4.6is low compression cylinder 2

[phill]

Not sure what to do at the moment with the car (answers on a postcard)

What happened :-

Driving back from Whitby on the A1M the car started to misfire and the EML started to flicker, came off the next junction and phoned the RAC. They changed the coil pack, no difference, changed spark plugs round, no difference, so was put on a flat bed truck and brought back to Manchester.

The day after took it to local indy garage, they checked spark and fuel delivery all ok. Checked compression and found it very low on cylinder 2 (think they said 45psi), they then added some oil down the spark plug hole and rechecked the compression the compression was considerably higher (think they said 160psi).

options are

scrap it
repair engine
find a replacement 4.6 engine (not easy)

Question - can you put a 4.4 in and attach it to the 4.6 gearbox?

phil

[weirdfish]

A lot would depend on what it owes you, what sort of mileage is on the engine, what condition the car is in generally etc etc as to whether you spend the money repairing it.
The problem is, once you start down the repair route you will always start to replace/ modify/ upgrade other components whilst the lump is in bits, just habit really.
If it doesn't owe you a lot and you're not that bothered about repairing it, you could always strip it down and sell the various parts, if you have the time of course, must be a few grands worth of bits in one of these beasts, even second hand.

[DougieV8]

What is diagnosis of fault? If a simple Gasket job then sort it! Have you had a repair quote?

If too expensive then 4.4 engines easier came by - i am sure it will be same ZF box, why would it be different!?

Come on - I am sure it deserves it!? all the best

[phill]

adding the oil to the combustion chamber; and the compression rising, points to the problem being with the piston rings or scoring of the cylinder bore.

[shadrack]

if your actually thinking of scrappin it give it a engine re build diy! if its the valves that wont be that expensive in relation to value of car, alternatively ill give you £750 for it far more than scrap price lol

[IanP]

[quote="phill"]
adding the oil to the combustion chamber; and the compression rising, points to the problem being with the piston rings or scoring of the cylinder bore.
[/quote]

+1 to that. I am fairly sure the bore is coated so no reboring. You can pick up second hand 4.6 engines but they are expensive (I know as I tried to find one). As for 4.4 engines, anything can be made to fit but realistically is the car worth it?

[rjkc600]

It sounds like a piston related issue to me.  Possibly cracked around ring lands or a worn ring.

A garage can do a cylinder leakage test, which will blast compressed air into the cylinder at TDC which will point out where the compression loss is, i.e. piston, exhaust valve, inlet valve.

Id personally repair the engine.  You can replace all piston rings, new gaskets and cam chain guides.  Get a quote from Phil at CPC for the work, he does rebuilds all day long on M cars, be prepared for a £3500 bill though unless you can DIY it.

[IanP]

My bill for a full engine overhaul (rings, bearings, chain, guides, and gasket set [how much for a head gasket???]) came to around £2500 without labour.  That was all genuine BMW bits, the Americans seem to be able to get pattern parts for these engines but I couldnt find any over here

[stevox5]

Hi Phil

As already mentioned I would get a cylinder leak test done next to try and verify if its piston/bore issue or valve related.
If the compression came back that well, has the garage tried restarting it with a new spatk plug just in case the bore was washed as a result of the missfire and not the cause? Worth looking a little closer at the quality of the spark and fuel delivery to that cylinder and restarting it once the oil has been applied to the bore as a first step I think.
If low compression is definatly confirmed as the problem I would get the head off that bank of cylinders to see if its valve train or piston related first as then you will have a guage of work involved and cost for repair.
If you like the car and the rest of it is in good order i think I would go for a repair rather than sell for spares.

Good luck whatever you decide.

[rjkc600]

For engine work only use genuine BMW parts.  Pattern gaskets do not last as well, especially on complex on high torque engines.  You do not want to do the job again in a couple of years.

[Raj]

I see an E39 M5 engine transplant being the route I'd take. Can you just imagine it.

[phill]

4.6is now sold, not sure what they are going to do with it, probably stuff it in an auction or strip it down into bits.

[Sanj]

Sorry to hear that Phill, know you liked that car... 

You sticking around buddy, or had enough of the X5 scene...

[phill]

Staying away from X5's, don't really need anything that big any more. Took the intravee out before I sold it so will sell that shortly with all the leads and KCA, as I am not going down the BMW route.

Phill

[Raj]

Oh well. Which marque you going for now then out of interest?