E86 lost compression on cylinder 3. Advice required.

[Bmwz4ruby]

I’m hoping for plenty of replies on this one so I can make the right call.

Background: Whilst driving on a dual carriageway at a rock steady 77 (indicated) mph (which I had been doing for at least 40 miles my 2006 E86 dropped a cylinder whilst going up a gentle incline followed by another at the top of the hill. I stopped at the services and managed to regain a cylinder by messing with the coil packs.

The following day I ordered a full set of Bosch coil packs (they weren’t expensive so thought it worth doing anyway as the fitted ones were original 2006 items which had done 125,000 miles).
This didn’t fix the problem.

Fast forward to now and I have done a comp test. All cylinders fine apart from cylinder 3, maybe 2 bar only. Fault codes also saying cylinder 3. I have also put some oil in cylinder 3 and redone compression, no change.

I will add at this point that I have already decided I need an S54 powered Roadster so this car is definitely being sold.
I will also add that i have obviously come to some conclusions about the problem and the fixes. I’m not going to offer them here as want to hear others thoughts.

So what to do?
Sell as is, complete and running but only on 5 cylinders.
Fix and sell (how much to fix will affect my decision based on my purchase price of the car versus the effort/cost to do it). I will do most of the work myself.

Final bit for now, car spec:
Ruby black manual SI sport coupe owned for nearly 3 years
125,000 miles reasonable condition
Fully complete with loads of options (rear PDC, cruise, Bluetooth, auto lights/wipers, cup holders)
Sports heated red leather seats
Stainless cat back exhaust fitted (original still retained to go with the car as well)

Let me know your thoughts on issue and cost to resolve.
How much car worth as is (poorly) and also fixed.

I want to resolve it one way or the other quite quickly in order to get a Z4m roadster.

 

[Jon2215]

Have you removed rocker cover and checked the valves on cylinder 3 are opening/closing?

 

[Bmwz4ruby]

Have you removed rocker cover and checked the valves on cylinder 3 are opening/closing?

I have had the rocker cover off but not turned it over by hand (yet). It all looks fine in there (of what you can see anyway).

 

[Street]

I'm fascinated by this so will follow your progress. I wonder if wiggling the coilpack was a red hearing on the other cylinder. Could a couple of cylinders have burnt or carbon clogged exhaust valves and number three got bent or misseated perhaps? Any other symptoms? Were the plugs clean, any head gasket related symptoms elsewhere? Either way I guess valves or gasket and the heads coming off to investigate and fix.

The market is really slow at the moment so you have a time / value exchange on your hands even with a healthy car. Comparing to AT it looks like a healthy 125k miler list around the £6k mark. With a broken engine I think you'd lose a grand to sell as is to offset repair costs by an indy. Your market would be limited to people willing to do it themselves and take a risk there aren't other consequential problems.

 

[Bmwz4ruby]

Great reply Street.

My thinking is very much the same as yours. A bent valve(s) on the exhaust of number 3. Plug was not clean like a perfect running engine. There are zero head gasket issues, water/oil or vice versa, no overheating etc.

Both options are viable to me but I am slightly more inclined to whip the head off myself. If I took it off and found a valve not seating properly, then is it sensible to reseat them all and refit the head with a new head gasket? Would it be wise to get it skimmed?
Just trying to work out the cost. Also I think I need a bracing tool to undo the cam sprockets, I don’t think this is a cheap item.

 

[Street]

Why not try both? Pitch it for sale as is and see if you get any interest. Meanwhile plan your attack to fix.

A timing alignment kit can be had for about £70. There’s a mixed opinion on skimming if it hasn’t overheated. A local price and lead time might sway you one way or the other.

I’ve just got the moon miler coupe road ready. I’m looking forward to doing a compression test to see what shape it’s in.

 

[raymond.harper]

A second-hand engine could be fitted but you would need a hoist and quite a few hours doing the work. Repairing the cylinder head could be an option but the rings may be at fault and again very time-consuming. I would sell the car as it is for around £1500, it is probably worth that in parts for someone with the space to break the car. Even if you got the car running, car prices are all over the place.

 

[deltasierra]

Until you take the head off you won’t know, if it’s a valve that can be fixed economically, piston, rings and bore it gets difficult, finding a good replacement engine is not going to be easy or cheap, my guess is someone with the skills will rebuild it.

 

[Mike6]

Can you get a boroscope in there and then turn engine by hand. That might show if you have a bent valve. You mention oil poured in the bore but compression not increased. To me that would indicate a head problem like valve seals or burnt valve head.

 

[Mike6]

Can you get a boroscope in there and then turn engine by hand. That might show if you have a bent valve. You mention oil poured in the bore but compression not increased. To me that would indicate a head problem like valve seals or burnt valve head.

 

[deltasierra]

Second thoughts before you take the head off, the N52 has a complicated valve system make sure there is nothing broken or worn with the “Valvetronic” system (google it) a fault there could easily hold a valve open or not operate it at all

 

[Smartbear]

Until you take the head off you won’t know, if it’s a valve that can be fixed economically, piston, rings and bore it gets difficult, finding a good replacement engine is not going to be easy or cheap, my guess is someone with the skills will rebuild it.

He could get a leak down test carried out to find where the compression is leaking without any disassembly
Rob

 

[Bmwz4ruby]

Second thoughts before you take the head off, the N52 has a complicated valve system make sure there is nothing broken or worn with the “Valvetronic” system (google it) a fault there could easily hold a valve open or not operate it at all

That’s an interesting point. I will read the fault codes again and see what comes back. Failing them giving me any pointers am I going to be able to see (visually) a fault?

Also, I have the skills, time and interest to do the job myself, I also already have valve spring compressors from my Mk2 Golf days.

 

[deltasierra]

This is a pretty good explanation of the way to all works and the problems

https://bimmerprofs.com/valvetronic/

 

[Shadbolt83]

Just playing catch up on this and interested as to how you got on? Any update on diagnoses or decision yet?