Hmmm, E39 overheating again
Discussion
Some time ago, my E39 528 was overheating and I replaced the water pump and thermostat, bleed it and all was well in the world again.
The car has done 4000 miles since then and all has been fine until today. First thing I noticed was that the cabin air went cold and then a few moments later, the temperature gauge started heading up. I pulled over and the temperature gauge quickly dropped back down to the middle and the heat returned. I finished the journey (another 2 miles with no issues. On the return trip, same thing happened. Pulled over, temperature dropped down, heat returned, continued home a couple of miles problem free.
I've been doing some investigating tonight. First thing to note was that the top hose was highly pressurised. I lost a lot of water taking the tank cap off such was the pressure in the system. The water in the coolant tank looks clean and free from oil. The oil cap looks clean and the exhaust doesn't seem to be expelling much in the way of white smoke.
When the car is idling with the tank cap off and bleed screw out there are no bubbles coming through to the coolant tank but after some time I do get a fair bit of water coming out of the bleed screw at low pressure. This seem a little intermittent.
I am very worried that this is cylinder head gasket failure but I would love some other theories. One concern is that when I replaced the stat, I used a pattern part and I've read a lot since about always using a genuine one. If that had stuck closed, it would explain many of the issues but I can't understand why air would be getting in causing the heater to blow cold?
The car has done 4000 miles since then and all has been fine until today. First thing I noticed was that the cabin air went cold and then a few moments later, the temperature gauge started heading up. I pulled over and the temperature gauge quickly dropped back down to the middle and the heat returned. I finished the journey (another 2 miles with no issues. On the return trip, same thing happened. Pulled over, temperature dropped down, heat returned, continued home a couple of miles problem free.
I've been doing some investigating tonight. First thing to note was that the top hose was highly pressurised. I lost a lot of water taking the tank cap off such was the pressure in the system. The water in the coolant tank looks clean and free from oil. The oil cap looks clean and the exhaust doesn't seem to be expelling much in the way of white smoke.
When the car is idling with the tank cap off and bleed screw out there are no bubbles coming through to the coolant tank but after some time I do get a fair bit of water coming out of the bleed screw at low pressure. This seem a little intermittent.
I am very worried that this is cylinder head gasket failure but I would love some other theories. One concern is that when I replaced the stat, I used a pattern part and I've read a lot since about always using a genuine one. If that had stuck closed, it would explain many of the issues but I can't understand why air would be getting in causing the heater to blow cold?
Your radiator has more than likely had it, the bottoms bow out basically under pressure which then seems to over pressurise your top hose and make it balloon.
New top hose required (now stretched replace it before it blows)
New radiator from C3BMW? They sell OEM radiators, do not get an EIS radiator, it wont fit and it will leak.
Took me ages to notice mine was leaking because of this, the sides push out and it leaks.
Then bleed it, apparently they are really hard to bleed but I have yet to have a problem, fill bottom hose up first, then fill top hose, then expansion tank, then run it up with heaters on.
Might I also advise you get a new cap from BMW as well
New top hose required (now stretched replace it before it blows)
New radiator from C3BMW? They sell OEM radiators, do not get an EIS radiator, it wont fit and it will leak.
Took me ages to notice mine was leaking because of this, the sides push out and it leaks.
Then bleed it, apparently they are really hard to bleed but I have yet to have a problem, fill bottom hose up first, then fill top hose, then expansion tank, then run it up with heaters on.
Might I also advise you get a new cap from BMW as well
pits pretty much has it covered but I'd also enquire about whether the car is losing any water (apart from out of the expansion tank cap!). I've been through all of this on my E34 and I replaced the 'stat and housing and the radiator. Water pump had a metal impeller and looked recent.
HustleRussell said:
Boiling water bubbles! I wouldn't discount a cracked head or head gasket just yet, but hopefully your problem lies elsewhere. A compression test might be prudent before you spend big bucks at a garage though (unless you're DIY'ing)
It'll definitely be a DIY job. The car just isn't worth enough to throw money at it which is a shame as it's a glorious old thing. I'll give the radiator a good eyeball tomorrow. If it looks okay, I'll see if the garage up the road can do a compression test as I really don't fancy driving it more than a mile or two.By the way, I had loads of problems with my BMW overheating when I first pressed it into service after the previous owner had barely used it for 3 years... the whole thing was kicked off by a bad expansion tank cap (which looked fine). I'm pretty sure the resulting air locks and overheating stressed my 17-year old radiator to death (they don't last much longer than 100k/ 10 years anyway apparently)
Just when I thought I'd cracked it with a new 'stat and housing and expansion tank cap, It continued to lose water and a leaky radiator was the cause. Surprisingly hard to spot until I removed the trim around the radiator. Unfortunately when I finally discovered the leak I was supposed to be towing the Caterham to Cadwell park so I had to perform a nasty bodge to make it drivable. It was a nail-biting drive but we made it and the car was awarded a new radiator upon our return. 100% fine since, haven't topped up the coolant since September.
Just when I thought I'd cracked it with a new 'stat and housing and expansion tank cap, It continued to lose water and a leaky radiator was the cause. Surprisingly hard to spot until I removed the trim around the radiator. Unfortunately when I finally discovered the leak I was supposed to be towing the Caterham to Cadwell park so I had to perform a nasty bodge to make it drivable. It was a nail-biting drive but we made it and the car was awarded a new radiator upon our return. 100% fine since, haven't topped up the coolant since September.
Cheers. Glad to hear it's not just me who has these problems. My 330 was a nightmare for the first year of ownership. The cooling system was never right. All works now luckily.
One thing on the E39 that is confusing is why the car should be okay at idle but not when moving. Seems strange.
One thing on the E39 that is confusing is why the car should be okay at idle but not when moving. Seems strange.
When I first went on the BMW 5-series owners forum complaining of cooling problems, some seasoned BMW folk told me to 'replace everything in the cooling system, it's all knackred at 100k+ miles'. I took this to be hyperbole and set about doing one bit at a time! ended up 'fixing' the system several times. I've learned my lesson now!
re: problems only occurring at above idle- not sure on that! I hope it doesn't indicate a cracked head or gasket.
P.S. Thermostat and housing is best bought from BMW. I had a leaky aftermarket housing and I wouldn't trust a simularly aftermarket 'stat.
re: problems only occurring at above idle- not sure on that! I hope it doesn't indicate a cracked head or gasket.
P.S. Thermostat and housing is best bought from BMW. I had a leaky aftermarket housing and I wouldn't trust a simularly aftermarket 'stat.
Could not echo Russ enough, get genuine BMW cap and thermostat housing, same with coolant and just about everything.
As for the whole idle thing, the engine isn't under load as such, and the fan is always spinning, put it under load more heat, water moving faster etc.
you wont see much on the radiator at all, it occurs randomly I found, you also can't really see anything wrong until you get the rad out, even then it is hard to see....I've done like 3k miles on a dodgy rad, 90% of the time it was fine, then every now and then it would just dump all of its water out the corner of the radiator, I can't explain how or why.
if you look at a radiator like this
|------|
|------|
Normal radiator^
Now a radiator after about 100k miles on an E39, but with less severe angle.
|------|
/------\
Try and get a BEHR radiator (OEM IIRC) got to BMW get a new radiator cap (£8) new thermostat housing like £30 if that, some coolant and a thermostat, water pump I forget now if you changed yours, make sure it has metal blades not plastic.
As said, bleed system, I fill left hand hose up first with coolant and then water, I then fill top hose into engine with coolant only, then put together and fill the expansion tank up, it minimises air in the system, some say put the heaters on with ignition, which I do, I then start the car and bleed it using the valves.
But for the love of god don't use an EIS radiator, I did poured water in, fell straight out....replacement doesn't seal properly and they don't fit for f
king st.
As for the whole idle thing, the engine isn't under load as such, and the fan is always spinning, put it under load more heat, water moving faster etc.
you wont see much on the radiator at all, it occurs randomly I found, you also can't really see anything wrong until you get the rad out, even then it is hard to see....I've done like 3k miles on a dodgy rad, 90% of the time it was fine, then every now and then it would just dump all of its water out the corner of the radiator, I can't explain how or why.
if you look at a radiator like this
|------|
|------|
Normal radiator^
Now a radiator after about 100k miles on an E39, but with less severe angle.
|------|
/------\
Try and get a BEHR radiator (OEM IIRC) got to BMW get a new radiator cap (£8) new thermostat housing like £30 if that, some coolant and a thermostat, water pump I forget now if you changed yours, make sure it has metal blades not plastic.
As said, bleed system, I fill left hand hose up first with coolant and then water, I then fill top hose into engine with coolant only, then put together and fill the expansion tank up, it minimises air in the system, some say put the heaters on with ignition, which I do, I then start the car and bleed it using the valves.
But for the love of god don't use an EIS radiator, I did poured water in, fell straight out....replacement doesn't seal properly and they don't fit for f
king st.Thanks once again for taking the time to help. Some great info here. If I do replace the radiator, I will definitely be following your advice. In the back of my mind is still the possibility that the head is cracked or the gasket has failed so I think I need to get the car to a local garage for a compression test before splashing out on parts. Fingers crossed that it is just the radiator. If it is that, I think I'll pop a new stat in at the same time as it bothers me that I didn't get a genuine one last time.
Your post has just sent shivers down my spine as it brings back a nightmare I had for about 5 months.
I am saying you have a small water leak somewhere(if you lift the bonnet can you detect a slightly fishy smell?)
The water level drops in the expansion tank over a few days then air is drawn into the system and it is an air bubble circulating that gives all the problems and odd readings.Refill the expansion tank and with the engine running you crack open the bleed screw on top of the rad(you need a broad blade screwdriver)and air and bubbles will come out. Stop when the water runs clear. Now to find the water leak. Mine was a weeping thermostat housing gasket and second time was a pin prick hole in a hose at the top rear of the engine.
I am saying you have a small water leak somewhere(if you lift the bonnet can you detect a slightly fishy smell?)
The water level drops in the expansion tank over a few days then air is drawn into the system and it is an air bubble circulating that gives all the problems and odd readings.Refill the expansion tank and with the engine running you crack open the bleed screw on top of the rad(you need a broad blade screwdriver)and air and bubbles will come out. Stop when the water runs clear. Now to find the water leak. Mine was a weeping thermostat housing gasket and second time was a pin prick hole in a hose at the top rear of the engine.
honestbob said:
Your post has just sent shivers down my spine as it brings back a nightmare I had for about 5 months.
I am saying you have a small water leak somewhere(if you lift the bonnet can you detect a slightly fishy smell?)
The water level drops in the expansion tank over a few days then air is drawn into the system and it is an air bubble circulating that gives all the problems and odd readings.Refill the expansion tank and with the engine running you crack open the bleed screw on top of the rad(you need a broad blade screwdriver)and air and bubbles will come out. Stop when the water runs clear. Now to find the water leak. Mine was a weeping thermostat housing gasket and second time was a pin prick hole in a hose at the top rear of the engine.
Does sound like it could be a pain to trace a small leak but if the head and gasket are fine I think the next step for me will be to replace all the remaining parts of the cooling system that I didn't touch last time (hoses and radiator) and hopefully, if it is a leak, I'll unwittingly fix it as I go. First thing I'm going to do is a sniffer test on the header tank. I figure that if there are exhaust gases present in the header tank then one way or another it's game over for the engine.I am saying you have a small water leak somewhere(if you lift the bonnet can you detect a slightly fishy smell?)
The water level drops in the expansion tank over a few days then air is drawn into the system and it is an air bubble circulating that gives all the problems and odd readings.Refill the expansion tank and with the engine running you crack open the bleed screw on top of the rad(you need a broad blade screwdriver)and air and bubbles will come out. Stop when the water runs clear. Now to find the water leak. Mine was a weeping thermostat housing gasket and second time was a pin prick hole in a hose at the top rear of the engine.
I had a pinprick hole in a hose as well, which was a pain to find. It only leaked when the engine was warm and the heat had caused a little bit of expansion. The hole was next to the jubilee clip retaining the pipe, so I'd try and keep an eye out for vulcanising rubber hoses as well.
Interesting evening. When I got home from work, I had a look through the car's paperwork and found out that the rad was replaced only 6 months ago at a main dealer so it seems unlikely that it has died. So I thought I'd try and bleed some air out of the system. Following the heating/block loop bleed, I got the car up to temperature ready to get some air out of the radiator circuit. When I stopped the engine though I could hear a slight hissing from under the bonnet. I tried to pin point it by ear and narrowed it down to the thermostat area. Although it looks a little wet around the upper part of the housing I couldn't actually see any water dripping out however I did notice this, see below. This is a photo taken looking side on at the thermostat from the passenger side of the car. You can see that there is a gap opening out between the plastic housing's flange and the aluminium flange, by the way that bit in the ali casting isn't a crack despite how the photo makes it look! I guess this could be my problem? I suppose it could also be a symptom of over pressure in the system but I would expect a hose would go pop long before this happens?
Unfortunately I didn't get any further as I'd have needed to remove the viscous fan and I didn't have a 32mm spanner with me but tomorrow night I'll dig a little deeper. If this looks like my problem, I obviously need a new stat housing and I'll replace both hoses at the same time and maybe chuck a new stat in there to be sure. Sound sensible?
Unfortunately I didn't get any further as I'd have needed to remove the viscous fan and I didn't have a 32mm spanner with me but tomorrow night I'll dig a little deeper. If this looks like my problem, I obviously need a new stat housing and I'll replace both hoses at the same time and maybe chuck a new stat in there to be sure. Sound sensible?
I use a hammer and chisel to get my fan coupling off, I struggled with the 32mm spanner as I couldn't get any impact on it to crack off that old left hand thread.
'Stat, housing, hoses and all associated 'O'- rings and gaskets sounds like the way to go. Be sure not to over-tighten the housing. The 'Stat will have an arrow stamped into it and you are supposed to fit it with the arrow pointing upwards at the 12 'o clock position. I drilled a 3/8" hole in mine to aid bleeding- doubt it was necessary but I couldn't think of any drawbacks so I did it anyway.
Sorry if I'm teaching you to suck eggs here!
'Stat, housing, hoses and all associated 'O'- rings and gaskets sounds like the way to go. Be sure not to over-tighten the housing. The 'Stat will have an arrow stamped into it and you are supposed to fit it with the arrow pointing upwards at the 12 'o clock position. I drilled a 3/8" hole in mine to aid bleeding- doubt it was necessary but I couldn't think of any drawbacks so I did it anyway.
Sorry if I'm teaching you to suck eggs here!
HustleRussell said:
I use a hammer and chisel to get my fan coupling off, I struggled with the 32mm spanner as I couldn't get any impact on it to crack off that old left hand thread.
'Stat, housing, hoses and all associated 'O'- rings and gaskets sounds like the way to go. Be sure not to over-tighten the housing. The 'Stat will have an arrow stamped into it and you are supposed to fit it with the arrow pointing upwards at the 12 'o clock position. I drilled a 3/8" hole in mine to aid bleeding- doubt it was necessary but I couldn't think of any drawbacks so I did it anyway.
Sorry if I'm teaching you to suck eggs here!
'Stat, housing, hoses and all associated 'O'- rings and gaskets sounds like the way to go. Be sure not to over-tighten the housing. The 'Stat will have an arrow stamped into it and you are supposed to fit it with the arrow pointing upwards at the 12 'o clock position. I drilled a 3/8" hole in mine to aid bleeding- doubt it was necessary but I couldn't think of any drawbacks so I did it anyway.
Sorry if I'm teaching you to suck eggs here!
Thanks for that and thanks again to Pits. You're slightly teaching me to suck eggs as I had the whole thing in bits only a few months ago but I do appreciate your thorough reply and I'm sure it will be useful to others as well. Off to price up some parts.
Thanks again chaps.
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