I've recently replaced my water pump and did some work under the plenum on my '90 ZR-1 and have since been working on sealing some coolant leaks that suddenly appeared. I was able to solve the first two leaks with a thicker plenum gasket and some sealant but fixing those two turned the third minor leak on the fitting that connects the plenum to the throttle body coolant hose in a major leak. In an attempt to seal the final leak I tried removing the fitting by rotating it back and forth but that resulted in the fitting snapping completely off, leaving the press fit part stuck in the plenum. If anyone has any advice on where to find a replacement fitting or how to get the press fit piece out of the plenum it would be much appreciated. Attached are a photo of the broken fitting and the corresponding part in the service manual(no gm part number was provided and I can't find one). I saw some other posts suggesting to plug the throttle body coolant hoses but I'm concerned about if that'll impact the engine in any way so info on that process would also be welcome. I also saw people suggesting to use an easy out or a drill to remove the press fit piece but if there's an easier way I'm all ears. Thank you for reading my post and thank you to those who respond.

 

That is unfortunate to see, but most of us have been there. A quality engine builder may be able to assist with extracting what is essentially a pressed in sleeve at this point.

Regarding plugging the coolant crossover: I have done this on my 91. The plenum itself has to come off, and the passageways in the injector housings are drilled and tapped for pipe plugs to thread in with sealant. The beauty of this upgrade is no longer needing to drain a gallon of coolant just to get into the valley. You will read tips and hints about just unbolting the reservoir tank and tipping it into a bucket and that solving the issues of draining coolant, but that advice was better served when the cars were newer. All my factory hoses attached to that tank are as hard as a rock. They would crack and leak if I tried to tip that thing into a bucket.

If you find a quality machine shop, or engine builder nearby, they can remove that snapped off piece, and install those plugs in the injector housings. Refilling the engine with coolant is not a problem with those passageways blocked. Marc Haibeck provides a tutorial on his website for the best way to burp an LT5. Jack on the frame under the passenger side mirror, and tilt the car as far up as it can, it’s that simple. Done it several times without issue. I’ve seen pics of guys that drilled and tapped bleeder valves into the tops of the coolant crossover tubes, and thought there’s no way it’s that hard to burp the coolant system.

 

Not sure if this is how I reply, this is my first time writing on the forum. I have an extra gasket set from Jerry's gaskets and it says on the product page that I can just flip the gasket around and it will block off the coolant ports, do you think that would work fine or do I absolutely need to take it to a machine shop(I'm short on both money and time so a quick/cheap fix would be preferred). Also with that custom bleed valve you mentioned, is that just tapped into the metal T shaped pipe on the front of the engine or somewhere?

 

If this one isn’t a daily driver, I would say bide your time and wait until you can. The other option is to get a tap and die set, and do the modifications yourself. The solution for the plenum hard line elbow is going to require some patience, and precise work without damaging the surrounding plenum material. Some ZR-1 owners plug both of those elbow ports after removing them. However, the only pictures I’ve seen is after they have it fully machined and re-powder coated so it just looks like a naturally smooth casting area.

 

Unfortunately it will have to be my daily for at least a few weeks until I can get my other car fixed. Is there anything else that needs to be done when blocking the lines? I saw someone say something in another thread about blocking one of the coolant reservoir hoses. Also I saw another person suggest keeping one of the coolant lines open to allow air to bleed of like it does stock(just slower) and since I'm only having issues with the drivers side I was wondering what your thoughts on that were, I don't really know how the coolant flows so I have no clue what would happen.