Hi All

I need to replace my X300 3.2 cylinder head due to valve seat recession caused by the LPG conversion. have bought a secondhand head from a specialist breaker and all of the clearances are in spec and everything looks in excellent shape.

I am after a bit of guidance here as the only manuals I can find are the .pdf versions and none I have found give a really detailed guide to replacing the head. The cam chain tensioner are different on my car too, the cap is one piece, whereas the manuals show on where you can release the tensioner through the centre.

The other grey area for me is the timing gear/chain arrangement. How do you feed it through the head? Take the gears off completely?

Any help would be most welcome

Cheers

Glen.

 

Glen,
There was an updated upper tensioner introduced, and it sounds as if that is what you have whereas your manual seems to refer to the old type. The updated tensioner has no manual adjustment capability, and has an arrow moulded into its top.
The chains should be able to be fed up through the space in the cylinder head with the cam sprockets in place, but be careful you get the cam timing right. The car will run, after a fashion, with the chain a couple of teeth out of its correct position ( ask me how I know this!) There is a simple tool for holding the cams in the correct position, and it's use is for all practical purposes mandatory.

 

Thanks mate. I have ordered the timing tool. Hopefully I will do the job next weekend. I'll let you know how I get on.


Glen.

 

Try my "noddy" guide to replacing the head gasket, should show you most things you need to do.

https://www.dropbox.com/s/tzkmagxdyd...0X300.pdf?dl=0

 

Brilliant stuff, just what the doctor ordered.


Cheer


Glen.

 

Hi All
Well, the good news is that I have changed the cylinder head and the compression on all cylinders is between 11.5 and 12.0 bar. Thanks for everyone's help.


The bad news is that the rough idle and "fluffy" running at higher speeds is still there, so it wasn't poor compression causing it after all. This is a tad annoying to say the least.


You can expect a few more posts while I get tot he bottom of it.


Glen.

 

Glen,
Sorry to hear it didn't fix your rough idling/ fluffy running problem, but your valve seat recession will be fixed, so it is worth having it ticked off the list.
You mentioned you had acquired the valve timing tool, so I take it that we can rule out the timing being out a tooth or two? From experience, it will run rough at idle and fluffy higher up if you get the timing slightly out. When I screwed it up, I wasn't using the tool to set the cam shafts as I figured they wouldn't move. I'm a little older and much wiser now!

 

Thanks. I treble checked the cam timing and am pretty sure it's correct. Holding it at a fast idle and disconnecting the coils on at a time point No1 as being the culprit, no difference when disconnecting the coil.


I swapped the coil with No2 and the fault stayed at No1, I then swapped the plugs and still No1. Took No1 plug out and it's sparking - that's as far as I've got.


Being dual fuel and the fault being the same on both LPG and petrol tends to suggest ignition, but both fuel systems get their injection signal from the same ECU so there could be a dodgy connection or broken wire deep inside the loom - what joy.


Next step is to plug my OBD11 reader in so see if that brings up any codes.


Keen for more advise as always.......


Glen.

 

Glen,
That narrows things down quite a bit. Have you checked the continuity of the low tension wires to no1 coil? If no power is getting to a good coil.....
Fingers crossed!

 

Hi yes.


Today an an ex Williams F1 auto electrician friend of mine checked every signal to every coil and fuel injector with an oscilloscope and everything is getting the correct signal. It's possible that No1 is not getting it's signal(s) at the correct time, but we can't think of anything that would cause that.


There is an air leak at the inlet manifold on No1 so I need to fix that before going any further, it could be confusing the MAF.


Glen.

 

Hi Glen,
Fixing the air leak at no1 would definitely be a good idea, and your mention of it caused me to track back to your previous post. When you said that the fault stayed at no1 even after you swapped the coils, you later said you would need to check your obd reader for any codes. Without having done that, how were you able to conclude that the fault stayed at no1?
Does your obd show any codes at the moment?

 

Hi, I concluded that the fault stayed with No1 by removing the LT wires to the coils in turn. When doing this to No1 there was no change to the running, but doing it to any of the others made the misfire worse.


The only OBD code that came up was 1621 which is a spurious immobiliser fault, not connected to my problem I think.

 

Glen,
What does the plug on number 1 cylinder look like? It would be worth pulling it for a look, and replacing it just to eliminate another simple and cheap possibility. If you pull it after the engine has been running, it would be interesting to see whether there are signs of unburnt fuel in the cylinder, failing which suspicion might start to move towards the injector....

 

All fixed - and very happy now.


It was indeed the air leak causing No1 not to fire. When I put the replacement head on, I forgot to clean the old gasket off the inlet manifold until after I had bolted the head down so access was limited to say the least.


I had missed a chunk of old gasket between No1 and 2 which was holding the manifold off along the bottom edge of No1 port. Removing this and applying RTV fixed the leak and the misfire.


Happy days.


Thanks for all the help along the way guys.


Glen.