Leaking coolant from head gasket

[Darius]

Just fired my motor up last week after troubleshooting electrical problems and now after starting it up and letting it idle for a minute, coolant dripped on the floor. I thought maybe I didn't get a heater core hose on tight enough or something small, but upon further inspection, it is leaking from the head gasket on the exhaust side of the motor by cylinders 4-6. Mostly leaking between cylinders 5 & 6 but it is so slow that it is almost like a sweat. I checked the motor for compression before startup and it was fine (~150 psi for all cylinders).

I took the head off and installed a new Cometic head gasket and fastened with new ARP head studs. Torqued the head down to ARP specs for their studs and that was it. The don't understand how it can leak. How does one go about correcting this? I've been fighting this motor from day one so this does not really come as a shock.

[blues14]

hope its not the problem...but maybe a warped head?

[98birdls1]

Did you have the head surfaced? And the block decked? On a motor as old as the RB25's there could be some warping or pitting that is causing the leakage.

How did you remove the old headgasket?

Hopefully it was just improper installation. Hate to see you have to pull the motor to check the block and head for imperfections.

Luke

[Bluefire]

The head and block should always be checked for warping when they are separated. Also a compression test is a very basic test. You really need to do a leak down to determine if the motor is in good shape.

-Bluefire

[Joe]

only problem is a leakdown may not reveal the problem

its leaking outside the combustion chamber, the leakdown wont test for that

the head on a rb should ALWAYS be checked when you install a MHG because its aluminum its a little (see: a lot) harder to warp the block because its steel.

[Darius]

When I pulled the head, I peeled off as much of the OEM gasket as I could but some of it came apart. So I painstakingly peeled the rest of it off while using a razor blade to separate it from the block. Not a whole lot stuck to the head as I remember, it was mostly on the block.

At this point, I need some suggestions because I seriously hesitate to run it at all in this condition. If I AM taking the motor out and pulling the head, I might as well build the whole gat-damn thing. Rods, pistons, rings, balancing, etc. While I'm at it I might as well paint the engine bay as well. But then again I just want to see the thing roll down the road after having it in my garage for nearly 8.5 months. Somebody give me a recommendation here because thinking about pulling that motor and re-doing everything makes me sick.

[300Plus]

Not perfect answer but maybe just yank the head back off, have it resurfaced and try it again with a new head gasket.

[USMCgetsome]

Not that hard to take the head back off. Just make sure you take off the turbo and then unbolt the head. I did it. It was fairly easy. i replaced the hg with a newer stock. Same as u. I used a phenolic scraper to get off the all the material. Honestly man. Do what is suggested. I know it sucks but think of it this way if you redo it a 2nd time you'll know what the real problem is and know if you need to re-deck or whatever. Get a buddy and some beer and go to work!

[eh?]

Did use copper spray on the HG? Did you TQ in 3 or 4 steps? How much did you TQ it too?

Be very careful. I ruined my built RB25 (cry) because the flippin tomei HG wouldn't seal properly. I had to TQ up to 80ft/lbs before it stopped leaking. By then it was too late.

[Darius]

When I installed the head gasket, I did not use a copper spray and I tightened in three stages according to ARP's specs with the moly lubricant they supplied. I don't remember the exact torque specs, but I followed them instead of the Nissan FSM specs. I can't imagine that pulling the head with the motor still in the car is going to be "easy" with the factory intake manifold. The coolant lines and bolts are a PITA to get at from the bottom.

Assuming I pull the head, how does one go about checking the "flatness" of the head and block?

[98birdls1]

For the head take it to a machine shop and have them check and/or resurface it. If you used the OEM HG it may be neccesary to get another HG.

For the block: I'm not sure if a machine shop can check the block inside the car. Call and ask on that one and have it towed there.

Live and learn. Always, resurface at least the head (best to block as well) when changing a MHG. Good luck.

Luke

[Yellow4g63]

When I installed the head gasket, I did not use a copper spray and I tightened in three stages according to ARP's specs with the moly lubricant they supplied. I don't remember the exact torque specs, but I followed them instead of the Nissan FSM specs. I can't imagine that pulling the head with the motor still in the car is going to be "easy" with the factory intake manifold. The coolant lines and bolts are a PITA to get at from the bottom.

Assuming I pull the head, how does one go about checking the "flatness" of the head and block?

You brought it to 70bls of TQ right?

[Darius]

I just double-checked the ARP instructions and that says 70 ft lbs, so that's what I tightened them to.

[Joe]

I just double-checked the ARP instructions and that says 70 ft lbs, so that's what I tightened them to.

you did them in steps right?

like 30ftlbs, 50ftlbs, then 70ftlbs?

[Darius]

That is probably about right since I did it in 3 steps and started at 29 Nm like the FSM says, then stepped it up to 70 ft-lbs. Each time I loosened the studs, then retightened to the higher torque. Is that how you're supposed to do it or should I try retorquing the head without cracking them loose each time?

[Bluefire]

It shouldn't be that big of a deal, but personally after the first torque setting I always loosen them and then torque to final spec.

-Bluefire

[Darius]

eh? - Do you recommend a copper spray-on coating on the head gasket? and if so, what are the benefits?

[eh?]

I used permatex http://permatex.carshopinc.com...80697The copper fills in imperfection in the mating surfaces. The problem with metal HG's is that they will not fill in as well as a soft organic gasket. IT's common to have a metal HG leak because of that. Also the copper will withstand the high temps.

[Darius]

That's what I thought. And along those lines I thought the two Viton gaskets sandwiching the metal one would provide that. Copper being that much more malleable might deform into crevices better. I don't know, but either way I think the head is going to come off, be resurfaced, then reinstalled with the headgasket coated in that Permatex copper spray-on coating just for good measure.

I'll check the block at the same time of course.

[Darius]

After a month of pulling the head while the motor was still in the car and resurfacing/reinstalling it, then forgetting to put the three auxiliary head bolts on and having to uninstall/reinstall in intake manifold AGAIN, I got the motor running last night. DOH! Note: Don't get plowed while working on the car...

Weird thing was that the starter isn't turning over as readily as I would like. I turn the key and half of the time it just clicked. But if I turned the key fast a few times and held it in the third time, it would fire right up. Seemed like the system just needed some time to get the power to work it's way in there from the battery. I'll get things completely installed and then it will hopefully hold coolant this time.

Just in time for winter!

[gawdzilla]

make sure your grounds are good and are making good contact. make sure your battery terminals are tight. the starter draws a lot of amps, and it will do the clicking if there isnt a solid connection

[Darius]

Before I quit last night I made sure to clean the battery ground connector really well, so hopefull that will help.

[Darius]

Everything mechanically works now but I ****ING love to update this thread with bad news, so here goes. I was working on the car to bleed my lifters (see another thread) when I noticed a little spot of coolant AGAIN. It came from the same location so I called Cometic to get their viewpoint and the guy (Kevin) told me to heat it up to operating temp for a while and then retorque the head. I don't know how much of a difference that is going to make, but I will give it a shot. He said to send pics of the gasket and again...I don't know what he'll be able to tell from that. He basically told me to make sure the rivets that hold the gasket together clear the mating surface. If it doesn't seal after that, Nengun is going to get a $3000 order from me (including a new head gasket) and I'll call it quits on this summer.

[Bluefire]

Try and get your hands on a water pressure tester. It comes with adapters that fit to your radiator, and then a hand pump with gauge. You can then pressurize your entire cooling system and search for leaks.

-Bluefire

[Darius]

I wish I would have had that tool 6 months ago before I tried reassembling and disassembling the motor half a dozen times. I'm assuming the kit comes with instructions as far as the typical pressures of a coolant system and signs/symptomes of a leak? External leaks should be obvious, but pinpointing internal ones must be impossible. I'll look into it.

Thanks

[Kansei240sx]

This may sound silly, but do you have the head lined up correctly? There are 2 or 3 10 mm screws on opposite ends of the head that you use to line up the head and then put the head bolts in.

[Darius]

I replaced the head bolts with ARP studs, so there's no real room for misalignment.

[Kansei240sx]

You'd be suprised. Thats what we thought when we did my friends RB20, but when we got to putting those three little bolts in they didnt go in becuase of that 1-2 mm's of play.

[Darius]

Never thought I would revisit this **** ING thread, but after 725 miles of driving after the rebuild, coolant is finding its way into my oil again. I noticed that my catch can had separated into yellow milk and water.

I'm going to have to take the cams out and everything else in an attempt to retorque the head nuts. If that doesn't work, I am going after Cometic.

[gawdzilla]

This may sound silly, but do you have the head lined up correctly? There are 2 or 3 10 mm screws on opposite ends of the head that you use to line up the head and then put the head bolts in.

I think you're referring to the 2 or 3 dowels between the mating surfaces? This may be a stupid question, but do you have those in? Either way, sucks to hear man.. that thing just got back on the road