overheating z3...

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Z3Jeremy
Joined: Sun 23 Jun, 2013 08:40
Posts: 71

  Z3 roadster 1.9i

overheating z3...

Post by Z3Jeremy »

Howdy Folks,
This is a top notch site that definitely enhances the z owning experience so thankyou to all contributors!- my z3 has been off the road for a few months but when I run the engine for a few minutes the temp gauge goes all the way to hot v quickly, the engine overheats but the radiator/header tank is stone cold! any pointers as to what this fault may be will be very much appreciated - I have recently gone thru the car cosmetically and basic maint but havent touched cooling system. Thankyou, Jeremy.
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Robert T
Site Admin
Joined: Mon 12 Jun, 2006 10:35
Posts: 10170

  Z3 roadster 1.9
Location: Cheshire

Re: overheating z3...

Post by Robert T »

Hi and welcome to the forum, Jeremy.

It sounds like the thermostat has failed in the closed position on your car, which would mean that the coolant stays within the engine and gets very hot and does not get pumped through the radiator to cool it down. The normal failure mode for Z3 thermostats seems to be to fail in the open position, which means that car takes a long time to warm up, however I note from your profile you have a facelifted 1.9, which I think will have an electric thermostat, so this may fail in a different way than the mechanical ones. The only other possibility I can think of at the moment is waterpump failure, which would mean that the coolant would not be being circulated at all, though I'm not just sure what other symptoms to look out for that would tell you that was the case.

Hope you get it sorted soon. I'm sure there will be some other ideas posted shortly.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2225

  Z3 roadster 1.9

Re: overheating z3...

Post by BladeRunner919 »

Could possibly be a blocked radiator too, but I'd start with Robert's suggestions and take it from there. I assume the basics, like coolant level, are ok and that there's no air in the system, as far as you can tell?
Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2093

  Z3 roadster 2.8
Location: Daglan, France

Re: overheating z3...

Post by Mike Fishwick »

Is the cylinder head really very hot, or is it just a guage malfunction?
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kkkrisss
Joined: Thu 13 Jan, 2011 09:15
Posts: 189

  Z3 roadster 1.8
Location: Munich

Re: overheating z3...

Post by kkkrisss »

U can also check the hoses that go to the radiator...
If they are cold then there is probably a problem with your thermostat...
Z3Jeremy
Joined: Sun 23 Jun, 2013 08:40
Posts: 71

  Z3 roadster 1.9i

Re: overheating z3...

Post by Z3Jeremy »

Cheers Chaps,
Definitely some handy hints to try out so thankyou to all respondees - is that a word?? the cylinder head gets very hot so will check the hoses and the thermostat, now I come to think of it when the car was last on the road the heater seemed very reluctant to emit any noticable heat so maybe this would suggest the thermostsat is faulty (Major!), yes my z3 is year 2000 engine 1.9 and I absolutely love it, had it for several years now and before this had a Z4 which although has a very nice interior the sharp handling just isnt suited to Dorsets leafy lanes. How would I best check for or remove air from the cooling system please before I start disassembling the flux capacitor...

Regards all, Jeremy.
Brian4
Joined: Mon 19 Dec, 2011 19:02
Posts: 541

  Z3 roadster 3.0i
Location: Hinckley

Re: overheating z3...

Post by Brian4 »

Unless you have had to drain the system recently there shouldn't be an airlock in system. If you check the expansion tank is full to the correct level and squeeze the top radiator hose a few times with the filler cap off you should see the water going up in the expansion tank.

I would think it is the thermostat or the water pump. BMW ones of your age had a plastic impeller which didn't fail by breaking up but sometimes came detached from the drive shaft so everything spins ok but the impeller does not go round.

To check both is a full drain and remove so you may as well replace both, flush the whole system through and refill with new anti freeze or ask your local garage to do it.
Brian
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Z3Jeremy
Joined: Sun 23 Jun, 2013 08:40
Posts: 71

  Z3 roadster 1.9i

Re: overheating z3...

Post by Z3Jeremy »

Thanks Brian,
That all seems to make sense, day off for me tomorrow so thats the mornings entertainment taken care of - will see what I can glean from the knowledgebase in a bit and take it from there. Off to the shed to dust off my mole grips AND my claw hammer!! Should do the trick...

Cheers, Jeremy.
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: overheating z3...

Post by Del »

The combined fact that water wasn't previously getting pushed around your heater and is now not apparently even being pushed around the radiator, I would have a £1 each way bet (last of the big spenders :D ) that it is the water pump. I've been changing thermostats since the 1970s and only ever experienced ones that stick open and result in colder running.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: overheating z3...

Post by Southernboy »

My 10p worth.....since you're doing the thermostat, you may as well change the thermostat housing to an aluminium one. The OEM housings are made of a hard plastic, which also becomes brittle over time and may crack when you re-fit and torque the bolts. There are waterpumps available with aluminium impellers vs the OEM plastic, which will ensure a longer life. Finally, only use distilled water when you re-fill the system...it'll prevent any scale build-up in the motor etc. The Thermostat housing will also need a new gasket and some gasket sealant will give you peace of mind too... :wink:
"Normal is overrated"
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