Coolant outlet bolt torque and how far over can it go? - ZR-1 Net Registry Forums

1991 Corvette ZR-1 · 11-11-2022

I am having occasional trouble with the coolant tubes weeping on the bottom near the mating surface with the injector housing. I had my top end ported by Pete and also had him get the old seized torx bolts out while he was at it. I replaced those with stainless from Jerry?s, also gaskets as well. Gaskets were installed dry and I did not see anything specifying they be smeared with sealant.

I made sure all surfaces were clean and smooth. Converted the 89 inch pound suggest torque to ft lb and it came out to about 7.5. That seemed way too low when every other bolt on this engine seems to have a higher torque spec. Is this a misprint? I was good for a month, then I noticed traces of coolant on the cam covers.

I figured they are loose so I broke out the torque wrench and no they are still torqued to 7.5 lb ft. I bumped it to 9 lb ft and torqued them again. Fast forward about a year and another torque to 10 lb ft and they are weeping again. So now I am in a bind. I hate the idea of draining all the coolant to redo both outlet tubes. Is there a safe amount over in which I can torque these bolts? I figured the heat cycles are slowly shrinking the gaskets, allowing them to weep coolant.

Lesson learned, from now on any gasket that goes on this vehicle will have a smear of appropriate sealant on both sides before being reassembled.

AndrewL · 11-12-2022

I can't tell you what if any additional capacity there is to torque those bolts, but to my mind... dumping the coolant and applying a thin layer of rtv is less of a pain than having to fix damaged threads in your aluminium injector housings.

Dynomite · 11-13-2022

Quote:

Originally Posted by AndrewL

I can't tell you what if any additional capacity there is to torque those bolts, but to my mind... dumping the coolant and applying a thin layer of rtv is less of a pain than having to fix damaged threads in your aluminium injector housings.

Concur..... Never go over the recommended Torque especially on Aluminum.....I always stay a bit under the Torque Value especially on parts that may be removed several times later such as the Plenum. 89 In-Lbs Torque or a bit less is the correct Torque (on the coolant outlet pipes to Injector Housing T-30 Torx) and it helps if you use a 1/4 " Drive Torque Wrench on the smaller bolts. A 3/8" Drive Torque Wrench is "Just Too Big for the Task" on the smaller bolts especially into Aluminum.

Post 4 - General Bolt Length, Bolt Torque, Loctite, and Tools

Permatex on gaskets associated with Oil and Coolant.
There are several opinions on this but I use a very light coat of Permatex 300 Form A Gasket on both surfaces of mating parts of all assemblies in contact with oil or water (water pump, oil pan and oil filter housing assemblies). I always use a thin coat of Permatex on the Oil Pan Drain Plug, Transmission Fill and Drain Plugs and Differential Drain Plug also. This not only helps seal the plugs but also acts as a thread locker (A little less bolt torque with a good sealant). Tighten just tight enough to not leak on all drain plugs.

Post 5 - Use of thread Lubricants, Loctite and Sealants

1991 Corvette ZR-1 · 11-14-2022

I appreciate the feedback. I had actually considered that my torque wrench is not accurately metering at that low of a level of torque spec. I did try 12 lb ft prior to making this thread. So far, the leaks have once again stopped. If the leaks come back, I will drain the coolant and use sealant smeared on both sides of a new pair of gaskets.

CamP · 11-14-2022

Permetex Moto Seal , aka Yamabond 4 to old motorcycle guys, is excellent on oil and water related gaskets. It's also very easy to remove when you have to reservice the part again.

I've even used it on a old plenum gasket where a 1/2" portion of the gasket was missing on an intake runner. It sealed it well. It came off with the old gasket when I had a new replacement in hand, so no scrapping was required before installing the new gasket.

Good stuff!

Z51JEFF · 11-14-2022

I would get both mating areas dry and go over both surfaces with a flat block and sandpaper to make sure both surfaces are true and use some sealant.

11-11-2022	#1
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 297	Coolant outlet bolt torque and how far over can it go? I am having occasional trouble with the coolant tubes weeping on the bottom near the mating surface with the injector housing. I had my top end ported by Pete and also had him get the old seized torx bolts out while he was at it. I replaced those with stainless from Jerry?s, also gaskets as well. Gaskets were installed dry and I did not see anything specifying they be smeared with sealant. I made sure all surfaces were clean and smooth. Converted the 89 inch pound suggest torque to ft lb and it came out to about 7.5. That seemed way too low when every other bolt on this engine seems to have a higher torque spec. Is this a misprint? I was good for a month, then I noticed traces of coolant on the cam covers. I figured they are loose so I broke out the torque wrench and no they are still torqued to 7.5 lb ft. I bumped it to 9 lb ft and torqued them again. Fast forward about a year and another torque to 10 lb ft and they are weeping again. So now I am in a bind. I hate the idea of draining all the coolant to redo both outlet tubes. Is there a safe amount over in which I can torque these bolts? I figured the heat cycles are slowly shrinking the gaskets, allowing them to weep coolant. Lesson learned, from now on any gasket that goes on this vehicle will have a smear of appropriate sealant on both sides before being reassembled.

11-12-2022	#2
AndrewL Join Date: Dec 2020 Location: Sydney, Australia Posts: 74	Re: Coolant outlet bolt torque and how far over can it go? I can't tell you what if any additional capacity there is to torque those bolts, but to my mind... dumping the coolant and applying a thin layer of rtv is less of a pain than having to fix damaged threads in your aluminium injector housings.

11-14-2022	#4
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 297	Re: Coolant outlet bolt torque and how far over can it go? I appreciate the feedback. I had actually considered that my torque wrench is not accurately metering at that low of a level of torque spec. I did try 12 lb ft prior to making this thread. So far, the leaks have once again stopped. If the leaks come back, I will drain the coolant and use sealant smeared on both sides of a new pair of gaskets.

11-14-2022	#5
CamP Join Date: Jun 2012 Location: fort worth Posts: 183	Re: Coolant outlet bolt torque and how far over can it go? Permetex Moto Seal , aka Yamabond 4 to old motorcycle guys, is excellent on oil and water related gaskets. It's also very easy to remove when you have to reservice the part again. I've even used it on a old plenum gasket where a 1/2" portion of the gasket was missing on an intake runner. It sealed it well. It came off with the old gasket when I had a new replacement in hand, so no scrapping was required before installing the new gasket. Good stuff! Last edited by CamP; 11-14-2022 at 02:44 PM.

11-14-2022	#6
Z51JEFF Join Date: Dec 2007 Location: Fremont,Ca Posts: 3,049	Re: Coolant outlet bolt torque and how far over can it go? I would get both mating areas dry and go over both surfaces with a flat block and sandpaper to make sure both surfaces are true and use some sealant.