Plenum Coolant Hose Question

[msuhanek]

Afternoon all - Not sure if I explained this question properly but has anyone seen this type of setup on the LT5? See pic. The prior owner (a ZR1 Registry Member) bypassed both the vacuum(?) openings as you look at the front of the plenum. He took about a 2 foot rubber hose and connected them together on both sides. He said this would help the cooling of the engine especially in hot weather. Any help is appreciated. Thanks

[secondchance]

Afternoon all - Not sure if I explained this question properly but has anyone seen this type of setup on the LT5? See pic. The prior owner (a ZR1 Registry Member) bypassed both the vacuum(?) openings as you look at the front of the plenum. He took about a 2 foot rubber hose and connected them together on both sides. He said this would help the cooling of the engine especially in hot weather. Any help is appreciated. Thanks

Those are not vacuum ports but rather coolant line into plenum/throttle body. Looks like prior owner opted to bypass throttle body. This makes servicing under the plenum simpler since coolant doesn't have to be drained prior to removing the plenum.
No down side especially in warmer states.

[george1945]

Are there any other benefits to this or drawbacks?

[efnfast]

GM was concerned that the throttle body might frost up in cold weather. There is also concern that air pockets could form there and the lines might help move the air out.
I plugged the passages inside as opposed to running the line.
I would also think it would help keep the sir cooler as it's not running though a heated throttle body.

[secondchance]

Are there any other benefits to this or drawbacks?

In severely cold weather, I think, this set up prevents throttle body icing - at least I think that was the intent. I drive my Z even in winter months as long as roads are clean and dry. Even with TB coolant bypassed, I had no issues.

[efnfast]

I think the coldest mine has seen is 17 with the TB bypassed. No issues.

[Z51JEFF]

One drawback with the coolant running through the TB is it starts to corrode the aluminum around the TB plate opening. I've seen this routed around the back but never around the front. I've got the running under the plenum out of site.

[Dynomite]

Injector Housing TB Coolant Blocking (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-10.html#post1588695506)

1. You can Block TB Coolant at Injector Housing.
You can Block TB Coolant at Injector Housing without removing Injector Housings.
Recommend removing Two Injector Housing Coolant Manifolds to Block TB Coolant at Injector Housings.
You can then keep or eliminate the Plenum hoses/tube on passenger side or leave it in place.
No more hose clamps required on the TB Coolant Hoses to TB if you want to leave the stock look.
You do have to Block TB Coolant near Coolant Reservoir if you Block TB Coolant at Injector Housing.
2. You can also Bypass TB Coolant with the Coolant circulating through the Injector Housing/Plenum.

1990 LT5 with TB Coolant Blocked at Injector housing, ALL TB Coolant Hoses and Tube eliminated
http://i287.photobucket.com/albums/ll142/dynomite007/A%20Corvette%20LT5%2090/f1e67ee1-dca6-4b7e-b799-feb1ba5026d5.jpg

1990 LT5 with TB Coolant Blocked at Injector housing, ALL TB Coolant Hoses and Tube In Place
http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite10/63a572bd-1dd6-4143-b2f1-1b01bafe478a.jpg

[msuhanek]

Would bypassing the Coolant injector also increase the idle speed - my idle speed is generally in the 1000-1100 range on the tach. Thanks all!
:Eagle:

[secondchance]

Would bypassing the Coolant injector also increase the idle speed - my idle speed is generally in the 1000-1100 range on the tach. Thanks all!
:Eagle:

Not related. I suspect possible small vacuum leak causing higher idle.

[msuhanek]

Thanks Second - if small vacuum leak try looking at/replacing and tighting all the rubber hoses? Any more help greatly appreciated. Thanks
:flag:

[secondchance]

Thanks Second - if small vacuum leak try looking at/replacing and tighting all the rubber hoses? Any more help greatly appreciated. Thanks
:flag:

Next time you are servicing under the plenum I would start with a hand held vacuum pump. Attach to vacuum line starting close to vacuum pump and see if vacuum holds. Do the same on the driver side by the reservoir and vacuum servo for the cruise. Also, at vacuum port on the sides of the plenum - trial and error and isolate process.
Likely suspect is connections between rubber fittings and hard plastic lines under the plenum typically referred to as vacuum spider. It's most likely small amount of leak at multiple rubber/hard plastic joints. I would slide hard plastic line slightly off rubber fitting, dab of crazy glue, and slide it back in. Some use plastic zip tie as additional insurance. I use epoxy around the hard plastic line to rubber fitting joints as insurance.
New spider may solve the problem but after a few years, eventually rubber fitting will loose elasticity and end up with the same issue.