Rear Head Bolt Seepage Continuous Problem - What To Do

94mustangsvt · Jul 29, 2014

The driver side rear lower head bolt on my car keeps leaking coolant. I always put ARP thread sealant on all the bolts, but recently when I changed the cam I tried pulling the one bolt out and resealing it again.

After a few days, the leak is now much worse. The car runs great and has no coolant in the oil. The current block has maybe 10K on it because I got a refreshed level 10 bare block from DSS. However, the seepage issue was a problem on my old block as well so a block issue is pretty much ruled out.

Are the AFR heads maybe warped somehow? Last time I had them checked out they certainly didn't mention anything. Anyways, I'm trying to figure out what to do at this point. Should I try throwing a new head gasket on that side and hope it works or maybe try torquing the whole head down five more pounds? Any suggestions would be great, thanks.

toyman · Jul 29, 2014

Aren't these Torque-To-Yield head bolts? See here.

94mustangsvt · Jul 30, 2014

toyman said:
Aren't these Torque-To-Yield head bolts? See here.

Stock are, but I have ARP head bolts. Supposed to be 80 ft. lbs on the long bolts and 70 ft. lbs on the short bolts with the AFR heads. I currently have them all at 75.

BLWNBYU · Aug 3, 2014

Which thread sealant did you use?

RichV · Aug 3, 2014

I had a funky leak in a tranny one time that I was chasing for over a year. Turned out it was a hairline crack in the aluminum case. They had to put it under a blacklight to see it.

I know this will be a PITA, but if you swap side on the heads and see if the leak follows the head or stays. At least you'll know to suspect the block or heads.

94mustangsvt · Aug 3, 2014

BLWNBYU said:
Which thread sealant did you use?

ARP thread sealant

94mustangsvt · Aug 3, 2014

RichV said:
I had a funky leak in a tranny one time that I was chasing for over a year. Turned out it was a hairline crack in the aluminum case. They had to put it under a blacklight to see it.

I know this will be a PITA, but if you swap side on the heads and see if the leak follows the head or stays. At least you'll know to suspect the block or heads.

I had the same issue on a previous block though so I'm suspecting the heads. I'm going to try taking it down 5 more ft. lbs. in hopes of a non-big pain in the ass fix.