Head studs leaking coolant
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Teching In
Joined: Nov 2012
Posts: 19
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From: Dexter, Oregon
Head studs leaking coolant We've been wrenching on a 95 lt1 for a while now; it's been bored 30, forged rotating assembly, le2 h/c/i, mls cometic head gaskets and arp studs with 12 point nuts. The studs were sealed to the block with permatex aviation and almost all of them, inside and out, are leaking coolent between the nut and the threads.
I'm sick to my gut just thinking about this whole situation, so any kind of insight is greatly appreciated.
Thanks in advance
I'm sick to my gut just thinking about this whole situation, so any kind of insight is greatly appreciated.
Thanks in advance
IMO Permatex #2 is better than the Aviation Form A Gasket, it seems to stay more pliable. Perhaps you could try draining the coolant then loosening the head stud nuts to 30 ftlbs or so, then remove one stud at a time to clean the threads and reinstall with the sealant of your choice. Re-torque the stud nuts to spec as on a new installation . I would think this procedure would not harm the head gaskets.
Last edited by guppymech; Nov 21, 2013 at 01:07 AM.
You have a couple options. Remove each stud individually, clean and reseal using a good RTV like permaseal ultra black. Or you can purchase those GM veggie tabs to drop in the coolant system which may or may not work.
Staging Lane
Joined: Sep 2012
Posts: 85
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From: Virginia Beach, VA
I would stay away from the GM coolant tabs. In my experience, they seem to work by accumulating small particles insoluble material thereby clogging a leak source. With most of your studs leaking coolant, you'd spend a ton of money on the tablets, clog your radiator, and still have intermittent leaks. I have used RTV for years to seal both head bolts and studs w/o leaks.
Good luck fixing the problem.
Good luck fixing the problem.
I had the same problem after I finished my 355 engine. After doing some research it seems leaking head studs past the nut is a common problem. I had 2 studs on the very bottom row on each bank leak a few drops a minute, pulled the valve covers and none of the studs inside the engine were leaking. I couldn't remember if the studs under the valve cover went into a blind hole or not so I doubled checked to be safe. Being all my coolant leakage was on the outside of the engine I took a gamble and used some of the GM coolant seal tabs. I only put in 1/3 of the recommended amount that the package had listed. After about 4-5 heat cycles all leaking stopped. Have about 4500 miles on it and not a drop so far. Some say the seal tabs are not good to use but after talking to my engine builder and a had full of local guys that had used them with no problems I figured they are worth a try.
Loctite makes a very good Teflon thread sealant. It is available at most plumbing stores. It is not cheap, but I have had great luck with it. I have pulled and replaced a lot of heads at the track with no leaks.
I would stay away from the GM coolant tabs. In my experience, they seem to work by accumulating small particles insoluble material thereby clogging a leak source. With most of your studs leaking coolant, you'd spend a ton of money on the tablets, clog your radiator, and still have intermittent leaks. I have used RTV for years to seal both head bolts and studs w/o leaks.
Good luck fixing the problem.
Good luck fixing the problem.
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I have always used ultra black rtv. Never a problem. I also learned studs don't run any faster than bolts. Everybody has the therories about this, but I proved to myself both give the same ring seal, make the same power, and go down the track with the same time slips. But, you need to use which ever was used with the torque plate when your block was honed. Just assuming your block was torque plate honed. They don't distort the cylinders the same when torqued. Don't change back and forth. The shop that I use always puts the torque plate on with my head bolts, torqued with my torque wrench.
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ARP sells liquid teflon thread sealant but I believe its just repackaged loctite liquid teflon sealant.
I use the liquid teflon sealant on those older blocks were the bolts go into a coolant passages.
In the past we have used the coolant tabs and run a few heat cycles to seal it up. Then flushed the cooling system so the radiator doesn't get clogged up.
I use the liquid teflon sealant on those older blocks were the bolts go into a coolant passages.
In the past we have used the coolant tabs and run a few heat cycles to seal it up. Then flushed the cooling system so the radiator doesn't get clogged up.
Do NOT use ARP Thread Sealant! I ran permatex thread sealant for years no issues, this past year used arp's and 4 bolts per head leaked. Junk! Anyways do you have a part number for the arp head studs 12 point? Thanks
Agreed with that^
Do NOT use any kind of Teflon or moly anything to seal threads exposed to coolant. Moly and Teflon are LUBRICANTS, not sealants and they will wash away.
THIS is the stuff to use. Coat the stud threads heavy. It won't wash off. Coolant, heat and fuel resistant. In 50,000 miles pull the studs and it'll still be in the threads.
Do NOT use any kind of Teflon or moly anything to seal threads exposed to coolant. Moly and Teflon are LUBRICANTS, not sealants and they will wash away.
THIS is the stuff to use. Coat the stud threads heavy. It won't wash off. Coolant, heat and fuel resistant. In 50,000 miles pull the studs and it'll still be in the threads.
Last edited by Paul Bell; Dec 2, 2013 at 07:51 AM.
