E85 2.2 2003 – Strange Temp Gauge Behaviour and Engine Management Light

I’ve owned my Z4 (E85 2.2 2003) since September, and apart from the drive home when I bought it, I’ve barely done any trips longer than my 15-minute commute. The car is in great condition, with lots of paperwork showing it’s been well looked after, and just under 100k miles. I’ve noticed 'mayo' on the oil filler cap, which I understand is common with short journeys and cold weather. Obviously hoping it doesn't indicate a head gasket issue, but it wasn’t present until November when the temperature dropped.

Recently, I took it on a longer journey for once. About an hour in, the temp gauge suddenly cut out, with the needle resting at the lowest position, as if the ignition was off. I pulled over, checked under the bonnet (everything looked and smelled fine), and after restarting, the gauge worked again so I carried on.

However, later in the city, at low speeds, the temp gauge cut out again, and this time the yellow Engine Management Light (EML) and engine icon came on for all of 2 seconds, then went out.

After parking for an hour, the car drove fine for the return journey (80+ miles), with no further issues.

I check oil and coolant levels weekly, and today, the levels were unchanged. I also noticed almost no mayo under the filler cap, likely burnt off after the longer drive.

I’ve scanned the car with an OBD reader and INPA, but there are no errors that jumped out at me, just what I assume are old ones that may have been there for years related to minor things. I didn’t clear the codes, just in case.

Any thoughts on what might be causing the random gauge and light issues? Could the burning-off of the built-up mayo have caused these issues? Coming up to 100k miles, should I be looking to replace parts of the cooling system as preventative maintenance anyway? The odd thing is the car behaved perfectly fine throughout - it would have been easy to miss the brief warning lights and not notice anything was apparently amiss. I really would appreciate any advice or recommendations, thank you for reading!
 
The Mayo is down to your short commute, engine not getting hot enough or long enough on short runs. As to the gauge failing check the connection on the temp gauge for tightness and make sure its clean giving good connection. If it still cuts off then fit a new temp sensor, see if that cures it.
 
I used to get a bad mayo buildup up in winter from only driving the car 8 miles to work and back.

On a cold day on my commute i was barely getting the temperature needle into the middle which indicates a coolant temperature of 75 to 98 degrees Celsius, oil temp takes longer to get to temp than coolant.

Things I did that improved the mayo buildup were replace most the coolant system, thermostat made the engine get upto temp much quicker even on a cold day, and replacing the ccv system helped with the mayo as the system was completely gunked up with an oily sludge, even after all that if I drive the car short journeys I get some mayo.

If the car still has original, water pump, radiator, expansion tank, thermostat, ccv then I would look at replacing all of it and maybe all the hoses too.

Everything above on my car was the original parts and well overdue changing, a testament to how well built these engines are, still running on 20 year old parts and 100,000 plus miles
 
Thanks for your reply Joez4 :thumbsup:

Funnily enough I've just been scouring the forum about preventative maintenance now mine's about to hit 100k. I believe the cooling system is all original, apart from the expansion tank (previous owner replaced it after suffering the classic hairline crack).

I notice there are Cooling System Overhaul kits online but they only seem to be on US-based sites - but with this miserable weather I'm erring on the side of taking it to one of the specialists, with PMW and Power Developments both within an hour of me in Essex.
 
Autodoc is very good for parts but take awhile for delivery, there are good ebay sellers to such as car parts in motion. Real oem is great for finding part numbers with diagrams for the whole car, and there are lots of people on here who can help you.

A coolant overhaul is a straightforward DIY in my opinion, I have learnt alot working on these cars and think it is a good engine to learn on, if you do decide to do it yourself tho i warn you it gets addictive and you'll soon be replacing vanos seals.
 
Annoyingly inconclusive update on this:

I checked the temperature gauge connection for tightness, no play at all and trying to wiggle it didn't cause the gauge to cut out, as I had experienced. Then checked levels, cleared INPA error codes and took it for a 30mile run (first use of car since problem journey), mostly dual carriageway like when the problem first appeared... And absolutely no issues! Temp gauge swiftly got up to and then sat at halfway point throughout journey. Double-checked Engine Coolant Temp on my OBD unit and it just sat in high 90's as expected.

Checked INPA for errors codes when I got back, and one error has returned:

Variante: EWS3
1 Fehler im Fehlerspeicher
Fehlererfassung 1:
0x0023: WC-Toleranz erhoeht bei Schluessel Nummer 2 // translation: WC-Tolerance increased for Key Number 2
Fehlerauftreten: 1
statischer Fehler
Fehlercode: 23 21

As it's an EWS error it seems to be referring to an issue with a physical key (as opposed to key-value pair in the software?). Obviously a red herring as while I do have three keys I've only ever used the larger master key since owning the car and never had any problems.

So rather than continuing to use the car and just keeping an eye on it, I'm at a loss! Am I just being a fussy pr*ck who can't accept that these sort of random glitches are to be expected with a 20+ year old car? :rofl:

I'm now thinking it's possible I mistook seeing the temperature gauge as having briefly 'cut out' (literally a few seconds when on dual carriageway, pulling over became top priority!) when it may have actually just swung really far left, indicating a really cold temp and suggesting a momentarily stuck open thermostat, but I'm not sure a genuinely cold coolant temp is possible half hour into a motorway blast, and surely that would trigger an error code. Basically I'm clutching at straws!

I'll get some quotes for overhauling the cooling system for preventative maintenance's sake. I really like the idea of doing it myself, my only reservation is having the car in bits for days on end because I ordered the wrong part etc. If the weather were warmer, it would be less of an issue as I could take my time and use my motorbike in the meantime.
 
Sounds like the EWS needs to be realigned with the DME for that particular key, can be done with INPA and BMW Scanner 1.4 as well as higher end tablet scanners like Autel and Launch.
Google search found this https://www.bimmerfest.com/threads/ews-replacement-diy.1167689/
 
I get an intermittent ews error that allows the car to crank but not fire it always starts second time, but I go everywhere with a laptop and inpa just incase I need to resync the ews.

I just put it down to the battery either not fully charged or just the fact that as you said its a 20 year old car.

Did you Google the code you got?
Might be worth searching the e46 forums you will likely get way more threads on what the code actually means.
 
Thanks for your replies. :thumbsup:

I did google the code about the key and found out what I could, but as it's seemingly not causing any issues so far I'm going to leave it. I saw a post on another forum about a guy taking his INPA laptop with him everywhere in case his fix for this issue 'goes out of sync' and leaves him unable to start the car!
 
You could actually use a clever bit of software to stop the DME checking with the EWS on start up.
 
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