TR4/4A Broken Cylinder Head Stud

[RJS]

Hi

So, some of you may have seen my post about a week ago re Head Leaking Coolant after Cooling System Flush
https://www.britishcarforum.com/bcf/showthread.php?108056-Head-Leaking-Coolant-after-Coolant-Flush

I found the problem. Broken left rear cylinder head stud. See attached photos. Apparently it snapped right where the threads enter the block. It was as loose as loose could be - just floating there in place.

So, I'll definitely have to pull the head in the spring. Look at the photos too - it doesn't exactly look like a recent break (would you agree?) - kinda odd. So the question is how long has it actually been this way?? And in a strange way, I am actually somewhat relieved this wasn't caused by my "cooling system flush" and that it wasn't a head gasket failure.

Earlier today when I first discovered the head stud twirling with no resistance I was really scared that it had stripped in the block. That would have been a nightmare to drill and tap a size larger. This won't be simple but, at least I am pretty sure I can extract it and simply insert a new stud. My understanding is that head studs are only supposed to go in finger tight. If that is true, then maybe it will come out without a huge battle.

I'll be soaking the manifold nuts weekly for the next two months in prep for removing the head (the car is now stored for the winter). They are extremely rusted and I anticipate big problems getting those off. Probably bigger pain than removing the head itself.

Appreciate any thoughts you may have on extracting that stud once I get in there - or any other comments or ideas you may have on this problem.

Bob

PS: coincidentally, in June 2006 a so called "British" mechanic said he removed & replaced the head due to a so called "oil leak" (which I had never noticed). The invoice said he planed the head and installed a new head gasket. I never requested this work and he charged me $500 (not happy!).

Then in the summer of 2007 (~500-700 miles later) I first noticed oil leaks coming from literally everywhere – timing chain cover, oil filter housing, fuel pump, oil pan, valve cover, even the bolts attaching the ignition coil to the engine block! I spent years fiddling with the PCV system and improved the venting on the motor. Although the leaks are not as bad, I still to this day have leaks from the timing chain cover, oil pan and rear main seal. Now I wonder if that mechanic cracked the head stud back then and somehow (not sure how) that was allowing combustion gases to pressurize the crankcase all these years??? Does that sound possible? If so, then I am kinda encouraged that this repair may also solve my oil leaks.

 

[Rubicon]

If you have access to your car during the winter and can do a bit of maintenance, clean all the threads of the bolts that you can see with a wire brush and keep adding oil. As well if you can heat up the nuts/studs and spray oil on them when hot, lots of smoke will be made/small fire if too much oil added, but the heating and cooling will brake the rust and and oil will creep between the threads.

 

[Geo Hahn]

I once broke a head stud on my Fiat but the end was jagged. I was able to put the broken bit back in, engaged the jagged ends and twirl the lower end of the stud right out (a magnet finished the extraction). You do not have a jagged end so that won't work but my point is that yes, you may find that the remains of that stud are not tight and hopefully removal will be straight forward. You might even be able to Dremel a slot in the remaining piece and take it out with a screwdriver. You'll know much more once the head is off.

 

[2long]

Not sure what you mean by finger tight head studs - they are torqued at a pretty high number (95 -100 ft/lb or something similar). If the remains of the broken stud are above the deck of the block, there are lots of techniques such as welding on a nut to the stump of the stud sticking out. If the top of the broken stud is below the deck of the block, you should be very careful and not jump right to some kind of easy out extractor, because those can create bigger problems if not used correctly.

Dan

 

[Geo Hahn]

The nuts are certainly torqued to 100+ ft/lbs - but I am under the impression that the studs are simply threaded into position.

Of course that old enemy corrosion may have been at work making a stud hard to remove.

You are quite right that the EZ Out is something to be wary of as breaking one off in a stud creates a much bigger problem.

 

[DavidApp]

Apply lots of penetrating oil, you can put some down the hole now to start the process.
When the head is off if it can't be unscrewed easily by cutting a slot or turning it with a center punch you can carefully mark the center of the stud center punch it then drill it out using progressively bigger drills bits till you are just smaller than the thread diameter. Using a Left hand twist drill will help, with luck it will just unscrew as you drill.
Be careful that you are centered as you do not want to damage the cylinder block thread.

Good luck.

David

 

[RJS]

Thanks Gents,

Appreciate all the ideas. I will be hitting all the nuts and studs with penetrating oil daily for the next two months. I'll just have to wait until the head comes off to further assess my options on removing the broken stud - hopefully it is proud of the block and not down in the hole. And yes, I admit although the studs are inserted finger tight, I failed to acknowledge the head nut is subsequently torqued to 100 lbs-ft. Likely that and 20 yrs of corrosion will challenge me!

Bob

 

[TR-3rg]

Hi,

I second a LH drill bit. I worked my way thru college in an engine shop. We used a LH drill bit all the time for broke exhaust manifold bolts. Grainger or MMC has them. You might need a drill press to get the pressure but you can rent a portable one with a magnetic base.

RG

 

[TBU_Triumph]

Hi Bob,

Here are a few thoughts on the various responses and your original post.

• There are 3 tricks I use with corroded threaded joints that greatly improve my chances of getting things apart without breaking anything.
  • Use 6 point sockets with as heavy a wall as you can fit on the fastener.
  • Make the first movement to tighten the joint! You will be surprised how many times the fastener will move and expose a little bit of non-corroded thread that you can spray with penetrating oil.
  • Then try to loosen the joint no more than a quarter turn. Retighten it to snug, spray it and loosen again trying to get to a half turn. Repeat this sequence taking the joint further apart each time. (Note: I am not a proponent for using the biggest impact wrench you have unless you know you are going to scrap the parts.)
• Yes, studs are to be installed just slightly beyond finger tight. Stud threads are put under tension when the nut it torqued on the other threaded end. Based on the pictures you included it looks like the failure could be due to the studs being over-tightened into the block.
• I strongly agree with the advice to not use an insert type extractor. I have not had good experiences with them.
  • By design an extractor adds to the problem because it expands the broken portion. As it screws deeper into the part the taper wedges things even more.
  • After you break one off they are impossible to drill because they are so hard.
• Yes, get a left handed drill set. Start small and work your way up in size. Do everything you can to get the center punch as centered as you can and then drill straight. If the top of the broken stud is below the surface use a short piece of tubing (or a piece of round stock that has been centered drill on a lath) as a guide to help center the punch. The OD needs to be about the size of the minor diameter of the threads.

It looks to me like you might have caught a little bit of luck. Based on your pictures I think the broken stud in one of the shorter ones so you can at least get to the top of the hole when the head is off.

Hope it goes well. Patience is key!

Rusty

 

[RJS]

Rusty,
Thanks, these are all really good ideas and greatly appreciated. I have made notes of the advice here as the car is stored for the winter until March. In the meantime, I am hitting all the nuts on the head, manifolds and downpipe with penetrant every day.

The head is still on the car but, by my measurements 3/4" of stud remains and it is 3/16" below the deck of the block. In addition to the above advice, what is anyone's thoughts on applying heat with a torch or cold with something like CRC Freeze Off - to either the side of the block or the broken stud itself? Last thing I want to do is warp or crack the block.

Thanks

Bob

 

[RJS]

Hi,

Some of you may have seen my other post about removing the cylinder head. Anyway, I like to close the loop on threads like this. Cylinder head came off this morning. Broken stud was the right, rear-most stud. It broke off with about 3/4" of the stud stuck about 3/16" below the deck of the block. I was worried all winter about how I was going to get this out.

Despite all my worst fears, it came out in about 15 minutes with a few light taps of a center punch with a hammer. I simply caught the edge of it and it spun right out! Holly cow I was lucky!.

Next is to clean everything up and reassemble with hardened ARP studs!

Bob