Use of Copper Gasket Spray On Cylinder Head

Use of Copper Gasket Spray On Cylinder Head

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Leptons

Original Poster:

5,113 posts

175 months

Wednesday 26th July 2017
quotequote all
I'm in the process of replacing the head gasket on my car (it's a 328i Sport). It's my first head gasket change actually having done pretty much every other type of repair! The head is off at the engineers getting skimmed and pressure tested.

I've stumbled across a few posts online about coating the block face with various things to aid sealing on reassembly. Obviously when the block has not been decked there can be minor imperfections/pitting.

Anyone have any experience of it?

TIA

Boosted LS1

21,167 posts

259 months

Wednesday 26th July 2017
quotequote all
If you're using a composite gasket then it should conform a bit to grip the head and seal well. If you're using a MLS gasket then the surface finish of the block and head should be smooth enough to provide a tight seal. I can't see any point in using sprays etc. If the stock gasket is composite then you'll be fine.

Krikkit

26,500 posts

180 months

Wednesday 26th July 2017
quotequote all
Don't bother.

Get a pack of stanley knife blades and effectively "shave" the block surface (as if it were your face) to get rid of the old gasket without scratching. If you have time go over it with some very fine (>800) grit sandpaper to help key it, but don't add anything else. MLS gaskets will take care of everything for you once torqued up.

Leptons

Original Poster:

5,113 posts

175 months

Wednesday 26th July 2017
quotequote all
Thanks for the replies, looks like a no then! I was planning on using an OE gasket, seems to be made of some kind of composite with steel rings around the actual cylinders.

Boosted LS1

21,167 posts

259 months

Wednesday 26th July 2017
quotequote all
That will be perfect.

kev b

2,708 posts

165 months

Wednesday 26th July 2017
quotequote all
Is this one of the engines that has a problem with the threads in the block stripping if it has been overheated?

A mate had a 325 and the bolts pulled the threads out when tightened up.

Leptons

Original Poster:

5,113 posts

175 months

Thursday 27th July 2017
quotequote all
kev b said:
Is this one of the engines that has a problem with the threads in the block stripping if it has been overheated?

A mate had a 325 and the bolts pulled the threads out when tightened up.
Yes it's not got a great reputation! As far as I know it hasn't overheated though (it was pressurising the cooling system)so fingers crossed!

helix402

7,832 posts

181 months

Thursday 27th July 2017
quotequote all
Do not add anything to the gasket/block face. Make sure you clean all muck out of the bolt holes in the block, compressed air is best.

robinessex

11,046 posts

180 months

Thursday 27th July 2017
quotequote all
kev b said:
Is this one of the engines that has a problem with the threads in the block stripping if it has been overheated?

A mate had a 325 and the bolts pulled the threads out when tightened up.
An over heated engine won't make that happen. Unless the block was cherry red at some time!!

Leptons

Original Poster:

5,113 posts

175 months

Thursday 27th July 2017
quotequote all
robinessex said:
An over heated engine won't make that happen. Unless the block was cherry red at some time!!
It's pretty well documented. They're an alloy block and the bolts are Torqued to the equivalent of around 80NM.

helix402

7,832 posts

181 months

Thursday 27th July 2017
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Of the top of my head the tightening torque is 40Nm, 90 deg, 90 deg. It's been a while since I did one.

motorhole

658 posts

219 months

Thursday 27th July 2017
quotequote all
Yep, 40 Nm then two steps of 90 degrees is correct. Believe me, that second 90 degrees is pure stress bundled up into 14 discrete packages.

I managed it without pulling any threads. My advice would be as follows:

1) Make sure all threads in the block are impeccably clean. A clean head bolt should be able to be loosely wound into its hole by hand until it bottoms out (without the head in place). If it doesn't, threads aren't clean enough.

2) BMW specify using oiled bolts. Use regular engine oil. Too much oil is bad and can result in hydro lock in the threads. Use a drop of oil under the bolt heads and on both sides of the washers. A dribble of oil on the bolt threads. Then leave to drain on a sheet of card or paper.

3) Leave at least 20 minutes between torque stages to allow the bolt to stretch. I left it 30-40 minutes between each stage.

4) Hope for the best. Have wife/friend/pet to hand ready to console you if it goes tits up. If it goes to plan, you'll need a seat and a brew before you do anything else!

Edit: I also thoroughly cleaned all the new bolts and washers with carb cleaner and left to dry prior to oiling.

Leptons

Original Poster:

5,113 posts

175 months

Friday 28th July 2017
quotequote all
motorhole said:
Yep, 40 Nm then two steps of 90 degrees is correct. Believe me, that second 90 degrees is pure stress bundled up into 14 discrete packages.

I managed it without pulling any threads. My advice would be as follows:

1) Make sure all threads in the block are impeccably clean. A clean head bolt should be able to be loosely wound into its hole by hand until it bottoms out (without the head in place). If it doesn't, threads aren't clean enough.

2) BMW specify using oiled bolts. Use regular engine oil. Too much oil is bad and can result in hydro lock in the threads. Use a drop of oil under the bolt heads and on both sides of the washers. A dribble of oil on the bolt threads. Then leave to drain on a sheet of card or paper.

3) Leave at least 20 minutes between torque stages to allow the bolt to stretch. I left it 30-40 minutes between each stage.

4) Hope for the best. Have wife/friend/pet to hand ready to console you if it goes tits up. If it goes to plan, you'll need a seat and a brew before you do anything else!

Edit: I also thoroughly cleaned all the new bolts and washers with carb cleaner and left to dry prior to oiling.
Thanks for the wise words, sounds like dirty threads and losing track of which one you've torqued up are a big cause of stripping them. I had actually read a lower initial torque figure of 32nm. Also heard a few people leaving out the final 90DEG or using one figure of 50lbft!

paintman

7,669 posts

189 months

Friday 28th July 2017
quotequote all
Once you've done the initial torque put a thin line on each bolt head all pointing in the same direction - I used a paperclip & a tin of white paint I'd got knocking around when I did my RRC V8 recently. Trick I've used for years after being told it a long time ago!
Then when you do the angle tighten you can see which ones you've done & which ones you haven't.

ETA You don't need a fancy angle gauge to see when they've been turned 90 deg either!



Edited by paintman on Friday 28th July 14:13

robinessex

11,046 posts

180 months

Friday 28th July 2017
quotequote all
If you strip a thread, and insert can be used to fix it.

AW111

9,455 posts

132 months

Friday 28th July 2017
quotequote all
paintman said:
Once you've done the initial torque put a thin line on each bolt head all pointing in the same direction - I used a paperclip & a tin of white paint I'd got knocking around when I did my RRC V8 recently. Trick I've used for years after being told it a long time ago!
Then when you do the angle tighten you can see which ones you've done & which ones you haven't.

ETA You don't need a fancy angle gauge to see when they've been turned 90 deg either!



Edited by paintman on Friday 28th July 14:13
:nod:

Thats what the factory service manual advises for my engine.
I just put a dot of paint pen on each bolt head at the front after the initial 30 Nm torque up.
The second set of 90 deg takes a worrying (to me) amount of force, even with clean oiled bolts, but I've done it twice with no issues.

Leptons

Original Poster:

5,113 posts

175 months

Friday 28th July 2017
quotequote all
paintman said:
Once you've done the initial torque put a thin line on each bolt head all pointing in the same direction - I used a paperclip & a tin of white paint I'd got knocking around when I did my RRC V8 recently. Trick I've used for years after being told it a long time ago!
Then when you do the angle tighten you can see which ones you've done & which ones you haven't.

ETA You don't need a fancy angle gauge to see when they've been turned 90 deg either!



Edited by paintman on Friday 28th July 14:13
So simple but genius! Thanks