://i249.photobucket.com/albums/g...oolantPlug.jpg

Re: TB coolant crossover,any disadvantages?
 

The brass plugs were only an expediant, you'll note they are wraped in teflon tape for the very reason you point out. I want to change them out for stainless flush fitting plugs, just haven't gotten to it yet.

As for the coolant in the injector housings, there really is none other than the passage to get the coolant through to the plenum and more importantly to the throttle body. The purpose was to prevent "Iceing" in very cold driving conditions. I never drive my car in winter conditions, so it's not an issue.

BTW the coolant bypass hose that runs from the right side of the engine to the expansion tank is simply capped off at the tank.

Hope that helps.
H
:cheers:

Re: TB coolant crossover,any disadvantages?
 

I was going to cap the coolant and eliminate the plenum all together but was told there were issues dealing with steam in the top end that needed to move back to the system.Several have eliminated the coolant in the plenum with no problem so I guess it all depends who you talk to.

Re: TB coolant crossover,any disadvantages?
 

No, the entire coolant flow for each bank of the engine goes out the coolant pipes on the side of the injector housings and then to the radiator/bypass.

To me, if anything is stagnant, it would be the original TB coolant system. Coolant pressure should be identical on both banks, coming up from the cylinder heads. If pressure is identical or near identical, flow would be minimal at best through the TB coolant system. Probably more of a thermal transfer system rather than flow in the normal sense.

Re: TB coolant crossover,any disadvantages?
 

It would be a good idea to purge the plenum of coolant when you do the bypass.

I do not think any residual coolant is going to turn to steam as the plenum has so much ambient air moving through it, the intake is the coolest part of the engine. Never measured it but I doubt it gets hot enough to boil water/steam.

Re: TB coolant crossover,any disadvantages?
 

What size tap and plug did you use?

Re: TB coolant crossover,any disadvantages?
 

Cliff,

You want Heart of the Beast, Issue #10, April 2007, pages 7-10.

Robert's (Locobob) write up is the bomb and will guide you step by step. It works awesome and never looked back. You don't have to worry about the under the plenum deal and leaks, but some folks will not like the plumbing on the top end so check it out.

Re: TB coolant crossover,any disadvantages?
 

It appears that there are six threaded plugs we are talking about to eliminate ALL the hoses (including coolant bypass hose) all the way back to tank. Four on the plenum and two on injector housings. They all look like 1/8 inch pipe thread to me....is that correct? I assume you simply cut off the existing hose fitting and drill the remainder of the fitting out of the plenum tapping with 1/8 inch pipe tap.

photos provided by Ccmano
http://i287.photobucket.com/albums/l...assplugged.jpghttp://i287.photobucket.com/albums/l...oolantplug.jpg

Simply cap off the bypass hose at the tank as Ccmano says eliminating that TB bypass hose going from "T" on passenger side of engine to tank also.

Re: TB coolant crossover,any disadvantages?
 

Would it be better to use aluminum pipe plugs instead of brass or stainless?

Re: TB coolant crossover,any disadvantages?
 

So, old thread. When i replace my plenum, can I remove the pressed in fittings and eliminate those lines?

Re: TB coolant crossover,any disadvantages?
 

Yes, you can. If you wanted to take it one step further, you should plug the water passage in the injector housing before it enters the plenum. This will eliminate the need to drain the coolant down to do any future plenum pulls.
Rich

Re: TB coolant crossover,any disadvantages?
 

See Item #4 LT5 Eliminated Systems

As Scrrem shows above The associated two IH coolant ports in the IH should also be plugged on each side.

Photo by Ccmano
http://i287.photobucket.com/albums/l...55797df488.jpg

Total six coolant ports plugged One each side TB, One each side Plenum, One each side Injector Housing.

See (Filling With Coolant and the Air Locked Water Pump) for Detailed New Coolant Filling Trick.

You do not have to wait over night Hoping you heated the water pump area up enough to draw coolant into the area of the water pump impeller by running without coolant flow the night before. I used this proceedure to make sure I did not have an Air Locked Water Pump which has nothing to do with TB Coolant Blocked since this proceedure was used before I ever blocked my TB Coolant ;)

http://i287.photobucket.com/albums/l...enumblockN.jpg

Remove TB Coolant hose and tubing left and right side of plenum and plug hose return to coolant tank passenger side See Brass Cap just above the "T" On Passenger Side. Initial Coolant Fill may be somewhat affected by the TB Coolant Elimination (see item #4 Initial Coolant Fill). The "T" connects the top of the radiator Air Vent, TB Coolant Return, and Coolant Reservoir in front of Passenger side. With the TB Coolant Return Blocked, what is left is a coolant line from the Radiator Air Vent to the Passenger Side Coolant Reservoir.

http://i287.photobucket.com/albums/l...666a77e43d.jpg

1990 LT5 with TB Coolant Eliminated
http://i287.photobucket.com/albums/l...b1ba5026d5.jpg

1991 LT5 with TB Coolant Eliminated
http://i287.photobucket.com/albums/l...510aaf14f2.jpg

Re: TB coolant crossover,any disadvantages?
 

What are the down sides to this? Other than the freezing issues I've read about.
Drill, tap and plug the holes? -Steve

Re: TB coolant crossover,any disadvantages?
 

None :p

Marc has found that the throttle body (TB Coolant Blocked) has no problem with ice when the ambient temperature is at 20 degrees and the humidity is 90% :cheers:

As discussed in......Throttle Body Heat Bypass Line

I do not use a Bypass Line on either a 1990 and a 1991 with NO issues.

Re: TB coolant crossover,any disadvantages?
 

So just yank the lines and plug the holes?

Re: TB coolant crossover,any disadvantages?
 

Do not "yank the lines" but rather remove the fittings carefully so you do not break them off making that removal more difficult.

Actually the cause of the Air Locked Water Pump is not related but a Coolant Refill Proceedure that has worked every time for me for the Air Locked Water Pump has been defined. This applies if in fact you drained ALL your coolant at a level BELOW the Water Pump (TB Coolant Bypass blocked or not).

See (Filling With Coolant and the Air Locked Water Pump) for Detailed New Coolant Filling Trick.

You do not have to wait over night Hoping you heated the water pump area up enough to draw coolant into the area of the water pump impeller by running without coolant flow the night before. I used this proceedure to make sure I did not have an Air Locked Water Pump which has nothing to do with TB Coolant Blocked since this proceedure was used before I ever blocked my TB Coolant ;)

Marc has installed the TB Heat Bypass Line as a precaution for those he is not sure about their "do it yourself" skills in dealing with coolant issues.

But you have to confer with Marc on the need for the TB Heat Bypass :p

Re: TB coolant crossover,any disadvantages?
 

Major thanks Dyno. I'll go through all the finer details when I have a chance, like reading up in the (your) solutions.

Scrrem, what did you use for plugs?