BMW 540i compression readings from AA

[mons2b 0]

Hello anyone else taken their BMW e39 into the AA for a full test and had the compression readings back? I had a 1997 E39 Japan issue 540i and about three of the cylinders were at 80%. Three others were at about 100% and the last two were in the 90%+ range. About 147,000 on the clock. (Report said satisfactory for age and mileage).

What are other peoples AA readings on their BMW V8's?

Edited February 6, 2007 by J B W

[jochen 4]

Hello anyone else taken their BMW e39 into the AA for a full test and had the compression readings back? I had a 1997 E39 Japan issue 540i and about three of the cylinders were at 80%. Three others were at about 100% and the last two were in the 90%+ range. About 147,000 on the clock. (Report said satisfactory for age and mileage).

What are other peoples AA readings on their BMW V8's?

Never bothered on my '97 540i, I only had 78,000 kms when I bought it, figured it was gonna be OK.

If you're gonna give the car a once-over I'd suggest you clean the ICV valve, mine was full of carbon, gummed and sticky. Now it's clean and swings open and closed freely, and I idle better.

ICV is dead easy to access on the M62 V8

PS: If you want your TV/Radio/nav etc working - talk to me. I can help heaps.

[mons2b 0]

Never bothered on my '97 540i, I only had 78,000 kms when I bought it, figured it was gonna be OK.

If you're gonna give the car a once-over I'd suggest you clean the ICV valve, mine was full of carbon, gummed and sticky. Now it's clean and swings open and closed freely, and I idle better.

ICV is dead easy to access on the M62 V8

PS: If you want your TV/Radio/nav etc working - talk to me. I can help heaps.

Would the ICV have any affect on compression? If the cylinder head was one of those dodgy nikesal (cant spell it) would the compression be even lower?

JW

PS any link to ICV cleaning instructions?

[hotwire 352]

Hello anyone else taken their BMW e39 into the AA for a full test and had the compression readings back? I had a 1997 E39 Japan issue 540i and about three of the cylinders were at 80%. Three others were at about 100% and the last two were in the 90%+ range. About 147,000 on the clock. (Report said satisfactory for age and mileage).

What are other peoples AA readings on their BMW V8's?

Firstly, idle control valve (ICV) has no bearing on compressions - just controls/maintains stable idle under all situations. I would expect more even compressions than that for that milage BUT depends on its origin/ service history. Asian cars - particually Jap are reknown for lack of servicing which can dramatically shorten an engines lifespan. Could at best, be gummed up & just need a good flush / service to resurect compressions or at worst be the start of something more serious.

[RvT 9]

Ditto on "PS any link to ICV cleaning instructions?"

My e39 has quietly developed a sudden surge when you are slowing down and almost stopped. Almost like you accidently acelerated at 2km/hr but your foot is on the brake. Doesn't happen with the air cond on. Is this related to the ICV valve?

[Eagle 1662]

my e34 used to surge sometimes when starting off in D or R, cleaned to ICV and the problem went again. Easy enough do do, get some throttle body\carb cleaner and you away

[kiwi535 538]

nikasil bores not cylinder head....Nikasil was an issue for some E34,s (NOT NZ ones)by the time the e39 came along they had switched to Alusil.I dont know if the nikasil "problem" occured in japan.These are relatively high compression engines,if the rings are gummed up a bit that could affect compression.A couple of squirts of oil will seal it up for a compression check.A bmw dealer will give you a much better check (for a BMW) than the AA.

[kerrynzl 3]

A couple of squirts of oil down the plug holes ,then compression check it again [oil acts as a temporary ring seal] If it regains compression then the rings weren't sealing or worn. If the readings stay the same it's usually valves that are leaking [Oil down the plug holes leaves the valves dry]

[mons2b 0]

nikasil bores not cylinder head....Nikasil was an issue for some E34,s (NOT NZ ones)by the time the e39 came along they had switched to Alusil.I dont know if the nikasil "problem" occured in japan.These are relatively high compression engines,if the rings are gummed up a bit that could affect compression.A couple of squirts of oil will seal it up for a compression check.A bmw dealer will give you a much better check (for a BMW) than the AA.

Thanks for advice. I would have thought that given the muturity of the car if it had the factory head issue it would have been dealt with by now. Was only imported to New Zealand in 2003. Having done around 70 thousand at that stage.

Engine seems to run well and smooth so I dont know.

Nothing I can do but keep my fingers crossed and keep my expensive warranty close by..

JW

[jochen 4]

Ditto on "PS any link to ICV cleaning instructions?"

My e39 has quietly developed a sudden surge when you are slowing down and almost stopped. Almost like you accidently acelerated at 2km/hr but your foot is on the brake. Doesn't happen with the air cond on. Is this related to the ICV valve?

This will be a dirty, sticky ICV for sure.

Dead easy to clean, can be done in an hour:

(for a V8)

1. Remove top black cover (press the 4 x buttons (item #2 in pic below) in till they click, lift off)

http://www.realoem.com/bmw/showparts.do?mo...hg=11&fg=55

2. Locate ICV right at front of engine, (item #23 in pic below) it is just beside the scondary throttle housing tube (item #6) at the front of the engine:

http://www.realoem.com/bmw/showparts.do?mo...hg=13&fg=15

3. Remove hoses, slide out of rubber holder. remove from car

4. Check inside flap valve - should swing freely. Bet it doesn't because it will be covered in black stuff

5. Spray insides with carb cleaner till clean. Valve should swing freely. Wipe with clean cloth. Don't scratch anything inside the ICV!

6. Re-assemble.

[kiwipetrolhead 1]

Hello anyone else taken their BMW e39 into the AA for a full test and had the compression readings back? I had a 1997 E39 Japan issue 540i and about three of the cylinders were at 80%. Three others were at about 100% and the last two were in the 90%+ range. About 147,000 on the clock. (Report said satisfactory for age and mileage).

What are other peoples AA readings on their BMW V8's?

I have never had a compression test done on my '94 540i and I don't have any urge to do so - the spark plugs tell me enough about the engine's condition. It's done about 240,000K and it doesn't use any oil and it runs sweet.

But it's very common to have some variation in any car without there being any fault. With more cylinders, of course the odds are greater for variation too. If you want to test things further though, squirt some engine oil down the spark plug holes (not too much, about 3 or 4 squirts from an oil can is about right), spin engine over for a few seconds then do another compression test. If the compressions move up, then it's a sign of leakage past the rings. If the compression remains the same, burnt out (or burning out - leaking) valves are the issue. Another trick is to put new plugs in and some good upper cylinder lube in the tank and take the car for a good hot thrash (yip, somewhere where you won't get caught, and being a 540, you have to go pretty damned fast to thrash it enough) then do another test. (Holding it in third gear at 5,000revs to the redline for a few seconds each time is good.) If everything is OK then you'll find the compressions are a lot more equalised after that. The alternative to a good thrash is a nice long hot trip, but even then it might require raising the revs up to around 6,000 in third gear a few times to clean out any determined carbon deposits and/or loosen the sticky rings properly.

Well, that's what I used to do to cars in my mechanic days. This method worked really well on cars owned by little old Nanas (not always a female :-) that puttered around town all the time. Sometimes I'd get massive amounts of smoke out the rear end as I got the revs up, but after a few high-rev blasts in third gear, the car went well again. So it often really didn't need the 'traditional' tune up that it was booked in for - what had the most impact on the 'tune' of these cars was the good thrashing I gave them. Sometimes I also gave the engine a good treatment of Redex (upper cylinder lube) as well (a bit in the tank, but also some down the intake while the engine was running off the idle, and was hot - lots of sweet-smelling smoke everywhere... fun!)...and that often performed miracles. My boss often used to try the car out after I completed the tune up and more than just once or twice he said to me, "That's the best that car has ever gone!"

Of course, with modern engines warming up lots quicker and with better petrol (cleaner burning) and leaner running engines, bad carbon deposits and sticky rings are pretty much a thing of the past nowadays. But there can still be some issues, especially with big engines doing slow round-town running all the time.

P

[kiwipetrolhead 1]

Firstly, idle control valve (ICV) has no bearing on compressions - just controls/maintains stable idle under all situations. I would expect more even compressions than that for that milage BUT depends on its origin/ service history. Asian cars - particually Jap are reknown for lack of servicing which can dramatically shorten an engines lifespan. Could at best, be gummed up & just need a good flush / service to resurect compressions or at worst be the start of something more serious.

I spoke to a guy in a tyre shop last week who has a Jap import 318. He said he only buys used Jap imported cars because they are better serviced than NZ-new cars. I said nothing to that one, but I was surprised to hear someone say such a thing - especially when he works in the motor trade and has mates working in garages. In my own experience they are not serviced well at all - they are treated as discard-able items by the Japs... so why bother servicing them! (Fair enough.) So I agree with your comment there 'hotwire'. Personally, I'd never buy any used import.

I also agree that lack of regular servicing can have an impact on compressions, for sure. Dirty oil will leave deposits around the rings and make them stick in the grooves in time. I've seen some supposedly low-mileage (yeah right) used imports with very grubby engine internals. In addition to my last post in this thread, a good flush and then new, good quality oil in the engine will also help equalise compressions if that is what the cause of the problem is (in addition to some upper cylinder lube treatment and a good thrash). If it's a used Jap, then most likely that is the problem too!

P