Have a head gasket(im 99.9% certain its the head gasket) thats weeping in the passenger side rear corner. Engine has not been run.

Machine work was done by a very reputable shop so I dont suspect anything there. Head and block were used, but inspected, although I dont know to what degree beyond visual for cracks.

Cometic MLS .040 gasket.

ARP 234-4317 studs torqued to 25-50-80 and small bolts torqued to 28 or whatever that spec is.

Steam ports are dry before anybody says anything about that. Plug for ECT port was pulled and resealed and is dry. Its definitely coming from the head gasket back between say the #7 and #6 bolt locations.

I have a replacement head gasket ready to go...

Anything to try before tearing into it to replace it? Should I crack all the studs loose individually and re-torque? Just bite the bullet and change it?

My buddy suggesting I put the vacuum coolant bleeder on it and see if it holds a vacuum(doubt it will).

 

I don’t think you’ll find anything wrong with the new headgasket on a freshly rebuilt, unstarted engine. Especially a Cometic. You’ve likely got a burr, or a deep scratch…or maybe even a crack, if you’re certain you’ve verified it’s not the steam vent or the cts hole plug.

 

im 99% certain its not a steam port or the ECT plug.

Im hoping for no cracks cause that would be catastrophic...

I dont remember seeing any burrs or anything like that, but its gotta come apart.

 

Best to re torque the heads after the first heat up cool down cycle if using non torque to yield fasteners. I assume you have gotten the engine up to operating temperature. If not do so and let cool down preferably over night. Loosen one fastener in proper sequence and bring back to torque. Loosen the next in sequence and bring back to torque. Continue until all are re torqued then do the same on the opposite bank. If the problem persists there is no option other than pulling the head and inspecting things further for flatness and surface finish. Cometics require a smooth surface finish under 50 RA. Any rougher than that they tend to **** coolant out the sides.

 

the car doesnt run. Needs to go to the tuner... so no it hasnt been run, as my OP says. I dont want to take the car to my tuner with a weeping head gasket and possibly have coolant blow out all over the dyno... I cant get the car hot without taking it to my tuner... so im in a cycle here...LOL. I already thought about trying to heat cycle it and see if it would seal, but I just dont think thats possible.

The shop that did the machine work is very well known LS shop in the country. Surface finish, while I dont know EXACTLY what the RA was, was damn good. They knew I was using Cometic MLS gaskets. I dont want to name that shop simply because I dont believe any of this is on them as far as their machine work.

 

Took the whole top and passenger side head off. Everything looked fine. Literally zero smoking guns. Sent pics to a few guys who said they didnt see anything either. My fab guy said "honestly looks like it never hit torque", which I have no clue as I torqued both heads with the same torque wrench at the same time(well I mean 30 minutes apart) so there "shouldnt" have been any difference. Talked to the shop that built bottom end and freshened heads and they agreed that it was possibly a fluke. He said clean head gasket well including blowing out between layers and check all holes for burrs that would keep the gasket from seating fully. I also noticed during my research that the GM gaskets have some type of rubber around most holes, my guess is to aid in sealing. The Cometic gasket I have does not have that and I assume relies on crush only to seal(or not seal)...

Put a new gasket on(Cometic .040) and sprayed it with copper, retorqued studs to 25-50-80. Got the rest of the motor re-assembled and refilled with oil. Spun the motor over a bit without the ECU on then decided to run the Haltech wizard again because I have installed fuel pressure sensor plus both O2 sensors... End of wizard is basically "attempt to start engine" or some such... well ****... she fired up. 2 months ago it wouldnt fire up(no O2's, but Haltech guys said not needed for idle). Im wondering if my fab guy wasnt on to something that it wasnt torqued properly(again I have no clue how or why not) and wouldnt make compression and thus wouldnt fire.

I ran out of time to put coolant in it, so ill do that Sunday before I take it to the tuner on Monday. Hopefully a new gasket with copper spray and re-torque will have solved it.

 

I would put wrench on 70-75 pounds and just run across them to make sure TQ is still there. Not enough TQ to move them if OK but enough to move them if not OK. I have found sitting overnight even with the ARP lube and studs I have 1-2 that need that extra tweak.

 

Its a moot point at this point since I changed the gasket yesterday... BUT, I put an 80ft. lb. torque wrench(same one I used to originally torque the heads) on it 2 months ago when I first noticed the weep and nothing moved.

 

Well not what I wanted to report.

Vacuum bled it today and within 5 minutes the head was leaking from the same place. Right at the #6 head bolt. Talked to 2 guys and both suspect a crack in the bore of the bolt hole. These heads came from facebook marketplace so unknown origin or treatment...

Both guys suggesting to order up a new GM LS3 head, get it decked to cc the chamber properly to match the other head and move on with life. They said to pay to have it inspected just to be told "yea its junk" is wasted money.

Going to call the shop that machined them tomorrow to get their opinion on how to move forward...not blaming them at all as both of the guys I talked to said "yea I would glance at the bolt holes, but thats not really my concern when inspecting a head".

Im open to any other ideas to check out before I order a head, but at this point, 2 head gaskets leaking from the same place leads me away from "2 bad head gaskets"...

 

Drop some tracer dye product in the coolant and pressure test it to promote leak before you tear it back down again. You need to know for sure where the leak is originating imo.

 

It was very obvious where the leak was coming from... directly under the #6 bolt in between cyl 6 and 8... Everything else was dry, there was no time for the water to spread. I believe the first weep the water had been weeping for a while and I couldnt get a good idea of exactly where it was coming from... this time...obvious.

So its either the block is cracked and coolant is pushing up or the head is cracked and coolant is flowing down...

But its coming from that bolt location and was weeping out the top of the head gasket... I obviously cant see the bottom of the head gasket right there, but I can see the top and its coming out right there... right where the rivet in the gasket is which is adjacent to the #6 bolt.

 

You could try a GM sealant tablet. Drop it in the radiator, and heat cycle it a couple times. I use them with all my sleeved block builds, per Steve at RED’s recommendation. GM drops the same tablet in EVERY vehicle they build on the assembly line. It’s a matter of insurance for hose sealing, and whatever else that might weep. It’s worth a try. Summit Racing sells the tablets. Just use one. More than one and you’re just turning the coolant circuit black and gumming up your radiator.

 

A buddy suggested trying that.

if I have an actual crack in the head or block these tablets wont really do anything to fix that though will they?

I wish I had a better answer than "maybe"...

I really dont want to pull it all back apart again to keep looking for smoking guns.

 

The factory's ginger tablet (that's what it actually is... ginger) can't tell if a leak is a crack or whatever else. It just fills in the gaps and gums everything all up. I personally abhor them, butt sometimes ya gotta do whatcha gotta do with whatcha got to do it with.

 

At this point I have to sideline the project for like 3-4 weeks. Traveling a bunch, have a track weekend I have to get my Vette ready for now, getting shop spray foam'd and air conditioned, etc...

I talked to the shop that did the machine work and built the bottom end this morning to get their ideas. The guy said a head cracking there is fairly rare, but not out of the realm. His suggestion was pull it all apart, pull the studs out of the the hole I think is leaking plus the ones on each side, blow them out with air really well and see if they fill up with water just sitting there... might have to add a bit of water to the block depending on where I end up after yanking the head. That will tell us if its a block or head issue. He agreed if its a crack in the head, the head is junk, no real way to repair a crack down in a bolt hole. If its the block he also didnt like the idea of machining out the bolt hole and putting a thread insert in it. He said no way to really stop the crack and it will likely propagate... If the bottom of the bolt hole is blown out, might be salvageable just by running a sealant on the stud. I have access to another 6.0 aluminum block since a buddy of mine and I bought ours at the same time and he's likely another year+ plus from getting his going so we can find him another block...

So I think I have a path forward to at least figure out if its block or head, but I am going to wait until my shop is air conditioned to get back on this car.

 

You might want to pull that one stud and look down into the hole. I am wondering if you have a hairline cracked block where the head bolts goes in or at the bottom of it. The resolution would be to put some permatex / thread sealant at the top of the threads. Normally the holes are blind tapped but you might have a tiny crack causing the water to go up the bolt and out the nut there.

 

I ordered a cheap borescope from Amazon. I wont have time for a week or so to pull the stud and check it out though.

 

No sir.

 

yea, might buy some time to run the motor a bit, but I feel like its just a finger in the dyke so to speak.

Same thing with trying to use a thread sealant on the stud.

 

They use thread sealant all the time on engines. The old BBC and small block Chevys did not have blind tapped holes. Several head bolts went right threw to the water jacket same thing with water pump bolts.