2nd Blown Head Gasket

[pressonregardless]

Alright....Grrrr. I can't believe my luck, apparently I have a Blown Head Gasket.....again !!

Not happy, I posted last April 2014 (in General Maintenance) about my findings when I re-torqued the head after a few drives, or about 4 trips and 70-80 miles and found about 4 head bolts at 40 ftlbs. I checked again in mid-summer of 2014 and all seemed tight. Yesterday, March 2015, I made a casual trip around town and noticed my exhaust tone (sound) started to change at the last two stop signs before my house. Sure enough, backing into the driveway, saw a big puff of white smoke.....coolant for sure! FYI, I have never had the RPM touch 5K, but obviously over 4K on the highway, not that it matters.

What gives??? I had the head redone by a long term speed shop and the 60year old owner recognized the head as I walked it in. I have had help from Ramzi at Auto-Ricambi and purchased both gaskets from them. I cleaned the deck and do not coat the Head Gaskets with anything. Torque sequence from the manual inside to out, from memory I think first pass was 45 ftlb, then 61 with a Craftsman Beam Type Torque Wrench. (Rental of click type from local O'Reilly's proved to be out of calibration).

My first head gasket let go at 113K miles, between cyl 1 & 2, the next one held up about 2 months at maybe 250 miles and let go between cyl 3 & 4. This one let go 9 months later, perhaps 700 miles and approximately 25 - 30 head cycles from overnight cold.

So open to suggestions. There has got to be something I am missing. Took a few days break, as I didn't want to touch it, but will scream if Head Bolts are loosened up to 40 ftlbs again. BTW, it will be 75" and full sun today, Sunday. Thanks!

[bradartigue]

Are you re-using the head bolts? I've never heard of a bolt loosening on its own that was properly torqued before. Perhaps the bolts or the holes they are going into are in a condition where they can't hold.

[azruss]

sounds like you have gunk in the bottom of your holes or thread deteriorization at the bottom. I would go in with a flat screwdriver and scrub the bottom of the holes then blow them out. I would also take an old head bolt and grind it short until the thread taper was gone and use that to chase the threads. be careful about breaking the bolt off. i would even by an extra new head bolt and turn it into a chaser since the treads havent been compromised yet.

[pressonregardless]

Thank you for all suggestions.
To answer Brad Artigue, I am using the original head bolts.
I scrubbed the threads with a wire brush and Brake Cleaner to insure they were clean. I cannot say the thread holes were equally clean, but appeared so. When re-torquing the head after a few hundred miles, I put the beam type torque wrench on the bolts and tried a check torque and found several of them began to turn when the pointer reached about 40 - 45 ft lbs. I can't say the bolts backed off, but I was able to tighten them again to approx. 61 ft lbs.

To Azruss, I'll have to order an extra head bold and make the grind. Not sure what it will buy me, but will try any old "tricks" to stop blowing head gaskets. Open to any suggestions.

[So Cal Mark]

cleaning the bolt holes is mandatory to get accurate torque readings. You have to use a tap or thread chaser and lubricate the bolts properly. Has your torque wrench ever been calibrated? Did you check flatness of the head and block?

[RRoller123]

How do you generally clear the crap out of the bottom? Just hit it with compressed air?

[RoyBatty]

I will recommend you use the steel layered head gasket that Allisons sells.
Along with making sure your threads are cleaned, lubed and in good condition.
Good luck.
Could you have burned the last one from lean mixture or to much advance in the timing?

[TimpanogosSlim]

a bottoming tap is the preferred tool to chase head bolt threads. at least that is what is specified when installing studs.

[azruss]

A bottom tap of that size will be hard to find and very expensive. Most bottom taps do have taper on the last couple of threads. Might not be an issue as those threads were probably tapped with a bottom tap in the first place. For your purpose you just need to chase the treads, not cut new ones.

[TimpanogosSlim]

A bottom tap of that size will be hard to find and very expensive. Most bottom taps do have taper on the last couple of threads. Might not be an issue as those threads were probably tapped with a bottom tap in the first place. For your purpose you just need to chase the treads, not cut new ones.

Yeah it's the sort of job you have the machine shop do, 'cause they already spent a couple hundred bucks on a really long M10x1.25 tap.

My engine building mentor works at a machine shop that is so clean you can eat off the floor, and has been building engines there for almost 12 years. Head bolts on certain blocks, sometimes just certain head bolts on certain blocks, get dabbed with some white substance out of a tub with a Permatex logo. Sez it's "glue". Sometimes it gets used for bolts that go through a water jacket.

Dunno what the stuff is. I'm under the impression that it's not regular old thread locker, or he'd have said so. I know the subaru flat 4 blocks get some thread locker that is in excess of the red stuff. Have to heat up those head bolts with a torch to get the engine apart. He's not a fan.

[redcars]

You can get 10x1.25 taps from McMaster-Carr for $22 + shipping.

[TimpanogosSlim]

heck, you can get a whole set of metric and pipe taps and dies for that at harbor freight - but how long does it have to be? I ask because I'm actually not sure. taps with long shanks are less commonly needed thus more expensive.

[azruss]

I don't remember how deep the threads go. You may need a reduced shank tap. I would not use a cheapo chinese tap. They havent got hardening down very well and their drills and taps are brittle. You definitely dont want to break off a tap in your block.

[131]

It doesn't matter how deep the threads go, you only have to clean up deeper than the length of the bolt will engage. Any standard plug tap will be long enough, but don't buy stuff made from Taiwanese cheese.

[seabeelt]

It's a common problem to have oil and coolant leek down into the bolt holes when you pull the head. Like others have said clean the holes. I used a long screwdriver to loosen the gunk at the bottom of the hole and then used compressed air and some wd 40 to clean further and then wd 40 and some q-tips. After that I ran a head bolt up and down the hole (should use almost all of the threads on the bolt) to further clean the hole and then repeated above. Junk in the bottom of the hole will give you a false torque reading, particularly oil or coolant. As the liquid finally seeps past the threads, you lose the torque value as there is no more bottom pressure. The bottom pressure is what is giving the torque reading versus actual tightening of the two mated surfaces of the block and head.
R/