What's the deal with Stretch Bolts

hardflex · 11-07-2009, 08:56 AM

I replaced the head gaskets on my V6 German engineered Mazda PU motor for the 2nd time. The heads were inspected by a machine shop and milled flat. I put a new set of stretch bolts as recommendedand then Torqued them to specs. Have since put about 3k miles on it, maybe more.

It seems to be seeping a small amount of coolant into the cyl chambers overnight. I get water fouled plugs then when they dry out and fire lots of steam out the exhaust for a brief period. Then it seems to dry out and works fine when the engine is warm. Coolant loss is about a 1 or 2 quarts a week.

I'm from the old school that retorqued the cyl heads after a break in period. I know the new school say no. But I feel like they're not tight enough to seal the head gasket at cold head temperatures.

I used oil as my lubricant in tightening the head bolts.

If I 'retorque' the head, should I replace the head bolts again, or just tighten the existing ones.

Or, is it nothing to worry about and just drive it and add water.

Any advice is appreciated.

cbush · 11-07-2009, 09:23 AM

I have re-tightened stretch bolts before with no ill effects. Given your leak, doesn't seem like you have much to lose. It that doesn't work and you have to take it off and use a new gasket, I would go with new bolts.

sewell94 · 11-07-2009, 09:24 AM

You shouldn't need to retorque the head bolts, but if you do i would just reuse the ones you have. People reuse head bolts all the time. This doesn't sound like your issue though. You check the block to see if it was warped??

porsche4life · porsche4life's Garage

Its a Mazda.... They have HG issues... Just live with it

Mrmerlin · 11-07-2009, 11:23 AM

add some Barr stop leak and hope the leak stops, if you have coolant leaking into the cylinders it will be only a matter of time before one of the cylinders fills up with enough liquid to cause the rod/piston/ cylinder/ or head to be damaged beyond repair.. ( think hydrolock)

T77911S · 11-09-2009, 05:28 AM

i would not losen them, just check them.

are they a torque then turn a certain number of degrees or just torque only?

try some copper coat on them next time. check for carcked cylinder.

1990C4S · 11-09-2009, 01:28 PM

I do not think it is something to ignore. A head should not leak.

If the head bolts were 'low torque' and then cranked XX degrees then a bit of oil on the threads is fine. If they are just high torque and done then oil is not a good idea, I think they would typically call for a dry installation in that case. Either way, they are in now so forget about how you did it.

I would re-torque them at this point, maybe 20 degrees if you can?

I also agree with the Barrs additive suggestion. The little blue bottle with the black walnut shell liquid. Straight into the rad, not the reservoir.

hardflex · 06:30 PM

the spec on the head bolts were 55 lbs torque then and additional 90 degrees tighter. As this was the 2nd time I've done this job, I used copper coat at the recommendation of the machine shop. I was really careful to try to do everything necessary to insure this job would be done right and last.

I know it could be the block and not the head that's not flat.

The first time I did this job I reused the head bolts, and it didn't last long at all, like 2 weeks. When I tore it down again I used new stretch bolts and it worked fine for a while, 10k miles or so. The engine got pretty hot and caused the gasket to fail this time, much worse water usage than I'm seeing now.

This truck just turned 370k but it's still pretty solid if I can keep the engine working. I only need a truck sparingly and so don't need another.

In the old days to retorque, I'd loosen slightly then retighten the bolt to spec. What I'm hearing here is don't loosen, just tighten. Should I just just tighten them down to 85 or 90 lbs like old v8's and let it go?

T77911S · 11-10-2009, 03:31 AM

not sure what i would if the spec is lbs plus 90. i dont know if there is a conversion to just torque. maybe contact the manufacturer of the bolts.

if there is something wrong with the block, you are just wasting your time. cast iron block i assume?

take the head off the bad side and check for a cracked sleeve. if nothing, switch heads from side to side.
my brother had the same thing going on with his range rover. after he put the heads back on he had a leak, then it stopped. he has been driving it ever since. he had the heads off a few times but i dont remember what all he did. i know he used the copper coat and he had someone come look at the block to make sure it was ok.

1990C4S · 11-10-2009, 05:11 AM

Quote:

Originally Posted by hardflex

In the old days to retorque, I'd loosen slightly then retighten the bolt to spec. What I'm hearing here is don't loosen, just tighten. Should I just just tighten them down to 85 or 90 lbs like old v8's and let it go?

The bolts would/could end up past their yield point if you loosen and then re-torque, don't do that. Just tighten or get new bolts and start over.

Personally, I do not think you can fix this issue by tightening the bolts. I suspect there is a deeper issue.

I know some people have had success with two head gaskets. A last gasp I guess.

cashflyer · 06:58 AM

Some torqued bolts are torqued dry.

Torque on a dry thread is not the same as torque on a lubed thread, and you can easily over-torque and overstretch the bolt. Also, lube will allow the torque to back off gradually with exposure to heat cycles and vibration.

Does MAZDA suggest using lube on them... or just something y'all decided was a good idea?

Google "dry torque vs wet torque" for more discussions.

1990C4S · 11-10-2009, 11:35 AM

Lube is less of an issue when you got to a relativley low set point and then 90 degrees. Still an issue though, I agree.

I would rather see Loctite used as a lube than oil.

Maybe a Mazda forum will help you out on the best procedure here? Specific vs. general knowledge (and guesses)...

island911 · 11-10-2009, 12:41 PM

Quote:

Originally Posted by hardflex

....
I'm from the old school that retorqued the cyl heads after a break in period. I know the new school say no. But I feel like they're not tight enough to seal the head gasket at cold head temperatures.

If I 'retorque' the head, should I replace the head bolts again, or just tighten the existing ones.
.

If you reuse, then the procedure for torquing changes. ...because the 'slack' has been stretched out of the bolt.

I've "over" torqued head bolts before - back when I was too poor to buy new, and too ignorant about the torque + angle approach -- nothing bad happened. That was w/ alum head on a cast iron block. (tough to pull threads.)

Doubling head gaskets will cause more problems, not less.