2002 Z3 1.9 Still Overheating HELP???

[Toby G]

Hi Guys

New to the forum.

My love my Z3, but it certainly has been a pain in the ass.

A few months the car overheated and blew the head gasket and a few other bits.

I have had the engine re-built which cost me £1300

its runs great but it is still overheating once sitting in traffic for more than a few mins. I have to turn the heater on full blast to stop it.

The thermostat has been dismantled so water is flowing all the time but yet it still overheats.

But the strange thing is; it only does it sometimes. It can be in traffic for hours and be fine and then other times it will overheat in just a couple of minutes.

Any ideas what this might be and how to fix?

Thanks
Toby

 

[Jack Ratt]

Hello and welcome to the forum. Are you losing coolant ? have you checked that you haven't got a blockage in the water system or even an air lock ?
Which engine do you have ?

 

[t-tony]

Worth having codes read Toby. Does the cooling fan (electric) cut in? If I recall correctly the 1.9 doesn't have a belt driven fan?

Tony.

 

[Stevo7682]

Which 1.9 engine is fitted .
The m43 8v engine has an electric fan
The m44 16v engine has a viscous fan same as the 6 cyl engine.

 

[t-tony]

Cheers Steve

Tony.

 

[Stevo7682]

I've got one of each now tony
Mines an 8v and lynne's a 16v auto

 

[Toby G]

Hi Guys,

No the coolant is full.
The codes have been ready, there is nothing on there.

It must be the m43 engine as it has an electric fan.

The fan does kick in once up to temperature.

Any ideas?

 

[Stevo7682]

Warm the car up without driving it initally the 2 pipes into the bulkhead will heat along with the top right radiator hose ( internal heaters should start to blow wam )
Bottom left side radiator hose and radiator should remain cold after a period it will then open the thermostat and allow hot coolant through the bottom radiator hose and radiator itself.
After thermostat opens fully and coolant circulates all the hoses should be hot also the radiator should be evenly hot over entire surface ( check from outside of rad ) after that the cooling fan should kick in and out to control temp ( gauge should be half way blower on hot should be roasting)

 

[Toby G]

They guys who did my engine rebuild removed the flow stoppers in the thermostat, so the coolant is constantly flowing through the system. I will check the rest of those things in the morning and see where that gets me.
Thanks

 

[mrscalex]

The symptoms sound like a troublesome viscous fan.

Have you replaced that?

 

[Stevo7682]

The symptoms sound like a troublesome viscous fan.

Have you replaced that?

Its a m43 so no viscous fan its an electric one

 

[mrscalex]

Sorry, was looking on my phone. I missed half the thread.

 

[5harp3y]

They guys who did my engine rebuild removed the flow stoppers in the thermostat, so the coolant is constantly flowing through the system. I will check the rest of those things in the morning and see where that gets me.
Thanks

Thats not a sensible thing to do

I'd be putting a lot of pressure on your engine builder if you are still having problems after laying out £1300

You could have bought another 1.9 for that

 

[Grumps]

Totally agree with the above. You have outlaid a lot of money so the work should be guaranteed, if they arn't prepared to sort it out i'd be speaking with trading standards.

 

[raymond]

Has the radiator been replaced ? Has antifreeze always been used ? Been bled properly http://www.pelicanparts.com/BMW/tec...WATER-Draining_and_Filling_Cooling_System.htm

 

[mrscalex]

Are you sure the fan is kicking in when you get the issue? Perhaps there is an intermittent fault? I think you need to be 100% sure it is running when you get the issue. And check that it stays runnng.

If it’s the fan and I’m not sure what else it’s going to be then it can only really be a mechanical or electrical issue. On my air con M54 it seemed like the auxiliary fan was fine. But it cut out after a few minutes. It turned out the bearings were gone and seized up as they got warm.

On the electrical side I believe the DME is calling the shots rather than the system running off a simple sensor to fan direct relationship. The DME takes its inputs from various sensors. Reading up briefly I’ve seen mention of an O2 sensor as well as the main temperature sensor. It also polls vehicle speed, air con pressure and battery voltage. So it’s possible there are faults with any of these sensors/control circuits.

There is also as I understand a controller unit bolted to the fan assembly which may have an intermittent fault.

And it might just be a DME fault. It’s not impossible the control pin is corroded and provides an intermittent signal. Or that the circuit board inside has an issue.

The above info was gleaned from an E46 forum. But I’d be surprised if a Z3 was greatly different.

 

[colb]

Since you had the head gasket blow are you 100% certain they repaired it correctly and its still not blowing causing the overheating?
A garage should be able to do a sniff test to diagnose for a blown gasket.

If certain its not the head gasket again then look at the basics, has it been bled properly?
Get the car as high as possible at the front using car ramps and heater set to hot, run the car with the bleed screw open to purge any air from the system.
Check the radiator is not blocked by draining it and flushing it backwards with a hose pipe
How old is the water pump, was the thermostat a new one or did they just mangle the original?
I would replace both for new items, then you know your starting with new parts that should be working ok.

 

[Lazzzydog]

Is it really overheating or could it be a faulty temperature sensor giving a false reading every now and again?
Did the " mechanic " even do a proper repair? No self respecting garage would bodge the thermostat. Get a second opinion from a trustworthy source to determine just what has been done for your £1300. It should be perfect for that sort of money.

 

[Nodzed]

Did the " mechanic " even do a proper repair? No self respecting garage would bodge the thermostat.

Absolutely agree! Why would they need to bodge the thermostat if the engine had been repaired and I'd be a bit naffed off if they didn't put a new one in anyway.

 

[Dickymint]

If a fault has been fixed why bodge something? even if its not been fixed it should not be bodged thinking about it I cant see any reason a competent garage would need to do this then let the customer have the car back, If I was you i'd take the car elsewhere and get the problem diagnosed just so you know where you are, people on here could speculate but you have a unknown now because you cant be sure its been repaired properly so you have little choice unless you start replacing random stuff like thermostat and radiator ect when it maybe the head is warped or not tightened properly or whatever....

A friend of mine replaced his whole cooling system changed head gasket ect only to find the Cat had broken up and somehow was overheating the engine