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Mystery problem found after 2,5 years. E-box fan impacts performance!

11K views 26 replies 15 participants last post by  1stoutm5 
#1 ·
Hi Guys,

In my post of January 2016 I described a mysterious lack of power:

http://http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/497842-mysterious-lack-sharpeness-my-m5-help-needed.html

I have spent enough money on my M5 to cause a devorce in the mean time:)

- New Maf's
- New Lambda's
- New fuel pump
- New fuel filter
- New vacuum release valve
- New Cat's

After advice from you guys on this forum:

- New CPS's
- Full Vanos revision
- Full check on fuel supply

Then my engine started to make a knocking noise when leaving the highway. It was in the shop for a month already after having replaced the rod-bearings (not the cause of the knocking sound). We were unable to find the source of the knocking sound (spent some hours reading on this forum). Then decided to have:

- A complete engine overhaul.

After three months of rebuild finally engine got reinstalled in the car. Then things got worse: timing chain missed out at the first start and valves hit the pistons: so much for my rebuild engine: it was buyond repair.

Fortunately the guys at the shop were fully insured so I had I completely new s62 installed (l love BMW: you can just order a new engine). Just finshed the first 2.000 km last week. But....the lack of power was still there.

I had the e-box fan error for some time already but did not believe it could impact performance. But to get rid of the fault code I ordered a new one 1,5 year ago together with the vacuum release valve. But there is this mistake in BMW's coding: I got the wrong E-box fan (it was having the two wire version instead of the three wire or vice versa). When the correct one was delivered I left it at the shop and due to lack of time, the believe that temperatures in the Netherland could not cause any issues, and having switched to a new BMW specialist I left it a the old shop.

I had it replaced last week though: and there it is: best car in the world is back. Torque is back, responsiveness is back, driving pleasure is back. After 2,5 years of puzzling the mystery is solved. It was the E-box fan. I have read most of the threads on the forum this week about the E-box fan and did not found a single indication that this 130 euro part could impact performance to this large extent besides hot start issues.

So for all you guys: before you start spending the amount of money I did: if you have the 8F Ebox fan code: replace it! BTW: I still could not find why the E-box fan impacted power/torque so much.

Cheers!


Joost
 
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#5 ·
Unreal unbelievable story and thanks for sharing. I had an issue drove me nuts for a year and it turns out a cracked fuel regulator vacuum hose. But you went thru full Rebuild then engine replacement wow. And your marriage still holding up :). That's a wild story and congratulations for your brand new s62 :D
 
#11 ·
Most likely because you didn't hit the combination of weather and driving conditions whilst your e-box fan was FUBAR.

I've had this issue on both of my E39 M5s...

Both very similar conditions and also performance issues...

Typically the outside air temp in excess of 25c and driving conditions tended to be slow / congested traffic.

When those both combine I found that the car was a bag of nails when you came to floor it, almost like a limp mode had kicked, it would struggle to hit 4k revs and 70mph was a distant pipe dream.

If you allowed the car to cool down over several hours the symptoms would disappear and normal service was resumed, so taking it to a garage invariably meant there was no symptom for them to see, only the e-box fan fault code which could have been there for months without any performance detriment.

I'm sorry I didn't see the OPs original post as I may have been able to share my experience from some 8 years back...

For what it's worth IIRC the 530i shares the same ebox fan as I sourced a 2nd hand one for my last car for literally pennies, it's a simply DIY job although getting the nuts off the box that the e-fan sits in can be a pig as the plastic degrades and the nuts and bolts can just spin.
 
#8 ·
There are several ways the E box fan can fail. It is two speed and if you lose low speed that will effect you. If you only lose high then you will not notice, that is the most common failure. If you have it seize that will effect you and there are two possible things that can cause the bad running.

I am not going to debate this I have in the past, and am content that the DME temp sensor is the primary air temp reader so if the fan is not blowing on the sender the car thinks the outside temp is different. It has been confirmed that is exactly how the similar M3 dme works. So no low speed, no air, wrong temp.
If the fan seizes and I think it was M5Demon that first noticed the rather large fuse on the circuit and noticed that the CPS and other things are on the same feed as the fan. So a shorted fan will likely cause strange things in all of those circuits.
 
#22 · (Edited)
Sorry if I'm opening a can of worms but are you saying the ambient air temp and the DME temp cross talk to one another?
I'm having the same issue as the OP, changed all the "power robbing" maint. Items here lately but still doesn't feel up to full power. My ambient temp sensor on the fender liner was broken off after hitting a raccoon around 60mph as well as having the E-box fan code.... could these be part of my loss of power issue?


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#10 ·
Wow. IIRC there were like 3, zero mile s62's still in bmws possession. I believe they were listed for $29,999.

Whats the shop name? Sounds like I need to get a rebuild there. lol.


If that's a brand new motor, than you lucked out BIG LEAGUE.
 
#14 · (Edited)
There's apparently plenty of supply -- at least there was the last time I had my parts guy check availability for 11001407803. BMWNA's MSRP is $23,854.35, but from the right source you can buy one for a bit less than $18k.
 
#12 ·
My Ebox fan was not operating in ambient temps of above 30 deg C. I was in heavy traffic for over an hour and recall seeing the 'ATMP' in the secret menu hit above the high threshold reading and not come down to ambient until some time later with airflow from cruising at 60+ mph.

Yes the car was sluggish but the car is also sluggish in these conditions with a working ebox fan. There are other factors to consider also i.e the sucked air temperature for the engine and its direct affect on ignition timing. within the dme programming. I have proved this on the dyno with both of the e39 M5's i had.

These cars don't make their quoted outputs in all environmental conditions.
 
#15 · (Edited)
Is your 99 not the original setup, with a three wire fan? Produced with rectangular mirrors? I know the way the ebox worked and how it functions was introduced in the M5/3 but I thought it started at production which was model year 2000. Model year 99 was pre production?
The date of the switch was 09/99 which would be MY2000 and up all my99 and earlier are a different setup and work totally different.
It was still a three wire fan though. The two wire fan is my 2000 and up. The Op also has a pre production car so now I am wondering but maybe his was seized causing slow or confused CPS response which sound like his symptoms.
 
#20 ·
Hi Guys,

Thanks for all the feedback. The problem with the wrong wiring was as follows: production date of my M5 is april 1999. Apparently they changed the wiring as of production 9/99. But if you order the E-box fan based upon your VIN I got the one with the new wiring. So there is a mistake somewhere in the BMW sytem. The wrong one for me had black plug and the right one a white plug with three wires.

New engine was around 17.400 euro including VAT ex labour.....I only paid for the engine rebuild which was close to 11k (including VAT). But already the prior Vanos revision was close to 3k. But in finance we call this "Sunk-Cost":). Just had it revaluated for insurance but still await the outcome of the new engine on the value of my car.

Problems I had did indeed feel as engine was short of fuel. With the old engine I did a dyno run and ended up with 440 bhp (I run evolve Alpha-N, 4-1 headers and carbon cold air intakes). But it was low on torque: only 470nm while my E39 540i was doing 438nm (and 311 BHP instead of the standard 286:)).

Just fisnished the first 2.000km and went WOT for the first time last week: performance is getting scary again. Puls like a freight train!

Cheers!
 
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#26 · (Edited)
Not sure I have found baro in the diagrams but never found the sensor. I also have never found the inlet for the Ebox fan, short of taking the dash and everything off the inside firewall I may not find it. I suspect it goes to the front of the windscreen. In 2001 a sun sensor was added to the same spot.
 
#27 ·
Bumping an old thread just for future info... this past weekend I finally got around to reinstalling my ambient temp sensor down by the passenger fender liner. Wow is all I have to say, car feels much different, exhaust note is crisp and even my MPG's have gotten better. This clarifies that the ambient temp sensor crosstalks with the DME for possibly air/fuel mixture based on outside temps.


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