still overheating - help!!

[spp320i]

Hi all,

Getting pretty fed up with my 320i overheating, so hope someone can help!

Since Christmas it's been overheating, although less dramatically now. The seal on my expansion tank had failed so that was replaced and so was the cap (Thanks zimmerbimmer). It was still overheating so I went and got another viscous coupling from GSF today and fitted that.

For some reason the viscous isn't cutting in when it reaches halfway on the temp guage. The one I replaced it for is only 9 months old anyway but it seemed like the logical thing to replace. It's possible that both couplings are faulty, but unlikely I guess.

Question 1 - what needs to get hot around the coupling for the liquid inside to work so it engages and goes "whoosh"?! It seems to lock on when I first start the car but not when it gets up to temp.

Question 2 - I've spotted a small leak around two hoses that attach to the side of the throttle body, but it's a tiny leak, it's not losing much coolant at all as the level in the expansion tank remains pretty constant. What are these hoses and where do they go? I have pics of these if needed.

Question 3 - What the hell do I try now? I'm short of cash and thought that replacing the coupling should do the trick, maybe time to get a third one from GSF?

I've previously flushed the radiator and there's no leaks or blockages. There's no air locks and the heaters run hot as they should. It also seems that running the heaters doesn't take away quite enough heat to keep it at a safe temp - that used to work a couple of years ago but my blower is a bit rattly now, have cleaned it out but it could do with replacing, but that's another point and separate from the general overheating issue.

The top hose to radiator gets nice and warm, and the bottom hose is cool, so I think that means the rad is working as it should.

Please help!? Sorry for the long post but the more info the better!!

Cheers,

Si

[blitz877]

have you changed the thermostat? have a block test done to see if its the head gasket

[topspark]

When you say the bottom hose is "cool" . What do you mean by cool in relation to the hot top hose ? if you get my drift? If bottom hose is cold / cool when up to temp i would say you aint pumping any water through the rad fast enough. There SHOULD NOT be a massive difference in temp between the top and bottom hoses.

lee

[spp320i]

Thanks both for your posts...

blitz877 - haven't changed the stat, was thinking that could be next on the list, can I get one from halfords or something, any idea how expensive? Don't think it's the head gasket though, no signs of oil and water mixing anywhere.

topspark - The bottom hose is a lot cooler than the hot top hose, I think this is true when it's up to temp. I thought this was how it should be though, the purpose of the rad is to cool the coolant no? Why would it not be pumping through fast enough? I only changed the water pump about 9 months ago and if it wasn't working then surely it would overheat really fast and I wouldn't get heat out of the heaters?

Keep it coming please guys, I'm falling out of love with my e30 and can't manage more than 20 mins driving before it gets too hot!

Si

[bmwe30mtech]

Can you feel water pumping in the radiator hoses? (if not, try a new water pump but its unlikely)

Head gasket is the other option. Have you ever replaced it? You could be getting exhaust gas into your cooling water, making it overheat (so you wont see mayo). Does it tend to overheat when your pulling away hard onto a moterway or up hill? If it overheats under force then probably the head gasket or cylinder head crack. Hopefully not this though.

Is your radiator old/corroding?

You could get some liquid which you put in the header tank, which changes colour if exhaust gas is present, but not 100% reliable. Try smelling the header tank, is there a sweet or exhaust/combustion smell?

[Alyman]

Cold bottom hose at proper running temperature could mean that the thermostat isn't opening as it should.

To check the viscous fan, try turning it by hand when the engine is cold. It should run quite freely. Start the car and let it get up to temperature, then shut it off again. Try turning the fan by hand once more - if the viscous fan is working then it should be noticeably more difficult to turn.

[delphincabby]

Is the engine actually getting to opperating temp or are you just going by the gauge????? the nut on the back of the gauge can become lose and give very high readings, which would explain your cold bottom hose yet gauge showing hot

[spp320i]

Thanks again for replies...

bmwe30mtech - I know water's pumping round the system because with the expansion tank cap off, the water level rises and falls (I think that suggests the pump's working). Not sure if I'd say I can feel it pumping through the hoses but I'd guess so because of the small leak at the two hoses by the throttle body. I've never had the head gasket replaced, and don't think it had been before I got it but couldn't be sure. I'm hoping it's not this or a cracked head, would rather try other things first! I think it overheats a bit quicker when driving hard, but not much, this is probably normal as the engine will get hotter when driving at high revs. Don't think exhaust gas is getting in either, there's no noticeable smell from the expansion tank.

Alyman - Is there a way to check the thermostat? I've heard someone mention putting it in boiling water? Would I need to get a replacement gasket for the housing before I try this though? As for the viscous, I'll have to check the resistance of the fan in daylight tomorrow, I don't think there's any difference, but I'm fairly sure it's not working right, as it doesn't seem to go "whoosh" when it gets above half temp as it should.

Anyone got a working viscous near me I could pinch for 5-10 mins?!!!!

Keep 'em coming!!

[spp320i]

delphincabby - just seen your post, thanks. I am only going by the guage, which does flicker a bit, but i'm fairly sure of it's accuracy. I leave the engine running for 10-15 mins and it gets up to half, which is about right I think, then it just keeps going up. Putting the heaters on does help a bit, which also suggests it's vaguely accurate!!

[delphincabby]

Are your heaters RED hot when temp is high?

[spp320i]

Good question - the heaters don't seem to get as hot as they used to when the temp gets up to 1/2 or 3/4, and usually I turn the car off before it gets any higher, I don't want to crack the head! What you thinking?

[delphincabby]

Either thermo is not working or head is cracked/gasket needs replacing..... go with the cheaper option first, new thermo is only a fiew quid, but theck that nut also, i had this with my tourer and turned out to be a combo of viscous and lose nut on back of the cluster, mine used to get up to 3/4 then i'd turn her off, i replaced the cuplin but still kept goin upto 3/4 but i could see and hear the couplin cut in and shut off after a while, checked the nut and it was lose, did that up and sweet as a nut bang on 1/2 for the rest of it life

[spp320i]

Thanks delphincabby, I'm praying it is the thermostat then! Can I get one of these from Halfrauds? Don't know where else I can get one on a Sunday, and I can make it there in the car without overheating!

I will check the nut as well, how do I get to the back of the cluster?

I think my coupling may be knackered again, two in 9 months is just plain bad luck, but there is some discharge (ooer) on it which could mean the stuff inside is useless, thanks GSF! I haven't heard the new one cutting in so it may be faulty.

Do I need a new gasket for the thermostat housing? Reckon I can get one from Halfrauds as well or can I get away with using some gasket in a tube I have?

Any more for any more??!!

[delphincabby]

frauds do sell the thermo's and the blue gunk is fine just make sure its a dry and clean surface, get some one to give you a lift as there is nothing worse than tryin to work on a hot engine, all the time your movin it wont make any difference if the cuplin is workin or not..... so altho there may be a problem with the cuplin unless in traffic or just sat idling dont worry bout that till you can drive it with out it overheatin! on the move, once youve sorted that then sort the cuplin, at the mo your chasin your tail, internal heaters on hot and full wack will be ample for short periods in traffic or to test the thermo

[spp320i]

Thanks delphincabby, I'll get a lift down there and get a thermytwat. Should this keep the temp to about half when driving normally?

I'm fairly sure the coupling is useless as I just let it idle for ages to see if/when it would cut in and it didn't.

Anyone else...??!! All help appreciated. Will the thermostat solve the problem do we think?

[delphincabby]

yes fella will/should stay at opperating temp while driving normaly

[bmwe30mtech]

It should keep the temp about half when driving normally, or just below the half way mark.

Try the new thermostat, and if that doesnt work perhaps a new viscous fan if you think yours isnt working, if it still overheats i would double check for air locks and then consider head gasket.

Hope this helps

[spp320i]

Thanks all.

I just had to pop down to the shop and found that my viscous coupling has strong resistance when it's cold! Surely this isn't normal??

Halford have a thermostat for about £10, does this sound about right? I'm cautious of the idiots they have working there! My mate's on his way in an hour to take me down there so hopefully this will solve it! It better not be the damn head gasket!!

I also noticed on the way to the shop that the heaters were running cold! I know this suggests an airlock, but there shouldn't be as there wasn't a problem with the heaters yesterday. Does this also point to the thermostat?

I don't know where I'd be without this place!!

[bmwe30mtech]

Doesn't point to thermostat no.

That always suggests an air lock. Park the car on a hill (bonnet end facing uphil). Cut a water bottle in half, and then wrap electrical tape arround the bottleneck untill its a tight fit in the header tank opening. Then pour coolant into the bottle (and fill the bottle above the level of the header tank) while the einge is idling, this will get rid of ANY air! Then undo the bleed screw on the thermostat housing while the engine is running untill water steadily flows out (not air). This will all make certain there is no air lock.

If it still overheats, then do the thermostat, but you might as well do this anyway.

[spp320i]

Cheers for the reply, a bit strange behaviour at the moment. I'll do the thermostat first and drain all the coolant, then make sure I give it a good bleed to make sure there aren't any airlocks. I'll also clean all the hoses out and refit them to make sure there are no leaks, I guess this could cause an airlock if a hose is leaking. The two hoses next to the throttle body are leaking a little.

I've got no worries with bleeding, have had to do it a few times in my quest to sort out the cooling system. I'll try your method as well, not done that before, normally I just give all the hoses a good few squeezes to clear any air and then use the bleed screw.

Once I've done the thermostat and refilled the coolant and bled the system, I'll post with the results. I'm also going to check the nut on the back of the instrument cluster, as this could be a factor. I take it the steering column shrouds have to come off to do this?

I'll get her running properly again though if it's the last thing I do! It's only got about 14,000 miles to go before it hits 200,000 and I'm determined she'll get there - after that, I fancy a 2.7 build....!!

[bmwe30mtech]

No, the steering collumn bits stay on.

Remove under dash panel (the bit with headlight adjusters in it)
Then with your fingers feel for some hand tightened nuts up 'inside the dash' (you can reach up once the under dash panel is off) and these will release the black trim between the clocks and lower dash, you will see what i mean.

Then remove the panel arround the instrument cluster, two screws at top facing up int the dash, and 4 along the bottom (hidden at first by the trim you have just removed)

Then The screws holding the instruments are obvous. Have fun! Fiddly but easy.

I personally doubt this is the problem though!

[spp320i]

thanks bmwe30mtech.

I too doubt this is the problem, but I want to make sure the nut is tight as it should be, the temp needle has been a bit jumpy lately!

Thermostat first, refill and bleed, then check the cluster.

One thing that puzzles me (ok, more than one!) is that the top hose gets hot, but the bottom hose stays cold. This is strange, but perhaps means that the thermostat is only partly opening? Not sure if that's right, but if thermostat was stuck then surely the top hose wouldn't get hot at all??

[Stan0870]

hello mate, your right!, you can test the thermostat quite easily in a pan of boiling water, you will see the valve open, could save you a tenner!, you can also refit the housing oring too, if your carefull, if you say your water system has a slight leak, then that could cause over heating,even if you dont see water escaping, it will still be losing pressure, and as your cooling system is pressurised, this might be another option. is the top hose rock hard?.

[Martinaston]

Fix the throttle body hoses so they don't leak and then suck air back into the systm once it starts cooling down.
Fit a new thermostat.
Then buy a new radiator. 200k on the clock When was the last time it had a new rad ?

[spp320i]

stan0870 - too late, I've got the new stat now so am just going to fit it! May check the old one anyway just to see.
I'll refit the hoses to the throttle body and check that there aren't any leaks. The top hose is rock hard when it's hot.

Martinaston - See above. Don't want to get a new rad unless necessary, I've flushed it through and it seems fine. Nothing wrong with 200k though, German engineering at its finest!! Don't know if it's ever had a new rad but the current one doesn't look ancient.

[Brianmoooore]

Rads loose efficiency with age. 100k miles is replacement time.

[spp320i]

Thanks to everyone for their input.

I'm pleased to report that one thermostat later, the car is not overheating at all. I drove it hard for about 20 mins and it barely crept over the quarter mark, then left it idling outside for about half an hour, and it got to about half way between the quarter and half marks, so it's now slightly lower than it used to be.

This may also mean that the viscous is working, but who knows, it didn't even get to half so viscous wasn't needed it seems.

Also cleaned up the bits on the throttle body and refitted the pipes that were leaking, and now they're not leaking at all.

It's all bled nicely and the heaters are working fine.

I'll drive it through London next week when it's bound to get stuck in traffic for a bit and see how it behaves!

Thanks again,

si