External head gasket leak at 2000 miles post rebuild.

[PhD_Polymath]

I rebuilt the 4.0 in my 2000 discovery with flanged liners about 2000 miles ago. I had a machine shop that specializes in Darton sleeve installs do the liner install, skim the liners flush with the block, check/skim the heads for flatness, and machine the crank and rods to spec.

I assembled the engine to the specs in the RAVE manual with the exception of using ARP studs for the heads. I know the use of studs is very controversial and expect to get schooled on how that could be the reason for my problems. For the record, I torqued to 100 ft/lbs as ARP designates.

After 2000 miles of trouble-free service, I noticed an exhaust leak "ticking" noise when the RPMs climb above 1500. I thought maybe this could be a manifold gasket, but when I looked closely at the engine for leaks, I noticed oily residue down the new looking block. The heads look brand new with no oil residue whatsoever, but the block has a film down the middle (under cylinders 3 and 5). I also noticed oil on the deck of the block where the serial numbers would have been present. After driving a few miles, I got a cylinder 5 misfire code.

I will pull the plug and see what it looks like and check the compression, but fear the worst.

If I have to redo the head gaskets, would I be dumb to use the studs again? I suspect this time around, I will retorque them after some interval (the instructions didn't mention that this needed to be done, but I recently read that this should be the drill for ARP studs). I am almost embarrassed with the outcome of my rebuild. However, I have a sizable investment into this truck with new cam, lifters, etc.

 

[seventyfive]

be careful removing the studs. If coolant entered the block threads the stud will be almost welded in place.

I learned something somewhat interesting while pulling heads, from a 4.6 with studs....

Use hand tools to pull the studs out, in other words use an allen socket. If you have a stud that will not come out, pull the bottom end, send it to the machine shop, have them remove it and helicoil every single head holt/stud thread.

OR

If the studs all come out no problem, get on the interwebs and find a helicoil kit (i forget the name of the place we get them from, but there is an interweb company that sells whole kits, the tools, helicoils, etc). Helicoil the threads, and do it properly.

regardless what you use, studs or bolts, helicoil the threads. Regardless what you use, studs or bolts, if you use a composite gasket you will be doing the gaskets again in 60-80k miles.

 

[jymmiejamz]

Use the factory bolts and you wont have any leaks until you get 60-80k miles on it. No one has problems with the torque to yield bolts, I don't understand why anyone would use studs.

 

[PhD_Polymath]

be careful removing the studs. If coolant entered the block threads the stud will be almost welded in place.

I learned something somewhat interesting while pulling heads, from a 4.6 with studs....

Use hand tools to pull the studs out, in other words use an allen socket. If you have a stud that will not come out, pull the bottom end, send it to the machine shop, have them remove it and helicoil every single head holt/stud thread.

OR

If the studs all come out no problem, get on the interwebs and find a helicoil kit (i forget the name of the place we get them from, but there is an interweb company that sells whole kits, the tools, helicoils, etc). Helicoil the threads, and do it properly.

regardless what you use, studs or bolts, helicoil the threads. Regardless what you use, studs or bolts, if you use a composite gasket you will be doing the gaskets again in 60-80k miles.

So, are you saying even if the threads are pristine and the studs come out easily, I should still helicoil every thread for the head bolts? The threads were very clean during the rebuild with not a speck of dirt or grease after the machine shop got done with the block. I was really hoping I wouldn't have to pull the block back out. I don't have garage space to redo it and the New England winter is right around the corner.

 

[jymmiejamz]

I wouldn't be surprised if the stud pulled the threads out of the block which is what is causing your leak. You won't know until you tear it down.