Re torque fixes head gasket?

[froggy47]

I hope I'm not jumping the gun, but on Monday I retorqued the head on 95 M3 125k miles.

Was loosing coolant & getting hydrocarbons in coolant.

So far the coolant level is 100% the same level each morning cold engine.

I know the bolts are use once, but there was no downside to trying to retorque them.

I was ready to pull the head anyway.

I did not loosen (of course), just started @ 22 & went up 2 lbs each pass until I got 3 bolts to move (at 30).

Then I stopped.

I am surprised the torque spec did not go higher to get some to move. Comments?

I (maybe) have a theory that this motor should have those bolts retorqued every, say, 60k miles and maybe this will prevent a lot of HG replacements.

Anyone have a theory about why this seemed to work?

Remember this was a small hg leak not a full blown out one & not a catastrophic overheat.

[SPL15]

Haha, ghetto fix for sure, but it'll buy ya some time for free so can't complain with that. The science principals make sense, but the long term reliability is VERY questionable.

I did the same thing on a leaky HG on an old Mazda 626 that overheated & owned back when i was broke in kolej. If it's just a separation of the head to the gasket leak from over heating (ie warped head) then this can work... but for a cylinder to cylinder blow through or a blown hole through the gasket to coolant sleeve, etc. it most likely wont work & you risk breaking a bolt or having to timesert the head bolts if the block is Aluminum which I had to do in a bad HG in a GM northstar engine in my Caddy STS (not fun).

EDIT: & the Manufacturer knows (at least should know) that the HG compresses a bit & should have taken this into account with the original torque specs. HG bolts shouldnt need to be retorqued, The two HG's I've replaced before all had bolts that were scary tight (since I was loosening, I didnt have a torque wrench on em though ). The Northstar engine dethreaded 2 bolt holes in the block when I removed the head. Also I hoped you torqued the head bolts in a criss cross pattern to avoid further warping your head. My guess is that your head got warped someway somehow which let a tiny space develop between the gasket & head. Tightening the head bolts closes this down buy squishing the gasket to fill the gap, but it is not optimal & far from reliable in my opinion. There is a good reason why it is sooooo important to resurface a head when replacing a HG.

[MasterKwan]

I (maybe) have a theory that this motor should have those bolts retorqued every, say, 60k miles and maybe this will prevent a lot of HG replacements.

I suspect the bolts stretched. Stretched head bolts are common problem on Subys when you turn the boost up. In the case of overheating, I suspect the bolts get stretched beyond their elastic state and never fully return to the old length. I wouldn't assume anything. You might get another 60K miles out of it or it might last forever.

[Mad Dog 20/20]

Good for you. ANYTHING beats a full HG job. I suspect something WAS up with the bolts on your motor. The torque on them should be the equivalent of about 130 lb/ft+, IIRC. No way they should have moved w/ 30 lbs. RU sure this was the original HG?

[froggy47]

Thanks guys,

It's sort of crazy that I got 3 to move @ 30 lbs.

The water level was a little down today 1 week out, about 3/4 inch down from my start mark, but I do not expect that the cold water level will EXACTLY return to the same level mark every morning.

If it stays within a range of say 1-2 inches on the bottle I will leave it alone.

Sometimes it's up a little higher in the morning (cold)

I would still like to know what the torque ends up at after the +90 +90 thing if anyone every checked it.

I don't know if it's original HG but the motor looks extremely stock & like no one has ever had it apart. Yes, I used the factory pattern to tighten each pass.

I might even retorque it again to a higher spec if a small leak still appears to be present.

Anyone know in general on other make alum head cars what the torque spec is? Over 100 seems pretty high, but I don't know.

[MasterKwan]

If I was you, I'd loosen them one at a time, in order and tighten to factory spec.

[dizzythree]

I'd replace the bolts with ARP hardware and call it a day. You can do this without pulling the head or the cams if you know what you're doing.

[froggy47]

I looked up the torque spec on my Z06 and it was 22 ft lbs +90 +90

You would think that somebody was curious as to what +90 +90 adds to the 22?

If I was you, I'd loosen them one at a time, in order and tighten to factory spec.

If I were going to think about loosening, I would replace for sure.

I have used arp stuff before, are their head bolts tighten to a torque spec, or the +90 +90 stuff?

[POPS M3]

I looked up the torque spec on my Z06 and it was 22 ft lbs +90 +90

You would think that somebody was curious as to what +90 +90 adds to the 22?





If I were going to think about loosening, I would replace for sure.

I have used arp stuff before, are their head bolts tighten to a torque spec, or the +90 +90 stuff?

Yep, I was curious and have measured many times. Here is what I have been seeing.

Stock bolts on M50, S50, M52 and S52: on tightening the second +90 gives 65 ft lbs +/-

Also I typically measure the loosening torque (breakaway torque) when removing the head bolts:
On engines that are not leaking -- 45 - 55 ft lbs before the bolts start loosening

On engines that have leaks: varies quite a bit but have seen a range of 20 ft lbs to 40 ft lbs.

Engines that have been overheated are ususlly the lowest.

Ken

[froggy47]

Thank you VERY much. That seems to make common sense. Will be checking water level once a week now & if I see smallish loss I may go in again & snug them once more.

[fun2drive]

Doing the 90-90 after initial 22 I would have to guess but 130 ft pounds sound right to me. A lot of force to apply to an 18" rachet.
Breaking loose the head bolts initially I would guess was about 45-50 pounds too again guessing since I don't punish my Mac torque wrench for those applications.

[froggy47]

I am getting a really wide range of numbers, let's limit this to no "guesses" & only post if you have checked the torque spec after the +90 +90 in some way or another and stock bolts.

Thanks.

[MasterKwan]

65 sounds about right to me. Everyone here is just guessing though since, you're not supposed to use torque in the first place. It's a 1/2 assed repair in the first place so, a 1/2 assed torque is probably good enough. If you wanted to fix this the right way well, we wouldn't be here right?

[m2pc]

Good for you. ANYTHING beats a full HG job. I suspect something WAS up with the bolts on your motor. The torque on them should be the equivalent of about 130 lb/ft+, IIRC. No way they should have moved w/ 30 lbs. RU sure this was the original HG?

+1 on that... even if you are able to put this off for a few months, all the power to you!

My dad has a classic car (1965 Chevelle) that was leaking coolant up the ARP studs in his small-block engine.

My brother replaced them with regular head bolts without removing the head, and as long as it's done carefully and one-at-a-time, it should be OK.

[froggy47]

Thanks guys, I week out the water level is in about a 1 inch range every morning on the cold engine. I am cautiously optomistic.

If you have a FINAL torque spec (not a wild azz guess) please post.

[bluptgm3]

BMW head bolts are 'torque to yeild', meaning that after the initial factory torque setting the bolts are rotated an additional number of degrees that raises the torque setting, however this also stretches the bolt. At this point the metalic properties of the bolt exhibit the highest tensil strength.
These bolts cannot be re-torqued (in theory) due to the fact that they have stretched (and really started down the path to failure) and as additional force is applied to them they stretch further....and eventially fail.




Some aftermarket Connecting Rod bolts are often measured for length to confirm stretch ensuring propoer pre-load of the joint.

[Mad Dog 20/20]

Thanks guys, I week out the water level is in about a 1 inch range every morning on the cold engine. I am cautiously optomistic.

If you have a FINAL torque spec (not a wild azz guess) please post.

If you search, you will find the "final torque spec". I am almost positive mine were 130 lb/ft. I used a 1/2" techangle wrench, which measures both angle and trq. Even if my memory is faulty, I know had to crank on it pretty hard during the final 90 degree turn - much harder than I do on a set of lug nuts, so I know its easily more than 80 lb/ft.

Also keep in mind that the head bolts/washers are lubed - not dry. So the first 22 lb/ft is likely more like 35+ lb/ft on a dry fastener. Then turnig it another 180 degrees = a lot of torque.

Play around w/ a lug bolt. Tighten it to 40 lb/ft, and then to 80 lb/ft, and see how many degrees it takes to generate the additional 40 lb/ft. It aint a whole lot. Now, that's with a non-stretch fastner. With the head bolts, some of that tightening arc is not increasing torque, but is simply stretching the bolt. If it did not stretch, the torque would be truly HUGE w/ a 180 degree arc.

[froggy47]

If I got 3 bolts to move @ 30, then, those 3 and maybe more a still seriously under torqued.

Would you agree?

[Mad Dog 20/20]

If I got 3 bolts to move @ 30, then, those 3 and maybe more a still seriously under torqued.

Would you agree?

Yes, but its all guesswork, at this point, in terms of trying to get them torqued to proper spec. The bolts are already stretched (I guess?), they are no longer lubed. Who knows how much more stretch they have in them, if any? Lots of variables. I would leave them alone, for now. If symptoms return, then I'd try new bolts.

I'd love to see somebody successfully put in new bolts while leaving the head and HG on. The superior clamping power of ARP 2000's would prolly cure many of the mild HG issues we see on these motors.

[Chokingdogs]

BMW head bolts are 'torque to yeild', meaning that after the initial factory torque setting the bolts are rotated an additional number of degrees that raises the torque setting, however this also stretches the bolt. At this point the metalic properties of the bolt exhibit the highest tensil strength.
These bolts cannot be re-torqued (in theory) due to the fact that they have stretched (and really started down the path to failure) and as additional force is applied to them they stretch further....and eventially fail.




Some aftermarket Connecting Rod bolts are often measured for length to confirm stretch ensuring propoer pre-load of the joint.

I was gonna say...I thought I recall reading where you torque them in stages, then use an angle gauge for final a final "torque" of 90*.

Once you've done that, they're "done", should not be "retorqued", as you're now living on borrowed time.

RE: ARP bolts, unless they're different for these cars than they are for american V8s, they sometimes have pretty specific instructions as to how they need to be torqued. They also, usually, spec out a specific thread lubricant to use when tightening, and IIRC, 5 cycles of "torque then un-torque" before you make a final tightening.

For the guy with the leaky Chevy head bolts.... not enough sealant on the bolts that go into the water jackets.....

[E36BMW3series]

Thanks guys, I week out the water level is in about a 1 inch range every morning on the cold engine. I am cautiously optomistic.

If you have a FINAL torque spec (not a wild azz guess) please post.

I really should know this. My angle tech torque wrench spit out the final torque number after it indicated a 90* rotation. I want to say the final was between 130-135 on all the bolts, but I know it was 120-150.

If it were me and I thought this would work I'd go buy some new bolts. Like 30 bucks maybe. Drop them in and re-torque them to factory specs. I had an external only oil leak and I honestly think this might have fixed my problem. I didn't see any obvious tears in the head gasket though.

Also you live in CA, assuming it's always warm out there I would drain all the coolant and just use distilled water. Water will evaporate out of the engine if it gets in there. Coolant is a little harder to get out. From what I understand coolant doesn't help it cool any better, doesn't prevent it from boiling, just prevents it from freezing, which isn't a problem. (Someone please correct me if I'm wrong)

[froggy47]

The coolant RAISES the bp also. If water boils @ 212f then 50/50 coolant is 240 or so & the cooling sys pressure helps raise bp also.

Yes, but its all guesswork, at this point, in terms of trying to get them torqued to proper spec. The bolts are already stretched (I guess?), they are no longer lubed. Who knows how much more stretch they have in them, if any? Lots of variables. I would leave them alone, for now. If symptoms return, then I'd try new bolts.

I'd love to see somebody successfully put in new bolts while leaving the head and HG on. The superior clamping power of ARP 2000's would prolly cure many of the mild HG issues we see on these motors.

How do the ARP "clamp better"? I know they are stronger (like their wheel lugs vs oem).

[Mad Dog 20/20]

The coolant RAISES the bp also. If water boils @ 212f then 50/50 coolant is 240 or so & the cooling sys pressure helps raise bp also.



How do the ARP "clamp better"? I know they are stronger (like their wheel lugs vs oem).

There is no practical benefit to running coolant in an S52, other than its anti-freeze properties. Race cars routinely run straight water.

The ARP 2000's are spec'd for much more torque than the OE bolts.

[POPS M3]

I have measured the torque on the second +90 and stock bolts --many times. They will come to about 65 ft lbs at the end of the second +90. These bolts are torque to yeild and you use them once. the yeilding is done while doing the second +90.

If you even think about 120 ft lbs on these stock bolts you will break them. Or you will strech them and stretch them and stretch them etc.

The new ARP bolts are torque to 32 ft lbs then +90 and a second +90. The first +90 gives you about 80 ft lbs and second +90 will put you in the 112 - 120 ft lbs range. But these are special alloy studs. Not the stretch to yeild stock bolts. Special thread design, special lubricant and special nerve to put 120 ft lbs on a 10mm bolt/nut.

If you are not running FI stock bolts are perfect.

Ken

[froggy47]

I have measured the torque on the second +90 and stock bolts --many times. They will come to about 65 ft lbs at the end of the second +90. These bolts are torque to yeild and you use them once. the yeilding is done while doing the second +90.

If you even think about 120 ft lbs on these stock bolts you will break them. Or you will strech them and stretch them and stretch them etc.

The new ARP bolts are torque to 32 ft lbs then +90 and a second +90. The first +90 gives you about 80 ft lbs and second +90 will put you in the 112 - 120 ft lbs range. But these are special alloy studs. Not the stretch to yeild stock bolts. Special thread design, special lubricant and special nerve to put 120 ft lbs on a 10mm bolt/nut.

If you are not running FI stock bolts are perfect.

Ken

I don't even put 120 on some of the suspension bolts on my z06 that are double the size of these head bolts.

Thanks.