Urgent cooling problem advice: E46 328i
Discussion
I hope PH's collective wisdom can help me deal with a cooling problem on my '99 E46 328i. I'm finding it hard to get my head around, and frankly using the car (a daily necessity) is scaring me s
tless at the moment.
Yesterday morning, the car warmed up pretty quickly, maybe in two miles rather than four, but I was getting no hot air through the heater vents. She then continued to heat up, uncontrollably and still getting hotter even at 50mph off throttle. This told me no coolant flow at all.. pulled over, and after a few minutes gently loosened the expansion tank cap to see if I could vent an airlock or whatever had happened. After that, on firing up and driving off, the temp gauge dropped below normal into cold, before rising back to normal where it stayed as I took it easy back home.
I thought I had maybe had some sort of airlock or blockage, and cleared it - that evening I tried "burping" the system by running the car from cold with the cap off, got it fully warmed, and it wouldn't overheat, but the heating was still intermittent. Thought I might be on the home straight.
Then this morning, I had exactly the same thing as yesterday. warmed up quick, no hot air in cabin, overheated, then after loosening the cap went back to cold->normal and became stable long enough to get home, with heating working again.
I thought the water pump might be at fault, but tonight I've just let the car idle from cold to warm, which took a normal time, and was getting no hot air in the cabin. Then, without me doing anything I heard a sort of click and the temp dropped to mid-cold, quickly recovered to normal, and I had hot air through the vents.
I now think sticky thermostat. Theory that when it's been hot soaked long enough, it opens and everything can flow normally. So I started driving to test it, and pretty quickly the vents seemed to lose heat but temp gauge was OK. On two occasions in a five-mile drive, the temp started to creep up, and both times I gave the car a lot of power in second gear to try and "force" things open. It worked both times and restored hot air each time. At times when the heater vents are working, the radiator bottom hose gets hot. When the vents are cold, so's the bottom hose.
On getting back everything seemed damn hot, and undoing the top bleed screw a few turns started letting a LOT of steam out.
What the hell is happening?! I hate cooling issues and I really can't not use the car at the moment, so this is pretty grim
Any help hugely appreciated. Thanks guys.
tless at the moment.Yesterday morning, the car warmed up pretty quickly, maybe in two miles rather than four, but I was getting no hot air through the heater vents. She then continued to heat up, uncontrollably and still getting hotter even at 50mph off throttle. This told me no coolant flow at all.. pulled over, and after a few minutes gently loosened the expansion tank cap to see if I could vent an airlock or whatever had happened. After that, on firing up and driving off, the temp gauge dropped below normal into cold, before rising back to normal where it stayed as I took it easy back home.
I thought I had maybe had some sort of airlock or blockage, and cleared it - that evening I tried "burping" the system by running the car from cold with the cap off, got it fully warmed, and it wouldn't overheat, but the heating was still intermittent. Thought I might be on the home straight.
Then this morning, I had exactly the same thing as yesterday. warmed up quick, no hot air in cabin, overheated, then after loosening the cap went back to cold->normal and became stable long enough to get home, with heating working again.
I thought the water pump might be at fault, but tonight I've just let the car idle from cold to warm, which took a normal time, and was getting no hot air in the cabin. Then, without me doing anything I heard a sort of click and the temp dropped to mid-cold, quickly recovered to normal, and I had hot air through the vents.
I now think sticky thermostat. Theory that when it's been hot soaked long enough, it opens and everything can flow normally. So I started driving to test it, and pretty quickly the vents seemed to lose heat but temp gauge was OK. On two occasions in a five-mile drive, the temp started to creep up, and both times I gave the car a lot of power in second gear to try and "force" things open. It worked both times and restored hot air each time. At times when the heater vents are working, the radiator bottom hose gets hot. When the vents are cold, so's the bottom hose.
On getting back everything seemed damn hot, and undoing the top bleed screw a few turns started letting a LOT of steam out.
What the hell is happening?! I hate cooling issues and I really can't not use the car at the moment, so this is pretty grim
Any help hugely appreciated. Thanks guys.
TheEnd said:
It could be a weak water pump that isn't circulating much, or maybe due to some sort of airlock caused by a faulty heater valve not allowing the system to properly bleed.
Is a 'weak' pump possible, and how could I best drive round it? The sudden steps between apparently working/not working really confuse me. And scare me about attempting any journey.Yes, it is particularly cold but there's a year-old 50-50 mix of good quality coolant in the car so it definitely shouldn't be a freezing issue - worth mentioning though!
First of all, stop cooking the thing. Your engine has an aluminium block and is sensitive to overheating- the head can crack and so can the block, or you can have plain 'ole head gasket failure. Basically don't risk it.
Regarding the problem, the obvious question is has the system recently been drained or disturbed, or is it leaking? If not then it can be any one of the faults you suggested- but if you don't know when these parts were last changed, you should order replacements for each and get stuck in. On a straight six BMW, it's just not worth risking it.
Regarding the problem, the obvious question is has the system recently been drained or disturbed, or is it leaking? If not then it can be any one of the faults you suggested- but if you don't know when these parts were last changed, you should order replacements for each and get stuck in. On a straight six BMW, it's just not worth risking it.
McSam said:
Is a 'weak' pump possible, and how could I best drive round it? The sudden steps between apparently working/not working really confuse me. And scare me about attempting any journey.
Yes, it is particularly cold but there's a year-old 50-50 mix of good quality coolant in the car so it definitely shouldn't be a freezing issue - worth mentioning though!
Drive round it!? FIX IT!Yes, it is particularly cold but there's a year-old 50-50 mix of good quality coolant in the car so it definitely shouldn't be a freezing issue - worth mentioning though!
It sounds like it might be a combination of issues - dodgy TSTAT and airlock in heater circuit. I know there being two issues at the same time is highly unlikely, but one issue alone can't cause the issues you're experiencing.
To try and remove the airlock in the heater circuit massage the heater hoses to dislodge the potential airlock.
To check the thermostat, check the radiator temperature after the car has 'overheated'. This should work if it's an outlet or inlet stat - if the rad is hot to the touch after overheating you should have no real issues with the Tstat. Then it could be some combination of airlocks causing the rest of the issues.
Question: have you had the car's cooling system serviced lately?
To try and remove the airlock in the heater circuit massage the heater hoses to dislodge the potential airlock.
To check the thermostat, check the radiator temperature after the car has 'overheated'. This should work if it's an outlet or inlet stat - if the rad is hot to the touch after overheating you should have no real issues with the Tstat. Then it could be some combination of airlocks causing the rest of the issues.
Question: have you had the car's cooling system serviced lately?
Russell, agree with all you're saying and if it starts to get hot, I'm keying off as immediately as possible and the gauge has never been to the three-quarter mark. Can't risk any of the failures you describe. The problem is that I can't fix it without driving it to get parts..
I have a replacement water pump, but doing the job will be tricky as I have limited tools here and my right wrist is in cast from an operation.. I'm tempted to get a thermostat too (£55, ouch) and do both.
The radiator does seem to get hot coolant through it sometimes (but not when overheating, only when working properly, equally I don't get hot air through the vents when she's overheating). This is what makes me think stat intermittently stuck closed, could that explain it all?
Having just tried to burp the system I didn't think there would be any airlocks left but there's been so much screwing around maybe some have reappeared. Sometimes some coolant loss is evident on the expansion tank, but looks like it's come from the cap as natural pressure release from excess temp.
As I say, coolant changed this year, and radiator and expansion tank are also quite fresh parts. The rest I don't know.
I have a replacement water pump, but doing the job will be tricky as I have limited tools here and my right wrist is in cast from an operation.. I'm tempted to get a thermostat too (£55, ouch) and do both.
The radiator does seem to get hot coolant through it sometimes (but not when overheating, only when working properly, equally I don't get hot air through the vents when she's overheating). This is what makes me think stat intermittently stuck closed, could that explain it all?
Having just tried to burp the system I didn't think there would be any airlocks left but there's been so much screwing around maybe some have reappeared. Sometimes some coolant loss is evident on the expansion tank, but looks like it's come from the cap as natural pressure release from excess temp.
As I say, coolant changed this year, and radiator and expansion tank are also quite fresh parts. The rest I don't know.
Yeah, I've seen how-tos regarding it, but most are starting from an empty system, and I was mostly observing to see if anything strange happened or if performance changed when the system wasn't sealed. Do you know of a good method to bleed without draining? I might drain it tomorrow if I can and if it looks like it might help.
I'd suggest parking the car on an uphill gradient, popping the upper radiator hose and filling through there until it overflows out of the radiator spigot, then jam the hose back on and top the coolant up at the header tank. Start it up, with the heater on naturally, and hold the engine at fast idle while loosening the bleed screw on the radiator, tightening it when liquid coolant starts coming out. Let it idle and check that the 'stat is opening by feeling the hoses.
Yes, check for leaks on the thermostat housing and expansion tank, if it's loosing water then air will be in the system and that's why your heaters blow hot/cold.
It can be hard to spot a small weep from the stat housing, it isualy leaks when hot and from the bottom, I used a small mirror so I could see under it.
Also the seam on the expansion bottle has a habit of splitting, this usually only leaks when it's warm and under pressure if it's a small split, check when warm.
It can be hard to spot a small weep from the stat housing, it isualy leaks when hot and from the bottom, I used a small mirror so I could see under it.
Also the seam on the expansion bottle has a habit of splitting, this usually only leaks when it's warm and under pressure if it's a small split, check when warm.
Change the water pump. The lack of heat from the heater with the engine being roasting hot indicates a lack of coolant flow.
You will probably find the impeller broken or spinning on it's shaft so be prepared to hunt for plastic that may have got into the engine. If you don't fish it out something else will break.
You will probably find the impeller broken or spinning on it's shaft so be prepared to hunt for plastic that may have got into the engine. If you don't fish it out something else will break.
Had very similar on a 1999 E46 323i (2.5). Couldn't make sense of it until removed water pump. Impeller had sheared clean from shaft. Various bits of the warm up/drive cycle, whilst fiddling with the heater, must have allowed enough circulation by convection alone. This was chum's car at 100K miles and 10 years on, with by looks of it original water pump.
Pull the pump off, or get a chum to do it bearing in mind your injury.
Best of luck.
Pull the pump off, or get a chum to do it bearing in mind your injury.
Best of luck.
FYI my 525i had similar symptoms and in fixing it I ended up replacing the radiator, thermostat, thermostat housing and expansion tank cap, the only reason the water pump wasn't changed at the same time was the fact that I removed and checked it and it was the stronger metal impeller type and looked recent.
Anyway, this is why I say order the lot and get stuck in. At 14 years and ***k miles old, most of these will be nearing knackredness.
Anyway, this is why I say order the lot and get stuck in. At 14 years and ***k miles old, most of these will be nearing knackredness.
Oh and steve BMW is bang on about the 'stat housing, mine was cracked at the bottom and was seeping coolant onto the front of the cylinder head where it immediately evaporated leaving little trace. I also learned not to use after market 'stats/housings because the BMW parts were much better quality.
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