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Hi all, I have been quiet on the forum, but I have been having trouble with my Bentley which I have been trying to resolve. Long story short, a problem with the immobiliser and a head gasket failure makes for an unhappy person as it is expensive job. Fortunately, I am good with a spanner (and a ratchet and occasionally hammer) so I have decided the only way forward is to do it myself. If people are interested I am happy to report on my progress, but partial tear down has already begun and so I can document the cleanup and rebuild.

Step 1 identification: So how did I find out whether I had a head failure (gasket or otherwise). Well firstly a partial strip to get good access to the plugs was required. Once good access has been achieved remove all the plugs, and turn off fuel systems to stop fuel pumping into the cylinders. I then rigged up a temporary starter allowing me to turnover the engine from the engine bay. I used a jumper on the 87a / 30 pin on the starter relay: works perfectly.

Then test each cylinder in turn.

I got 195psi on bank b, on 5,6 and 8 and 170psi on 7.

On bank a 160psi on 4,3,2 and on pot 1 50psi.

This said two things to me, bank b, seems ok, low in one pot, but within tollerance.

Bank a is low, which probably shows a head gasket. Pot 1 (the one next to the turbo charger and historically goes most readily) very low which could be warped or cracked head, piston rings, valves, or something worse!

Happy to get views on the pressures and if this is helpful, I will update as I go through.
 

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Andy, You could also introduce a dye into the coolant and checked with a UV flashlight. Not all failures result in exhaust mixing with the coolant and exploring all options is good protocol. I would highly suggest reading the blog on Robison's website regarding Turbo gasket failure. He has done many and one of the culprits is the expansion of the heads and block at different rates due to uneven heat transfer. Mr. Robison is a very intelligent person here in the states, Springfield, Mass. Part of the process is to introduce a copper sealant to the gasket for the purpose of heat transfer.
http://robisonservice.blogspot.ca/2014/10/blown-head-gaskets-in-bentley-turbo-r.html
 

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Identification step 2: So with low compression identified, off comes bank A head to take a closer look.

Before doing that, a few more bits to strip. Water coolant pipe, exhaust manifold, fuel lines and injectors. If you haven’t done so, windscreen wiper mechanism needs to be loosened, and although you don’t need to take off the turbo, it may help! I didn’t, and the head can just get past, but I can see why people would. Most of the nuts for these are 1/2 inch or 7/16. Open ended spanners will be needed for the top of the manifold to the turbo as you can’t get a socket in there. Finally, before embarking on head removal, use a 7/16 to remove the rocker and then the pushrods. Label up a box and keep these pushrods in order and the rocker in orientation. This is imperative as the rods will match up to the cups and tappets.

Although not particularly necessary, I like to follow the exact reverse of fitting, so I slackened off the bolts in accordance with the diagram below: first to half way then fully. I think the manual says you can just work outside in, if you are pressed for time. You will need a good selection of sockets and extensions for this task. 11/16 both short for the bottom ones and deep for the top ones that hold the rocker on.

Once all nuts are removed the head can be released. I was lucky as it just popped straight off, but I have done others and they needed a little encouragement with a rubber mallet! Don’t be tempted to used anything harder than this as this is an alloy head. If things are still stuck, heat can help break the seal as the head will expand quicker than the steel studs.
 

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UV dye in the coolant and use a black light!? I like that idea. I have seen Robinson’s webpage: v good and part of the reason why I thought I too would write a summary of my experience as there was not much info on the procedure.
 

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Good protocol on the tracking of pushrods and their location. Since the intake manifold comes off you may want to remove the brake pump plate and pull the lifters to soak and inspect since you're that deep into the project. If you pull the lifters you have to re-charge them will oil b4 re-installing. It never ends....
 

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Step 3 further identification. So with head off, I can start to decoke pistons and cylinders and clean the gunk off the head to check how true it is. I used a range of products available in the uk like jizer and gunk. Key to this is patience and don’t be tempted to use anything abrasive or made from steel. You definitely don’t want to damage a good head. (Pic below)

With the face clean, I then checked how true the head was with an engineers square big enough to go longitudinally across the head. Best news for me; absolutely flat and square so no damage and no visible cracks. Next onto checking the valves. I used a blow method which is the following steps. 1) spark plug reinserted, 2) bung for the injector hole to seal it, 3) bung for the inlet per chamber linked up to a pump or if you don’t mind blowing that will work too! Then a drop of engine oil is placed around the valve. When you blow into the inlet, if the valve is not seated properly, there will be bubbles of oil round the valve. The same procedure can be done with the exhaust valve using the exhaust ports.

What did I find: well all inlet valves were good except for valve 1 which was blowing. Not badly, but clearly enough. This will need to be taken apart and investigated more to whether it needs new seats or can be lapped in. When combined with a head gasket failure, this may have been the problem for low compression. More updates soon.
 

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Andy.. The block can be out of square. When it happens and you will notice condensation/coolant weeping from plugs at the block. When it warps it compromises
the liner O rings. Head warpage is more common especially when overheating occurs. I know overheating was not the problem.
 

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Yes good point. I have tested piston rings by putting oil in the cylinders and leaving it. Hasn’t disappeared so not completely shot, but I was going to maybe test more throughly with a vacuum gauge and a bung. Head flatness will be tested next once I get all the sticky stuff off!
 

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Hi Mike, it’s a 1997 28k miles Bentley azure. It spent its life in a hot country which is good as there is not the normal rust issues, but I understand that potentially comes with a higher chance of overheating. So far it has been an easyish job to fix! (Touching my wood door capping as I write)
 

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Andy,

I am impressed by what you are doing.
By the way, I am interested by the begening of the job.
I see you have the engine with water intercooler for turbo, like mine
I need to replace my rocker cover gasket, by silicon instead of cork

Could you tell me what you need to remove to be able to do that and how long doe it take ?
Plenum chamber should be removed ?
Do you have picutres of the begening ?

Thank you
 

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When the valve cover gasket is replaced with the silicone rubber update, the distance pieces and fastener seals (grommets) have to be replaced. I installed the update on my Wraith.
 

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I know Wraithman, I have all the parts ready, including aluminum grommets.
Issue is that there are many parts on the 97 cars because of the water intercooler turbo, plenum chamber....
Thanks
 

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I dabbed Permatex hi tack gasket sealant on the cover in several areas and turned it upside down and found it much easier to install since the new gasket won't fall out.
aluminum grommets. you mean new grommets for the valve cover fasteners?
 

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Sorry my english is far from yours.
I was talking about washer joint XB 1079 R just under the bolt to screw the cover
 
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