Front Edelbrock Performer Bolts Leaking Antifreeze

[posulli88]

Some back ground:

AMC30 Stock heads and Edelbrock Performer Intake installed with Felpro valley pan.

I had a coolant leak at my front bolts on the Edelbrock intake and at the front corner of the intake where it meets the block and heads. I removed the intake, cleaned everything up, used a new felpro valley pan to install. I used a combination of Permetex "The right stuff", Aviation gasket and thread sealent (thread sealant for bolts). This fixed my leak at the head/manifold/block intersection but the bolts still leaking.

To my knowledge this only happens after driving for a bit, parking the jeep and then ill come back the next day and there is a pool of coolant at those front bolts in the manifold.

I drained coolant. Let dry out for a day, chased threads, installed bolts this time with Permatex #2, let dry for a day and and refilled, burped coolant system. This held up for a couple weeks and is now leaking again.

What can I do to stop this? I did a lot of research on how to install the intke manifold and what gaskets and gasket makers to use. Was very careful and precise. Just trying to stop this never ending leak.

Thanks!

[letank]

The fact that it is happening after you drive a bit sounds like thermal expansion with leak and reseal when the 2 dissimilar metals set tight.


Do a cooling pressure test to confirm the origin of the leak.


The time I had some leak with pool in the front valley of the intake manifold was a leaky thermostat housing... the paper gasket... when I removed the housing bolts, one of them broke... but the extraction with wise grip was painless. I used RTV silicone labelled for thermostat housing... no paper gasket... that was a few years ago, no leaks.


Regarding the thermostat housing, some have a big gap, lay it on a flat surface to make sure that the flange is level.

[babywag]

Do a pressure test when warmed up.
Most likely a leak from tstat housing.
I have seen several housings that were cracked.

Was the intake used or new, also seen many used intakes with poor coolant ports(corroded), or someone took a 3m scotch bright disc to intake and made it wavy. While they clean up surfaces well, the surface gets all f'd up and don't seal.

[posulli88]

Thanks for the insight. Ill do a pressure test. Do I need to make sure the thermostat is open for the pressure test to find all leaks? I thought it could be the thermostat housing but hadn't seen any coolant at the intersection. I purchase the performer manifold new.

[letank]

Thanks for the insight. Ill do a pressure test. Do I need to make sure the thermostat is open for the pressure test to find all leaks? I thought it could be the thermostat housing but hadn't seen any coolant at the intersection. I purchase the performer manifold new.

No need for the thermostat to be opened, start pressure test at 6 to 8 psi... then increase if needed, but by 8 psi most of the leaks appear , remember that the max is 15-16psi

[posulli88]

Ok, waiting for parts store to get their rental pressure tester back so I can use it.

In the meantime I did do a closer examination and found there is coolant leaking at the thermostat housing. I will pull that off, sand down flat and use permatex coolant sealant. Do you all typically use a paper gasket (felpro), or just sealant?

The worse news: It appears the back of the intake manifold is leaking coolant at the head / block / manifold intersection so looks like I need to remove manifold and reinstall. What is the best way to install the intake manifold with the valley pan? Combination of aviation gasket and RTV? This will be the second time have have to reinstall the manifold and want to get it right this time.

[Cliff]

I know this may contradict conventional wisdom, but I never use the valley pan. I also have never used thread sealant on the bolts, use permatex #2 only on a high quality gasket, and use RTV on the ends, discarding the seals entirely. I have never had a leak.

I do one more thing - I drill 1/16" holes along the ends of the manifold where it seals to the lifter valley surface, and alternating holes on the block, only 4-5 on each surface. This anchors the RTV on the ends. These holes are only 1/8" in depth, just enough to get some RTV in the hole.

[posulli88]

Did the pressure test today. Confirmed its leaking at the thermostat housing and front and rear intake manifold/ head/ block intersection. So I will have to redo the manifold. I going to use Permatex ultra grey this time so I have a longer working time to get everything installed. 3rd time is a charm I hope.