Looking for writeup to replace head gaskets on s4
#31
Rennlist Member
Dawid,
First of all many congratulations on successful removal of the heads- well done! Engine out or Ruptured Russian technique?
Now we need to find a photography course/tutor near you!
From what I can see of your photos you have dodged a bullet in the nick of time pretty much as expected. Please post some photos of the heads without gaskets and preferably in focus and with correct exposure. It is clear to me that your gaskets have been eaten away in typical fashion and now we need to see whether the heads have taken much in the way of attrition. The block side looks to be in excellent condition to me but I will defer that one to our more knowledgeable friends as they wake up. As of your post I cannot see any evidence of a head gasket leak as yet but the photos really need more clarity to make a good interpretation.
Your comment about the bolts was also interesting. The crack you heard was most probably and quite literally a crack taking place. In his earlier post Greg commented about hydrogen embrittlement and asked if there was a remedy. The simple answer is both yes and no. Assuming the bolts have been embrittled by hydrogen from the corrosion process that was taking place, were it possible to get the bolts out without torquing them then cooking them at 200C for half an hour or so would get the hydrogen out and reverse the process. However, in the process of releasing them the embrittled condition would leave them in such a state that in the process of applying breakaway torque the bolts will [I suspect] have quite literally "cracked" and probably caused the "cracking noise" you heard.
First of all many congratulations on successful removal of the heads- well done! Engine out or Ruptured Russian technique?
Now we need to find a photography course/tutor near you!
From what I can see of your photos you have dodged a bullet in the nick of time pretty much as expected. Please post some photos of the heads without gaskets and preferably in focus and with correct exposure. It is clear to me that your gaskets have been eaten away in typical fashion and now we need to see whether the heads have taken much in the way of attrition. The block side looks to be in excellent condition to me but I will defer that one to our more knowledgeable friends as they wake up. As of your post I cannot see any evidence of a head gasket leak as yet but the photos really need more clarity to make a good interpretation.
Your comment about the bolts was also interesting. The crack you heard was most probably and quite literally a crack taking place. In his earlier post Greg commented about hydrogen embrittlement and asked if there was a remedy. The simple answer is both yes and no. Assuming the bolts have been embrittled by hydrogen from the corrosion process that was taking place, were it possible to get the bolts out without torquing them then cooking them at 200C for half an hour or so would get the hydrogen out and reverse the process. However, in the process of releasing them the embrittled condition would leave them in such a state that in the process of applying breakaway torque the bolts will [I suspect] have quite literally "cracked" and probably caused the "cracking noise" you heard.
#32
Archive Gatekeeper
Rennlist Member
Rennlist Member
It's an audible crack, not a literal one. You load up on a 40" breaker bar to loosen a head bolt, and the loaded up force suddenly overcomes the resistance to turning and the bolt rotates quickly, making a cracking noise that you can feel through the bar. Not sure whether it's
A. the dried crud sitting around the top of the threaded portion that's fracturing apart,
B. the bolt is twisted from the force of undoing it and as the threaded portion turns suddenly it makes a grating noise, or
C. you're hearing whatever corrosion there is between the bolt and the block suddenly let go and allow the bolt to rotate.
Or D, none of the above. Dunno.
A. the dried crud sitting around the top of the threaded portion that's fracturing apart,
B. the bolt is twisted from the force of undoing it and as the threaded portion turns suddenly it makes a grating noise, or
C. you're hearing whatever corrosion there is between the bolt and the block suddenly let go and allow the bolt to rotate.
Or D, none of the above. Dunno.
#33
Three Wheelin'
The top of the bores on some of the cylinders appear to have corrosion damage (like #4 & #8). Have you cleaned it up yet to see?
Last edited by namasgt; 09-03-2021 at 03:47 PM.
#34
Former Vendor
(Have them strip the heads, clean the heads, and then pressure test them.)
Worth mentioning, since the cracking occurs right at the edge of the 90 degree counter cut where the head washers sit, these heads can also crack when they are re-installed and tightened.
(Cracking during re-installation is more common when people not familiar with these engines fail to replace the head bolts and the resulting pressure on the head is higher due to the old bolts not stretching properly.)
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545svk (09-03-2021)
#35
Burning Brakes
Thread Starter
#37
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Thanks 545svk for this thread.
As my car (like may others) will probably need this someday, it gives me some confidence to do it myself (with some help from friends too of course!).
Keep posting.
Keep up the good work!
As my car (like may others) will probably need this someday, it gives me some confidence to do it myself (with some help from friends too of course!).
Keep posting.
Keep up the good work!
#38
Rennlist Member