M54 gods were not kind to me today (head gasket, maybe?)

Z

Z4ZeeGermans

Member
So a quick background:

I've bought a 2003 2.5 back in June with 109k miles on the clock. It didn't really have a history record, but the MOT reports made it seem like she's been somewhat well taken care of. Not to mention I was not able to drive during the height of the pandemic between December 2020 and June (a long legal story for another time, maybe). Basically here was I, stuck without a valid drivers license for months until June, and it was friggin summer, and the pandemic seemed like it's finally waning away...

Long story short, I was like a drug addict in withdrawal, looking at Z4 ads until finally giving in to this beautiful 2.5... :D

Well, I thought I was ready for what's to come, I planned out all of the parts I was going to replace, and I was going to maintain it myself. It didn't have a history anyway... So I bought Bilstein shocks (the ones on the car were shot, unsurprisingly) new KYB springs, a bluetooth module to the original radio, Brembo discs all round, etc...

I knew I had to change the fluids soon too, but I chose to wait a little bit more on this until I move to a house with a garage. I wasn't driving it daily, and during the time I've been driving her, it was running flawlessly. Then later, while on a 200 mile road trip (give or take, I only added 700 miles so on the clock so far) she overheated. I tried to keep positive, as I knew the expansion tank is very likely to go bad, and eventually I replaced that too, along with the o-rings and brand new coolant etc.

Finally, today, just when I was thinking I sorted the overheating issue, all of a sudden she did her thing again; right when I was joining the motorway on a slip road. This time I knew I was screwed: When I checked, I actually could see the constant stream of small bubbles in the expansion tank. :headbang:

So I took a gamble on the car when I bought it. It seemed like I was alright for a couple of months, until I wasn't. Damn. Anybody know a reliable BMW specialist around Hull? :rofl:


PS: sorry for the long post, this happened during my house move, and it's been emotional. I don't want to let her go :)
 
Hi mate

Sad times

Did you change the water pump?

Are you sure you have boiled the head?
 
Well I actually was planning to overhaul the entire cooling system, but really I was waiting to move to a house with a garage. So I haven't done the water pump yet. I replaced all the brake discs, parking brake assembly, shocks and coils on both sides in the rear outdoors during summer, and it was brutal.

Anyway, I am positive I boiled the head because this happened right after I topped off the coolant. I don't really hear any weird noises from the pump anyway. I can only hope it's not horribly warped at this point. :?
 
It’s very rare for m54 engines to need a new head gasket, I’d get a sniffer test carried out to verify it’s necessary.
Rob
 
Z4ZeeGermans said:
I am positive I boiled the head because this happened right after I topped off the coolant. I don't really hear any weird noises from the pump anyway. I can only hope it's not horribly warped at this point. :?
Click to expand...

I'd take a minute to regroup and not jump straight to the worst conclusion.
Getting the sniff test done would be my first thought too.
If the pump is not turning then you will get localised boiling which could well be the bubbles you're seeing. Remember that with the cap off there is no pressure held in the system so it will boil more easily.
Then there's the possibility the thermostat is stuck closed so nothing is going through the radiator.
In short, I think there's a lot to consider before you get too woeful with it.

PS. Have done all the suspension and brakes on a 2.2 and a 2.5 now, on a gravel drive, messing around with ramps and axle stands on paving slabs. I book Saturdays for cars and Sundays for traction! Fun isn't it?
 
Hey thanks for the encouragement guys. Now that I think about it in a calm mood and a clear head, yeah you're right; it might be the head gasket, but it may as well be a bunch of other things too. I know for a fact that the radiator is original, and I'm willing to bet the water pump and fan clutch also is the same.

First time it overheated the alternator got cooked off, so I replaced that (I replaced only the voltage regulator on it before). So there is a possibility some other components finally gave out.

I did order a sniff tester, I'll have it by wednesday. I reeeally really hope it's not the head... Cheers for the support :driving:
 
I've never heard of an alternator being damaged by overheating - i think there is something else going wrong here.
 
Well, after it's first overheat situation (before I replaced the exp. tank) I was on a roadtrip and I noticed the windows needed a reset and the radio went back to factory settings. I have a new battery already, so I figured there was something wrong with the alternator. I had the odd bulb warning on the dash before I replaced the voltage regulator anyway, so the alternator was obviously being overworked until I got my hands on it.

Actually, after I took out the old alternator, I saw that when I tried to spin it, it was locking up intermittently. So that's how I know :)

I guess the bearings inside got gunked up and seized due to hot coolant spray and high heat after all these years. It's not surprising to be fair.
 
Well, finally I've got some update on this. I've tested it with a sniff tester, and it spewed out almost all the test fluid, however there was a very little amount remaining in the test thingy and bubbles going through it did not make it change colour one bit. So, I refilled it and had a second go at it, this time there wasn't even any bubble up for 5 minutes or so.

The only problem I have here is that the temp started creeping up rather quickly due to all the fluid it lost the last time. This meant I could not test it out for say, 30 minutes to be 100% sure... But at first glance it looks like its something else in the cooling system, which is something I've been planning to overhaul since I bought the car anyway.

I will do the test once again when I fill the system up. (That will be a while though)

Happy days :driving:
 
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