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Discussion Starter · #1 ·
Good evening, the rocker cover and gasket has been replaced on the car approx 8,000 miles ago and has now started leaking again. This time not just in the rear corner but also from around the injector seals. I know these rocker covers are notorious for leaking! Is it common practice although not stated in any manuals to use any gasket sealant when installing.
Additionally again not in the manual but is it common to have to re torque the cover to ensure a good seal.
Is there anything that can be causing an over pressure and therefore causing this failure which I should look into.
The car is running fine but the burning oil smell in the cabin is back when the fan is on greater than the first position.
Thanks
 

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Got to say i have had loads of rocker covers off and replaced gaskets and not had one leak yet,not aware of it being notorious for having leak issues.
I have never used any sealant on them either just a good clean and new main gasket and 4 injector gaskets. Was it tightened up correctly as there’s a specific sequence?
Once torqued down properly it won’t need re torquing.
I suppose if you have got piston ring blow by causing high crank case pressure that might explain leaks appearing,

also we’re the injector copper washers replaced when rocker cover was done?
 

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Discussion Starter · #3 ·
Hi Johnny,
Thanks for getting back to me on this. The Rocker cover was replaced because the original item had a couple of hairline cracks.
The new cover is a genuine BMW item which came fitted with new gaskets from factory. I believe I correctly torqued them and in the right sequence. I followed the torque specs in the haynes manual.
From reading the newtis manual it doesn’t mention a specific sequence which I was a little bit miffed with. If you have a copy of the correct torque and sequence that I can check against I’d be very greatful.
Yeah I cleaned the injector seats and installed new copper washers. I pretty sure it’s oil sat around the injectors.
Is it possible to check for piston ring blow by?
The engine has just passed 199k miles and has had all the chains and guides replaced 20k ago and still seems very strong so I’d like to try and get to the bottom of this. I can obviously pull the rocker again and replace the gaskets but if there’s an underlying issue I can check out first I’d like to look into that.
Thanks again
 

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I don’t have the picture I used to have of the tightening sequence but it is much like cylinder head bolts. Start in middle and spiral out. I also just gradually nip them all down before going with the final 10nm torque.

so is it actually leaking still or do you think it’s the residue from previous leak causing the smell?
 

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Discussion Starter · #5 ·
10NM is the torque I applied.
It’s definitely leaking, after I replaced it it was definitely dry for nearly 8000 miles. I first realised it was potentially leaking a week ago, when the smell arrived again and on the odd occasion there would be a small haze of smoke above the bonnet if I was stopped at traffic lights. I don’t know whether to just check tighten them first or whether it’s a total strip and replace as the leak has started and will continue as it has created a path.
is over pressure a common thing on high mileage Diesel engines, that could be causing a potential over pressure?
 

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Discussion Starter · #9 ·
Hi Johnny,
I’ve just had time to run the car and lift the oil filler cap.
I started the car from cold and allowed it to idle for 5 mins. When removing the cap a small amount of smoke/steam came out. I placed my hand over the filler hole and there was a large amount of pressurised air coming out. I think if I had placed a piece of paper over it the paper would be blowing to at least 45 degrees. So is that saying I’ve got piston ring failure occurring or is it possible I have a blockage somewhere. Either way I would definitely say the top of the engine must be pressurised if you should be able to put your hand over the filler hole and find no pressure.
Thanks Stuart
 

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You will have some pressure in there but it just depends how much is deemed excessive. Back in my days in the trade we used to use a slack tube/manometer to measure crankcase pressure and compare to manufacturers figures. Not sure if that method is still used these days?
 

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Discussion Starter · #11 ·
It feels pretty strong and thumpy, as if you can feel the compression stroke forcing the air through and out the filler cap. I might look into doing a leak down test and see what that shows up.
It’s looking like internal engine wear but the leak down would help me confirm if the rings are in fact knackered.
 

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It feels pretty strong and thumpy, as if you can feel the compression stroke forcing the air through and out the filler cap. I might look into doing a leak down test and see what that shows up.
It’s looking like internal engine wear but the leak down would help me confirm if the rings are in fact knackered.
Have you looked at the ccv (crank case valve) to see if its blocked this can cause excess pressure and can cause excess oil use
 

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Discussion Starter · #14 ·
Yeah as far as I’m aware with the model n47 Rocker cover I have, the CCV part is a non serviceable item and is contained in the cover itself unlike the earlier models.
I have just purchased a leak down tester so will see what results I get back from it and let you know. I’m currently pretty sure it’s going to show an issue with the rings.
Do you know of failed pistons on this engine or is it normally the rings. I conscious that the pistons would cost a lot to replace.
Additionally can the engine be removed from the E91 with out actually removing the gearbox from the car but pulling the engine far enough forward. The Newtis manuals first step is to remove the transmission which is difficult on the drive with height clearance
 
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