Diesel P38 rattly/smokey after head gasket swap

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sebw36912

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Hi all,

I have often visited this forum (google makes a habit of it too) but never had the opportunity to say anything until now. I'm in a bit of a pickle, I'm about to move house (next week!) and have had to replace the head gasket and skim the head on my 95 P38 with 200k miles after it started overheating consistently and pressurising coolant. I sent the head to be pressure tested and skimmed, it came back with good pressure but with hair-line cracks running between valves on 4 cylinders. Not having much time I have put it back on hoping it will at least see me a month until I'm settled.

I finished the reassembly today and bled the injectors and all seemed fine. Pinched them up and turned the key again and after a bit of hesitation and spluttering it fired up, but with a horrible metallic rattle and clatter. It is either coming from the head or timing cover by the sound of it, certainly from the top half. I followed the routine of filling oil up to full, running at 2500rpm for 5 seconds and then checking and topping up but the rattle and clatter remains and gets much louder as the revs increase.
There is also a constant stream of dark grey smoke out the exhaust.

I fitted the cam sprocket with cyl 1 in TDC with the dimple on the side of FIP sprocket visible as looking down from above. I have checked the upper chain tensioner since, it's tense although the rail seems to have travelled over further than I remember when I refitted it - the lever tool doesn't fit between rail and pin/bolt without having to first push rail toward slack position. The two cyl 1 cams were facing up/away from each other when refitting. I'm told the valves were removed for skimming.

Could it be to do with the chain or tappets? or something else?

All help right now would be very gratefully received.

Thanks,
Seb
 
sebw36912 said:
Hi all,

I have often visited this forum (google makes a habit of it too) but never had the opportunity to say anything until now. I'm in a bit of a pickle, I'm about to move house (next week!) and have had to replace the head gasket and skim the head on my 95 P38 with 200k miles after it started overheating consistently and pressurising coolant. I sent the head to be pressure tested and skimmed, it came back with good pressure but with hair-line cracks running between valves on 4 cylinders. Not having much time I have put it back on hoping it will at least see me a month until I'm settled.

I finished the reassembly today and bled the injectors and all seemed fine. Pinched them up and turned the key again and after a bit of hesitation and spluttering it fired up, but with a horrible metallic rattle and clatter. It is either coming from the head or timing cover by the sound of it, certainly from the top half. I followed the routine of filling oil up to full, running at 2500rpm for 5 seconds and then checking and topping up but the rattle and clatter remains and gets much louder as the revs increase.
There is also a constant stream of dark grey smoke out the exhaust.

I fitted the cam sprocket with cyl 1 in TDC with the dimple on the side of FIP sprocket visible as looking down from above. I have checked the upper chain tensioner since, it's tense although the rail seems to have travelled over further than I remember when I refitted it - the lever tool doesn't fit between rail and pin/bolt without having to first push rail toward slack position. The two cyl 1 cams were facing up/away from each other when refitting. I'm told the valves were removed for skimming.

Could it be to do with the chain or tappets? or something else?

All help right now would be very gratefully received.

Thanks,
Seb
Click to expand...

Did you have engine locked with locking pin at number one firing when you did cam timing? If the head has cracks it is scrap. Sounds like you did something wrong and the valves are hitting the pistons.
 
Yes I had the locking pin in the flywheel with cyl 1 in TDC. I've been going over it in my head but I can't understand how I could have got any timing wrong. I put a 4.6mm wedge between camshaft locking tool and intake side of head when fitting sprocket, #1 was definitely TDC. I wonder if the dimple on pump sprocket I was looking at was infact the wrong one? although if it's 180 degrees out I'd have thought it wouldn't run at all.
 
sebw36912 said:
Yes I had the locking pin in the flywheel with cyl 1 in TDC. I've been going over it in my head but I can't understand how I could have got any timing wrong. I put a 4.6mm wedge between camshaft locking tool and intake side of head when fitting sprocket, #1 was definitely TDC. I wonder if the dimple on pump sprocket I was looking at was infact the wrong one? although if it's 180 degrees out I'd have thought it wouldn't run at all.
Click to expand...

Don't know what you have done. But it is critical to be locked at TDC number one firing BEFORE the head is removed. Did you turn engine at all to clean piston crowns with head off? If you do it is important to turn the engine two revolutions before inserting timing pin. Or number one will be TDC exhaust stroke. Sounds like that is what you have.
 
I inserted the locking pin before disassembly but it turned out to be locked in BDC #1, didn't know there were any holes other than TDC on the flywheel. So I put it in TDC before reassembly, using the dimple on FIP sprocket as a marker for correct revolution, as mentioned in RAVE. I can't say if it was 2 turns or not, things weren't that straight forward.
 
I've just been looking up tappets and I have read that they should be filled with oil before fitting. I wonder if it's possible that they have become empty while the head was taken apart. What would the procedure be for filling them again?
 
sebw36912 said:
I've just been looking up tappets and I have read that they should be filled with oil before fitting. I wonder if it's possible that they have become empty while the head was taken apart. What would the procedure be for filling them again?
Click to expand...

Tappets on these engines expand when cam is removed, if you did not allow sufficient time for them to compress under cam pressure and the valves to sink back onto their seats before you started the engine you may have several bent valves. Even if the engine was timed properly. You should ALWAYS turn the engine at least two full revolutions by hand to check for fouls before attempting to start.
 
The head sat assembled for a week before fitting, so tappet contraction shouldn't be a problem. I did indeed turn the engine by the crank pulley two revolutions once assembled, nothing but wheezing and hissing with compression.

How quickly should tappets self prime?

I understand RAVE says not to reface the head. I replaced the head two years ago and followed that advice, I thought this time I would in case perhaps not doing so contributed to the leak this time around, and because it had overheated quite a lot. Is it known why they state not to reface?
 
It is most likely to do with the fact the piston crowns the valves run very close to each other to get optimum compression and efficiency....

If the head is skimmed this reduces the clearances and could have the potential to clatter valves.....on the Tdi engines, you have to measure the piston crown protrusion and select the correct thickness of gasket for that engine.

It may also be because of the thin-ness of some of the galleries and other such structures in the head, which could be weakened by skimming.

Need to Goooooooooooooooooooogle and see if there is any info on it.
 
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