head gasket leak??? with arp studs

[pyro7890]

i have a 1.6 na 11mm it had a bad head so i bought a rebuilt one and put arp head studs in and made sure there was enough lube on them and tourqed them and i have a coolant leak any ideas as to the problem

[maxfax]

Where abouts is the coolant leak located? 

[pyro7890]

back right side of the motor

[pyro7890]

i think i know what i want to try already but i just wanted to see if other agreed. i am going to take the head off, make sure the head and the block are not warped, chase the threads put a new head gasket on  and try again

[Mark(The Miser)UK]

i think i know what i want to try already but i just wanted to see if other agreed. i am going to take the head off, make sure the head and the block are not warped, chase the threads put a new head gasket on  and try again

Slight distortion should pull out with the studs.
I'd be inclined to check with the head off, for some scoring/divot, corrosion around the water passages.
Maybe it was your block all along, and not you previous head, or maybe the studs cracked the block this time.

[Quantum TD]

Another possibility is that the block was cracked to begin with (or, at least weak on the rear head bolt). The two places where those 11mm blocks tend to crack is on the right and left rear head-bolt holes.

I hate to be the bearer of bad news, but I'm speculating that a notable leak from a properly torqued head gasket may be due to a crack leading from the head bolt to the water jacket.

I'm hoping I'm wrong.

[2strokesmoke]

I too had a slight coolant leak,after replacing the head gasket on my 1.6NA  11mm
My block has no cracks and both head and block have less then .003" distortion.Gasket surfaces,cleaned immaculate.
I also used ARP studs and torqued to 80 ft lbs and retorqued agian hot.
After searching the forum and asking advice,it was recommended to increase the torque
I backed off each stud 1/4 turn and retorqued to 85 ft lbs(one at a time) in sequence.(I was sweating it,but it took the 85 ft lbs)
coolant leak is gone.
Might be worth a try??
special thanks to those who gave advise .

[zukgod1]

Been there doing that

I've not had a problem with a 1.6 but currently on 1.9 I'm having the same problem.

I misread the torque specs and tightened them not enough, went back and added 90 deg to all but too late. I have a new gasket sitting here if I ever get the time..

[Quantum TD]

I remember having this debate with 53Willys a few years back. He was having HG problems with ARP studs. He was afraid to overtorque the head. He had followed the ARP specs to the T. As it turns out, he overboosted and blew the fiber headgasket. But in the process of trying to save it, I pointed out that the OEM stretch bolts finish up somewhere in the 110-120 Ft-lbs range when all is said and done. I thought it would be safe to push the ARPs up to 100 ft-lbs without consequence. I think in the end, he went up to 105-110 ft-lbs and the bolts and block were fine. I'm not sure if the 11mm fact might make a difference in that though.

As noted by others, if you catch some seepage early, you can often retorque and save yourself from redoing the HG.

Probably worth torquing those bolt up to 90: see what happens. Then 95, see what happens. And if it still leaks, try 100 and see what happens. Beyond that, you may still keep going. Worst case scenario, your block is already cracked and you won't risk anything. Best case scenario, you solve your problem simply by adding a bit more (acceptable) torque to the nuts.

Good luck.

[Mark(The Miser)UK]

I think I'm correct in thinking that a solid bar increases in strength by the 4th power of it's radius. So a 10 % increase in diameter gives 40 to 50 % increase in strength, or a reduction from M12 to M11 is 'ball park'  1/3 weaker for the same material...

[RadoTD]

I think I'm correct in thinking that a solid bar increases in strength by the 4th power of it's radius. So a 10 % increase in diameter gives 40 to 50 % increase in strength, or a reduction from M12 to M11 is 'ball park'  1/3 weaker for the same material...

I think you may be mistaking this with something else. Tensile strength is what matters here, ART studs being in the 180-220,000psi range. ARP's studs are undercut.. I don't know why they do that, but lets say the 12mm is undercut to 10mm and the 11mm undercut to 9.17mm. Using 180,000psi, the tensile strength of the 12mm stud where it's undercut is 6980lbs, the 11mm studs is 5860lbs, an increase of 19% over 11mm studs.

If you want to figure out the actual force the stud is torqued to, it would have to do with the tangent of the slope of the thread. Add that to the peak cylinder pressures and divide by the studs around that cylinder and you get the max force applied to the studs. Multiply that difference by the elasticity, given their preload and you find out how much they stretch. If that's greater than the amount the head gasket can expand, you leak coolant. Fiber would typically just blow at that point as it's not held together by being squished between the head and block.
But I don't feel like figuring all that out right now 

[Mark(The Miser)UK]

I think I'm correct in thinking that a solid bar increases in strength by the 4th power of it's radius. So a 10 % increase in diameter gives 40 to 50 % increase in strength, or a reduction from M12 to M11 is 'ball park'  1/3 weaker for the same material...

I think you may be mistaking this with something else. Tensile strength is what matters here, ART studs being in the 180-220,000psi range. ARP's studs are undercut.. I don't know why they do that, but lets say the 12mm is undercut to 10mm and the 11mm undercut to 9.17mm. Using 180,000psi, the tensile strength of the 12mm stud where it's undercut is 6980lbs, the 11mm studs is 5860lbs, an increase of 19% over 11mm studs.

If you want to figure out the actual force the stud is torqued to, it would have to do with the tangent of the slope of the thread. Add that to the peak cylinder pressures and divide by the studs around that cylinder and you get the max force applied to the studs. Multiply that difference by the elasticity, given their preload and you find out how much they stretch. If that's greater than the amount the head gasket can expand, you leak coolant. Fiber would typically just blow at that point as it's not held together by being squished between the head and block.
But I don't feel like figuring all that out right now 

It could be that I'm looking at the inch rate for springs, which varies with the 4th power.
Loading with the 3rd power, so is it  torsion, and thus tension with the square of the radius? I stand corrected

[pyro7890]

thanks every body i love this site and also love my diesel

[Quantum TD]

thanks every body i love this site and also love my diesel

Did you fix the leak? If so, how?

[pyro7890]

have not tried more torque yet but will post results