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Cracked head; Hairline crack inbetween valves
Topic Started: Nov 25 2011, 05:01 PM (2,732 Views)
obaja
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Diesel Power

Here we go again. So I rebuilt my engine about a year ago. 15,000 miles since rebuilt(rings,rod bearings, 3tech ss exhaust valves, valve seals, head gasket). I noticed that during cold starts engine would run on 2 cylinders for about 5 seconds then the 3rd would kick in. Pulled head and number 1 cylinder was using coolant. APEX headgasket had just started to crack between number 1 and 2 cylinder which is why it used water.

So upon further inspection i noticed a Hairline crack in between the intake and exhaust valve on cylinder 1. It is tiny and does not go down to the valve seats. Is this a problem?

Second question; Is this too much oil around the intake valves?

I did not replace the valve guides only the valve seals and wonder if the guides are shot...

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Memphis metro


Did you reuse your headbolts or buy new ones?
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obaja
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Diesel Power

Brand new 3 tech head bolts. I checked the torque before i pulled the head today and they were right on. Cleaned head and block immaculately before putting it together last year. I also checked both with straight edge last year for unevenness and both checked out ok.
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Tofuball
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Strange Mechanic

Of the few heads I've taken apart so far, the valve guides have been pretty toasty. They're easy to check.

I doubt the hairline fracture would continue into the valve seat as the valve seat is actually a steel insert.

Is your head warped now? That's also easy to check.
Edited by Tofuball, Nov 25 2011, 08:12 PM.
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obaja
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Diesel Power

toasty as in toasted-no good? I will get a straight edge from work tomorrow and check the head and block to see if they're warped.
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mwebb
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FOG

in the older VW diesel engines that pre dated the TDi engines
cracks like that were common and it was acceptable to re use the cyl head

it was also common for those who did not know to re use the original bolts which were not TTY bolts
the head gaskets would fail quickly

new TTY bolts always had to be used
you can not check the torque of a TTY bolt after it is installed , which leads me to believe
that you did not use TTY bolts

which has been proven many times
to be a
bad idea

if MLS head gaskets are available , they will outlast anything else

TTY = torque to yield
MLS = multiple layer steel
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JoeBob
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Why you Mutt!

Maybe you can just peen the crack shut, re-lap the valve seats and run with it. Worked for my dad on a '37 Chevy.

When he told me he had done this to the aforementioned Chevy, which had been driven w/o coolant and pulling a trailer from Death Valley to LA, I thought it to be the epitome of piracy. Some years later, I discovered that there were power tools made to perform this very task...apparently it is/was an accepted method of repairing cracked heads.
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t3ragtop
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Turbo3 and Twincam Tweaker

you can have success peening a crack in a steel head, not so much with aluminum.
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obaja
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Diesel Power

mwebb
Nov 26 2011, 01:10 AM
in the older VW diesel engines that pre dated the TDi engines
cracks like that were common and it was acceptable to re use the cyl head

it was also common for those who did not know to re use the original bolts which were not TTY bolts
the head gaskets would fail quickly

new TTY bolts always had to be used
you can not check the torque of a TTY bolt after it is installed , which leads me to believe
that you did not use TTY bolts

which has been proven many times
to be a
bad idea

if MLS head gaskets are available , they will outlast anything else

TTY = torque to yield
MLS = multiple layer steel
mwebb. I used 3techs bolts which are not tty bolts. So you're saying it these are not better than the stretchy tty bolts?

I will look for a mls gasket, I know thats what the exhaust manifold gasket is made out of and my mercedes diesel engine uses these mls gaskets and its bulletproof.
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Memphis metro


http://www.engineproblem.com/torque.htm
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t3ragtop
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Turbo3 and Twincam Tweaker

there's no mls head gasket available for the g10. believe me, i've looked for years. you are right, however, that some g10 exhaust gaskets (the good ones from the factory) are mls type.

mrwebb used an old vw to illustrate the acceptability of putting a cracked head back into service. he and i will disagree on one point - i've run a felpro carbon gasket and suprf1y's re-usable head bolts over-torqued by 10% (59.4 ft/lbs instead of 54 ft/lbs) on a turbo3 that has stayed together for 4 years and which will no doubt last another 4 or more.

in his convoluted statement, his point is that if you use tty bolts, you have to use new ones every time or face the possibility of failure. with suprf1y's bolts, you can re-use them as they will not stretch and deform at the applicable torque rating. from that standpoint, the 3 tech performance head bolts can be a bargain as they don't require replacement every time you pull the head like the oem tty bolts. you'd be more likely to pull the threads out of the aluminum alloy block before those head bolts reached their failure point.
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nwgeo


I have had APEX gaskets fail. I have not had a Felpro fail. Just me.
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obaja
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Diesel Power

nwgeo
Nov 26 2011, 10:23 PM
I have had APEX gaskets fail. I have not had a Felpro fail. Just me. Good info t3ragtop. Does felpro make more than one gasket for the g10? a carbon and a ____?
Thank you, that's what I wanted to hear. I was going to go Felpro anyways and you have just doubled my trust in them. I know they are a big name in gaskets especially in the v8 world.
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obaja
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Diesel Power

Slapped in a felpro headgasket, put it all back together, and it runs like new. Thousand miles on it so far and no problems. Torqued the bolts to 57 foot pounds which is more than the book says. Ran the engine to full temperature then torqued all the bolts again and the 2 bolts at the front of the engine at cylinder 1 turned 1/16th of a turn each. All other 6 bolts were right on torque. Hmmm, interesting considering the gasket blew on cylinder 1.
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Cobrajet25
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mwebb
Nov 26 2011, 01:10 AM
in the older VW diesel engines that pre dated the TDi engines
cracks like that were common and it was acceptable to re use the cyl head
:gp It's really unusual to find an old 1.5-1.6 VW diesel head that ISN'T cracked between the valves. Or cracked at the injector mounting holes...

Stupid VWs. :shit

I think you are okay with that tiny hairline.
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