Help! cylinder head stud blown

MartinA · Post by **MartinA** » Sun Jul 05, 2015 9:56 am

Driving along in the sunshine only to hear a bang under the bonnet...I thought it maybe a stone or other solid object from the road. About half a mile later steam from bonnet vents. Pulled over, opened bonnet to find coolant in the V of the cylinder head. No hoses burst. On further inspection proved to be a snapped cylinder head stud which had been forced up and dented (made by the domed nut on the stud end) the underside of the bonnet hence the bang. The stud comes out completely and you can see where it has broken just below the start of the thread. I am no engineer so any advice appreciated...the key question for me is whether the stud blew due to water ingress in the block from corrosion in a water jacket channel which allowed water into the stud thread leading to corrosion and may explain the loss of coolant. Or is there another explanation or something I should look at? Is this an engine rebuild or could the studs be drilled out and replaced? Advice appreciated. Thanks.
Martin

Post by **1954Etype** » Sun Jul 05, 2015 10:35 am

I think l read somewhere that it can be done in situ but you need to find a specialist with the correct equipment.

Advisable to replace all the studs at this point.

We have just had an engine rebuilt with this problem.

PeterCrespin · Post by **PeterCrespin** » Sun Jul 05, 2015 10:59 am

What year is the car? Which position stud?

Please put your car info in your signature so we don't have ask supplementaries.

Pete

MartinA · Post by **MartinA** » Sun Jul 05, 2015 11:52 am

Apologies - it's a 1970 S2 OTS. the stud concerned in on the RH side looking down the engine from the rear between cylinders 2 and 3.

RogerM · Post by **RogerM** » Sun Jul 05, 2015 2:17 pm

Hi Martin,
I had exactly the same problem a few years back. On removing the head I found that the previous owner had had the same problem and put helicoils into the top of the block to repair it. Not recommended!!
I took the engine out and got Classic Car engines Ltd 08453457687 to collect it and replace all the studs with special stainless ones.
The problem is due to not having antifreeze in the water, and the studs corroding where they pass through the jacket. Only an issue on the 4.2.
Regards
Roger

RogerM · Post by **RogerM** » Sun Jul 05, 2015 2:26 pm

Hi Martin,
Just thought -- age!!
If you are a member of JEC. ( you may be able to view it even if you are not a member?) I posted an article on their Forum - E Type - Engine entitled Broken Cylinder Head Stud 4.2 Engine which has a bit more detail and some photos that may help. Posted Jan 2012.
Roger

MartinA · Post by **MartinA** » Sun Jul 05, 2015 5:33 pm

Thanks Roger - much appreciated. Will try to take a look.

BRM · Post by **BRM** » Sun Jul 05, 2015 5:43 pm

Mine is the engine which Angus mentioned. The exact same thing happened as I was driving home from passing the MoT - soon took the grin off my face ! And it came out with such force that I now have a dent in the underside of the bonnet to fix.

Brian

MartinA · Post by **MartinA** » Sun Jul 05, 2015 7:48 pm

Thanks Brian - same issue with mine...nice dent in the underside of the bonnet! Do you know if the stud passes through a water jacket cavity?
Martin

BRM · Post by **BRM** » Sun Jul 05, 2015 8:31 pm

Yes Martin. Being fairly new to E types I didn't even know what a long stud engine was until this happened. It seems the earlier engines have studs screwed into the top of the block like engines I've worked on before, but ours go right down through the water jacket into the bottom of the block.

As Angus says, if one has gone, chances are some of the others are about to go so they should all be replaced. One problem as I understand it is that they screw into blind holes so, once removed, any sludge in the bottom of the block will run into the holes. This must be cleaned out or the new one will not screw down fully. This in turn means that when you torque the head down they might bottom in the domed nuts before they are tight on the head.

Brian

MartinA · Post by **MartinA** » Sun Jul 05, 2015 9:16 pm

Sounds like a tricky job...if I have to get the engine out maybe worth getting a few other things sorted at the same time. The engine has done about 98,000 miles although was running sweetly until this.

christopher storey · Post by **christopher storey** » Mon Jul 06, 2015 9:43 am

Martin : Brian has identified most of the difficulties of stud replacement. All can be reached by removing the core plugs , but each individual stud replacement can bring its own difficulties , not least of which is that the metal of the block may have "grown" over the years so that the stud bottoms out in the hole even though the hole has been thoroughly cleaned . Therefore, on balance it is better to remove the engine to do a thorough job, and the balance is tilted even more that way in your case in that getting the broken stud end out of the thread is going to be a fiddly, difficult and time-consuming job ( and you may break more studs along the way in removing the cylinder head )

Durango2k · Post by **Durango2k** » Mon Jul 06, 2015 7:29 pm

How do you remove a rusty stud end, 8 inches down under in the block ?

Carsten

MartinA · Post by **MartinA** » Mon Jul 06, 2015 8:31 pm

Thanks for the advice Chris - engine out it is...worth doing a thorough job.

christopher storey · Post by **christopher storey** » Tue Jul 07, 2015 10:37 am

Durango2k wrote:How do you remove a rusty stud end, 8 inches down under in the block ?

Carsten

With difficulty . Some people drill the broken end and use a left hand thread extractor, but this is fraught with danger because the extractor may snap. Others weld a threaded rod to the broken end and then use two nuts on it to unscrew it, but this sounds to be a difficult proposition in this case because there is no residue of stud sticking up above the block. If neither of these work then probably taking the block to an engineering shop which has spark erosion equipment, or some very accurate long drill bits , may be the best way

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Help! cylinder head stud blown

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