Overheating issue

B

Behr

Member
 Gloucester
Afternoon all,

2003 M54 2.5 -

I had anoverheating issue on the way home just now. The coolant light came on just as I'd pulled up at traffic lights. I immediately noticed a puff of steam from under the bonnet and very quickly drove on to a layby a few hundred yards ahead. Opening the bonnet I see there is moisture beading around the header cap and coolant clearly sat around in the undertray. I had no choice but to limp the two miles home gently. The odd thing is that the gauge never moved from the middle. I put the heater up to full and only had hot air intermittently so either the auto climate was regulating this (doubtful when on max?) or there was a circulation issue.

The belt is all fine as I renewed them (both) a week ago. The coolant level was also fine when I checked it on Saturday. Incidentally I read the codes (by coincidence) on Saturday and found an old P1622 'Map Cooling' code which I understand is thermostat failure. So I'm guessing water pump/thermostat at fault.

I'm resigned to cracking on and replacing the radiator expansion tank, cap and thermostat, and doing the water pump for good measure, but can't understand why I didn't see the gauge move. Any ideas/guidance on diagnosis welcome.

Incidentally, i was driving back from main dealer after a full KDS wheel alignment and air con service. The car hates me.

Saturday I spent all day cleaning the interior and got an airbag warning light for my reward. Probably from crawling all over the seats.

My car obviously isn't happy with all the attention it's getting!

Thanks,

Behr.
 
bad luck old chap! sounds like an intermittent issue i was having with mine on purchase.
replaced stat, pump, belts and coolant and the issue hasnt been back. my temp guage was reflecting the overheating tho.
post up results if you manage to get it sorted...
good luck :thumbsup:
 
https://www.bimmerforums.com/forum/showthread.php?753041-can-car-overheat-even-though-temp-gauge-display-stays-at-12-oclock-all-the-time
 
Chris_D said:
Behr said:
Oh pants. I posted in the wrong section. Mods - halp please!

Not a good day!
Click to expand...

U posted in the correct section. E85/6 problems....??
Click to expand...

I posted in the E89 section first, the mods kindly moved it.

The plot thickens. I went out just now to take the coolant cap off the now-cooled expansion tank and it lifted straight off in my hand. It was only placed back on. This must have been absent mindedness on my part at the weekend. I can't think the BMW mechanic would have taken it off whilst in there doing the A/C regas today.

Anyhoo, I added a litre of water to get it back to the normal Max level and ran the engine up but the heater is refusing to get hot and it's starting to move the temperature gauge up 10° past the 'normal' vertical half way mark so I shut it down. As I have just read; as the gauge isn't linear, this is very hot indeed. The top hose is getting hot so there is some circulation there. I think the thermostat has 'bought the farm' is is sticking closed or there is a pump issue - but I thought these had metal pump impellers? Regardless, I'm not taking any chances so have ordered an OEM pump, t'stat', expansion tank and cap.
 
if there is no heat, there is still air in the system. Before spending big bucks, after its cooled, check the level again. i bet its gone down. top up again, leave cap off and put revs up to about 2000 and hold it there. get someone to squeeze the hoses also.
switch off before it gets too warm and spills over. cap back on, run till warm, check heater output again.
Let it cool down and top up again if needed.
I think it just needs time to get the level right.
Worth a try before spending any money :D
Andy.
 
I do this every week to some car or other! Minis and Astras are awful to bleed up after coolant has been dropped out.
I use a vacuum fill tool on most cars now. Makes life soooo much easier!

Good luck.
Andy.
 
andyfanshawe said:
if there is no heat, there is still air in the system. Before spending big bucks, after its cooled, check the level again. i bet its gone down. top up again, leave cap off and put revs up to about 2000 and hold it there. get someone to squeeze the hoses also.
switch off before it gets too warm and spills over. cap back on, run till warm, check heater output again.
Let it cool down and top up again if needed.
I think it just needs time to get the level right.
Worth a try before spending any money :D
Andy.
Click to expand...

Thanks Andy

You were of course correct. It took another few litres of water this morning. I removed the slam panel trim to get to the bleed screw next to the filler neck, topped it up and ran it up hot. All seems fine, heater consistently hot and gauge just under normal zone which i figure is fine seeing as it's sat still and not under heavy load. I will replace the thermostat and expansion tank later this week anyway. I've also ordered myself a vacuum bleeder - thanks for your advice :)
 
No worries! Glad it's sorted.
It's the physics from school stuff.........leave cap loose, pressure stays at atmospheric, coolant gets to 100 degrees and boils over.
Cap on, pressure increases so boiling point also increases. Get to 100 degrees and .......No boiling!!
Like being back at skool eh? Lol!

Andy.
 
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