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jonathanlewis19 
Newbie
Joined: 27-March-2003
Location: United Kingdom
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Points: 32
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 Topic: E36 328 overheating
Posted: 11-August-2005 at 04:02 |
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HI all!
I lent my car to my gf to drive backwards and forwards to work - last night, she calls me on the way home and says "what does it mean when the red light comes on in the bottom right of the dash?" Grrr....
Anyway, the AA towed me back and it's now at the garage...
I'd like your thoughts on what it might be....
Symptoms:
On idle, car heats up to slightly below normal and stays there.
On driving, the car stays bang on normal for about 1.5 miles, and then starts climbing pretty quickly (quickly enough to want to stop the car within a few hundred yards before it crosses the higher white line).
Inside the bonnet, the main fan is going round, the top hose is hot but the bottom hose is stone cold. Because of this, the vc isn't really engaging (not that i'm sure it would help) nor the aux fan. The aux fan does work, however, if the ac is on.
So - any ideas? thermostat, water pump or gunged up rad??
My thinking is that it's not the gunged up rad, because then (I think) I would have noticed things not being right as it gunged up... All was very very normal until last night...
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Peter Fenwick
Bavarian-Board Contributor
Joined: 27-August-2003
Location: Lost somewhere in time...
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Points: 6484
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Posted: 11-August-2005 at 04:05 |
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Could be the thermostat as they are know to give problems although they tend to stick open which would cause your car to take a long time to warm up not overheat. It's worth checking since it is fairly cheap to buy and an easy job to replace.
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Entering an age of Austerity and now driving a Focus Diesel.
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sleeper
Really Senior Member II
Original and STILL best
Joined: 26-March-2004
Location: East Sussex/Kent border
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Points: 2098
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Posted: 11-August-2005 at 04:09 |
Hmmm, far too common this.
sounds like an airlock on the thermostat.
Have you had the cooling system apart recently?
Have you bled the system for air?
If done the above I would recommend a new thermostat, a good flush out, nice new antifreeze and if you can afford it or if its in any way dicey, change the waterpump too.
Edited by sleeper
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pma1ums
Really Senior Member II
Joined: 12-October-2004
Location: central uk
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Points: 1148
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Posted: 11-August-2005 at 04:39 |
BMW Car Club (GB) Forums: e36 overheating
did you read this ????
could it be that?
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its a dogs world out there
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jonathanlewis19
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Joined: 27-March-2003
Location: United Kingdom
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Posted: 11-August-2005 at 04:44 |
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Thanks!! I don't think it is the viscous coupling on the fan for a few reasons:
The fan goes round when i start the engine. I tried stopping it using the 'newspaper test' and it shredded the newspaper.
With the engine stopped, if i spin the fan it goes around for only half a revolution.
This to me points to the viscous coupling itself being fine.
Also, I would have thought that the symptom of a poor vc would be that water would go straight through the rad without losing any heat - i.e., the bottom hose would be just as hot as the top hose. This isn't the case - the bottom hose is pretty cold as the needle climbs over half way and the top hose is almost too hot to touch (about as hot as putting your hands around a mug of freshly-made tea).
But thanks for your reply - I thought it could be that too...
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sleeper
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Posted: 11-August-2005 at 04:49 |
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sludge would be very unlikely BTW, if she's been run on neat water the quickest rout to sludge, (unlikely) your head would have started to perforate or the gasket would have gone by now.
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jonathanlewis19
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Posted: 11-August-2005 at 04:59 |
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gaskets are fine - oil is clean (almost suspiciously so, but perhaps because I'm used to classic english sportscars...) and there has been no coolant loss...
So it all seems to point to the thermostat... or an airlock in the system (which would be strange as the system hasn't been opened at all since the last service (about 8 months ago))
Edited by jonathanlewis19
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sleeper
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Posted: 11-August-2005 at 05:10 |
what year is your car?
I wonder if you have the plastic impellered waterpump...?
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LuxAuto
Senior Member II
Joined: 10-April-2005
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Posted: 11-August-2005 at 06:16 |
This is more likely to be thermostat failure, because the engine won;t just suddenly heaat up like that, especially when you've already confirmed that the fan is working fine.
Sludge build up or blocked radiator would result in gradual overheating over time. When thermostats fail, they ted to fail in the closed position because of the spring that is fitted to it and would give you a hot top hose and cold bottom hose, as the water is not being allowed to circulate.
It would also explain why the intial 1.5 miles is fine.
Air locks are unlikely, especially if you've not had the coolant system apart and don;t have any leaks. Are you leaking water? Even then, it is highly unliely that air will enter the system this way because of the positive pressure that is present in the system.
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jonathanlewis19
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Posted: 11-August-2005 at 06:17 |
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It's a late 1996 model which means (I think) that it got the metal impeller... Although I've seen conflicting information on this...
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sleeper
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Posted: 11-August-2005 at 06:34 |
 LuxAuto wrote:
This is more likely to be thermostat failure, because the engine won;t just suddenly heaat up like that, especially when you've already confirmed that the fan is working fine.
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I thought they failsafe open?!?
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LuxAuto
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Joined: 10-April-2005
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Posted: 11-August-2005 at 06:50 |
The thermostat?
If it failed in the open position, the engine wouldn;t be overheating, it would be overcooled and the heater would never get warm.
Most thermostats fail in the closed position because a mechanical spring is used to return the valve to the closed position.
A thermostat works on the principle of heat expanding the wax in the thermostat. As the wax is in a sealed unit, it has nowhere to go and the resulting pressure pushes against the spring, which opens the valve.
When the engine cools down, the wax contracts and spring pressure will force the valve closed. that's why a thermostat hardly ever fails in the open position, but it does happen, but the symptoms at the moment doesnt suggest this.
Edited by LuxAuto
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sleeper
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Posted: 11-August-2005 at 07:28 |
hmm, I think you are right regarding the operation.
Not very impressed that you are left open to engine damage because of the cheapness of a component by BMW though.
If they do work that way there is no failsafe.
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LuxAuto
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Posted: 11-August-2005 at 07:57 |
I think all thermostats are manuafactured that way, (wax) so BMW can't be blamed for being cheap.
Apart from the lack of a fail safe, it's quite cleaver and very simple. What i usually do, whenever I change the coolant, and depending how easy access is, is to replace the thermostat as well. On non-bmws, they only tend to be �5-7 so it's worth it and saves having to drain the coolant out again.
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jonathanlewis19
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Joined: 27-March-2003
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Posted: 11-August-2005 at 10:00 |
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I left it to the garage to sort out - they've just told me that they've taken the old thermostat out but not put a new one back in. They're telling me that the car will be fine without it, but will just take a little longer to warm up... Are they right? I'm worried
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LuxAuto
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Posted: 11-August-2005 at 10:38 |
No!
They are just bodging!
An engine runs at its most efficient when it is at a certain temp, usually in the 90s, this is where you get optimum efficiency. By taking the thermostat out, you no longer have any control over the temp of the engine. it will always run overcooled and will cause more wear and tear on the engine, plus the engine will consume more fuel fuel.
And in the winter, you can forget about having decent heating, especially if you drive on the motorway!
Other effects of overcooling will be an inability to burn off any moisture in the engine. This will increase wear and tear as it will destroy the oil and can cause pitting of the components due to water ingress.
You have every right to be worried.
Why can;t they put a new thermostat in? Don;t they have one?
Edited by LuxAuto
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sleeper
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Posted: 11-August-2005 at 10:40 |
that'll do your mpg the world of good. NOT.
your engine needs to get to temp as soon as possible and the maintain it. otherwise your economy goes up the spout on the m'way etc. and your oil runs cooler - thicker - harder work for the pump & gaskets at high revs.
Use a thermostat.
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jonathanlewis19
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Posted: 11-August-2005 at 10:45 |
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Well they've put it back together now, so that's kind of it done. The good thing is that I'll take it for a spin tonight - if it all stays at or below temperature, then I know that the problem was the thermostat - then I can just get them to put one back in... Expensive I know, but prob better than putting another one in, thinking it was fixed, bolting it all back up and then finding it was still f***ed...
Thanks for your advice though guys - will definitely get a new one put in once I know that it was just the thermostat that was the problem!!
You're all stars!
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sleeper
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Posted: 11-August-2005 at 10:46 |
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Goose
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Joined: 12-July-2005
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Posted: 11-August-2005 at 12:15 |
jonathanlewis19 wrote:
I left it to the garage to sort out - they've just told me that they've taken the old thermostat out but not put a new one back in. They're telling me that the car will be fine without it, but will just take a little longer to warm up... Are they right? I'm worried |
Thanks god for guys like these, and especially Lux. I wouldn't know what to do if they'd said I could drive the car without a thermostat.
Kin' Cowboy garages.
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E36 328 overheating
