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Car overheating, losing water - but we can't see where from!


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#1 coolcity

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Posted 12 July 2011 - 06:35 PM

Um....where to start! I'll give as much info as possible so here goes...

4-3 weeks weeks ago when doing a general oil check etc. I checked the water level, strangely something I don't normally do - but it was low and took over a litre of water. No other problems since then until last week when the "low water" warning light came on. Sure enough it was low again and took about a litre. Since then I have had to keep topping it up each day and would normally just take it into the main dealer (or at least a "proper" garage) but then a friend of a friend who knew a very good mechanic etc. etc. said he would sort it out for me. I was a bit surprised when it came back with a new radiator and £160 bill as I thought it might have been just a leaky pipe or something, but I'm not mechanically minded so...

Thing is, it's now even worse. I can top it up and it will run fine for a few miles but then still need up to 2 litres of water when I stop - or it can run 30-40 miles and take 2 litres of water. Other times I can fill it up, yet the low water light comes on straight away. I just did this, then drove to miles to the mechanic's place (with the low water light on all the time) and though the temp gauge had not moved it was clearly starting to boil when we opened the bonnet, and took at least another two litres of water. But there doesn't seem to be any significant leak anywhere, just the odd drip. To me, it doesn't make any sense.

He didn't understand it either, the only thing he said is the pipe at the bottom of the rad seemed to take an awful long time to get warm, but we had it idling for 30 minutes with no significant change in water temperature, and nothing leaking.

What is happening here?

Car is an E46 318i, 53 plate, 65k miles.


#2 Wash

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Posted 12 July 2011 - 06:50 PM

You should stop driving your car completely until the leak is fixed, you risk overheating your car and blowing the head gasket.

Have you taken off the air intake cover thing? The one with the BMW badge on it?

I've got the same engine as yours I think (N42B20). I've got a coolant leaking coming from the left side of the engine, right at the bottom.
Here's a video I made a while ago showing the leak:



#3 coolcity

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Posted 12 July 2011 - 07:12 PM

You should stop driving your car completely until the leak is fixed, you risk overheating your car and blowing the head gasket.

Have you taken off the air intake cover thing? The one with the BMW badge on it?

I've got the same engine as yours I think (N42B20). I've got a coolant leaking coming from the left side of the engine, right at the bottom.
Here's a video I made a while ago showing the leak:



That's the problem - we can't find any leak! We don't know where the water is going! We have had that top cover off and the bottom floor pan too.

My best guess - and it is a guess - is that it is blowing water out of the expansion tank when it overheats (i.e. boiling over) when I'm on the move, then when I stop there is no water dripping because there isn't enough left in it to reach the overflow, if you see what I mean. It's the only way I can explain why it is losing water but can't find a leak. The question is why is it doing this?

I'm a bit pi$$ed off to be honest because I don't think it ever needed a new rad, but you hope that the guy doing the job knows a bit more than you do and what I know about engines you could write on the back of a postage stamp.

#4 Wash

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Posted 12 July 2011 - 07:14 PM

Have you tried running the engine for a while and putting some cardboard underneath with the undertray/floor pan removed?

#5 coolcity

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Posted 12 July 2011 - 07:35 PM

Have you tried running the engine for a while and putting some cardboard underneath with the undertray/floor pan removed?


As per the original post we had it running for around 30 minutes with nothing leaking, floor pan was off so we would have seen any water drip onto the floor. Strange thing is since that, which was followed by a 2 mile drive home, it hasn't used any water this time.

I think the issue is it's overheating rather than leaking, but I don't know why.

#6 And617y

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Posted 12 July 2011 - 07:46 PM

the expansion tank is a possibility ,common! could be rad, get the rad pressurised maybe too much pressure there.

until you do them, fill up expansion tank ,test coolant mix.. 50/50 above do asap mate

#7 Rob-

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Posted 12 July 2011 - 07:53 PM

Could have cooked the head the first time you ran it with low coolant

#8 kib

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Posted 12 July 2011 - 07:55 PM

have you checked the water pump or may be the thermastat.have you looked at dip stick to see if water is
going in sump.

#9 coolcity

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Posted 12 July 2011 - 08:34 PM

No water in sump, engine is fine but it's the possibility of losing that which concerns me. Am proper broke at the moment after paying for the rad to be replaced (and given that fact, I doubt that both the old and new rads would have been at fault). Water pump is running. I've been wondering about the stat too but my understanding was that BMW stats have a failsafe on them?

#10 mboon

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Posted 13 July 2011 - 06:21 AM

losing smoke from the exhaust?

#11 CliffThomson

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Posted 13 July 2011 - 07:37 AM

Check in this order.

1. Fusebox, the rightmost of the big fuses. Often known to blow, this will stop the cooling fan working, your engine will overheat and blow water out via the expansion tank.
2. Unplug the connection to the fan (left hand side top of radiator) and run 12v to it, to check it's functional. this also causes this issue (I had a similar issue on my 318 for a while)
3. Make sure the cooling system is bled properly, so heating up full, top up with radiator cap off, keep filling til level stabilises, then check again after you've checked 1 and 2 above.
4. As others have said, check for leaks. But 1 and 2 on this list can cause exactly the problem you describe, in my case fixed with a 50p fuse from halfrauds.

Regards.
C.

#12 simonlpearce

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Posted 13 July 2011 - 08:56 AM

Personally i think you should replace everything - Rad, Expansion Tank, Thermostat, Water Pump. Its part of the general maintenance schedule so to not do it is to run a risk of further damage.

What mileage/age is the car?

#13 coolcity

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Posted 13 July 2011 - 05:03 PM

As per OP, it's an E46 318i, 53 plate, 65k miles so well below average mileage and has always been well looked after.

The original, ahem, "mechanic" did get back to me today (via text message) and said "it might be worth checking the thermostat" according to his mate at BMW. :rolleyes:

Anyway I took it into my regular garage, I'm self employed so no use to me not running right or waiting for some prat to try and guess what's wrong with it. The garage suggested replacing the stat which didn't open after running it for 20 mins on idle, said if it isn't that it's probably the head gasket though it runs fine and the oil is as it should be, nothing else in there as far as I can tell, so hopefully a new stat will cure it.

Rad had been replaced anyway now (see earlier posts) but rather pi$$ed off at paying out for something I probably didn't need at this moment in time as I really can't afford it, things a bit tight at the moment.

#14 Zimmer

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Posted 13 July 2011 - 09:54 PM

Apologies if skim read but hey

If its ran with low coolant check head gasket and head itself, I had this problem on my 318 and my head warped due to engine overheating :(

Hope you get it fixed soon and at not too much cost

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#15 coolcity

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Posted 14 July 2011 - 02:00 PM

I will be very surprised if there is any engine damage, the temp gauge has only risen once to just under but never into the red - and I shut it down straight away. Surely they're made of a bit better stuff than that, and isn't the red zone of the temp gauge there to warn of possible further damage before you actually do any?

I've been very careful to keep topping up and not let it get too hot or go too far in the few times I've been out since I was aware of the issue. Anyway I should know whether it's the stat or not in the next couple of hours. It's in a small independant garage, longstanding local reputation and he always seems to know what he's talking about so I'm as confident as I can be at this point.

All advice has been welcome though, many thanks to everybody.

Edited by coolcity, 14 July 2011 - 02:01 PM.


#16 simonlpearce

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Posted 14 July 2011 - 02:42 PM

I agree, id be amazed if it is the head - i stand by my previous post though that you should replace the whole system. You could end up replacing the stat only to find it puts extra strain on your weak old expansion tank which will be next to go.

That said i would also get the mechanic to check everything was fitted back together correctly after you rad change, there is a good chance you have a pipe not connected properly or something similar.

#17 coolcity

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Posted 14 July 2011 - 05:58 PM

I agree, id be amazed if it is the head - i stand by my previous post though that you should replace the whole system. You could end up replacing the stat only to find it puts extra strain on your weak old expansion tank which will be next to go.

That said i would also get the mechanic to check everything was fitted back together correctly after you rad change, there is a good chance you have a pipe not connected properly or something similar.


Well it's sorted!

It was the stat all along. The garage have pressure tested it and checked everything, drained and flushed it and refilled with coolant (since it wouldn't have had any left in it by now anyway). I wasn't able to collect it tonight, they only rang me 5 minutes before closing - if I could get there in five minutes I wouldn't need a bloody car would I? - but at least it's done.

I was a little surprised at your original post to be honest, maybe it's my naivety but I would be extremely surprised to find anything other than a very tiny percentage of car owners who replace all those items at 65k miles as part of a general maintenance schedule, though I see your point. The garage actually remarked that everything was in very good order for the age of the car. The expansion tank actually looks quite new although I've had the car for four years now. That said it's been washed down a few times lately! :D

#18 Zimmer

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Posted 15 July 2011 - 11:20 AM

Well it's sorted!

It was the stat all along. The garage have pressure tested it and checked everything, drained and flushed it and refilled with coolant (since it wouldn't have had any left in it by now anyway). I wasn't able to collect it tonight, they only rang me 5 minutes before closing - if I could get there in five minutes I wouldn't need a bloody car would I? - but at least it's done.

I was a little surprised at your original post to be honest, maybe it's my naivety but I would be extremely surprised to find anything other than a very tiny percentage of car owners who replace all those items at 65k miles as part of a general maintenance schedule, though I see your point. The garage actually remarked that everything was in very good order for the age of the car. The expansion tank actually looks quite new although I've had the car for four years now. That said it's been washed down a few times lately! :D


Glad its all been sorted, many more miles happy motoring now :)

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#19 kib

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Posted 15 July 2011 - 07:31 PM

glad you got it sorted allways simple things that baffel us.

#20 coolcity

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Posted 15 July 2011 - 08:11 PM

Glad its all been sorted, many more miles happy motoring now :)


Let's hope so. To be fair it is the ONLY problem I have ever had with the car. Everything else has been just general maintenance/wear and tear so I can't complain really.

The garage were more than fair too, only charged me an hour's labour on top of the price of the stat and coolant which I know was correct. Had I gone there in the first place it would have cost me £40 less than I paid needlessly to have the rad changed, but a valuable lesson learned - and at least I have a new rad.




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