Z3 overheating

[donkeyday]

Oh please someone help me out with this ! My 2001 1.9 z3 has overheating issues ! Recently replaced rad, water pump, expansion chamber! Reconditioned head and head gasket! If I drive it for more than 10 minutes without the heater set to half way and fan on about the 2nd speed the temperature guage will creep upto the red ! It will drop to half way if I turn the blower to full and heater to max ! Obviously not ideal! This was happening before it blew a head gasket and cracked the head ! Would a faulty thermostat cause these symptoms?! Hoses look ok !

[nevan]

Yes, stuck closed thermostat can do that. But air in the radiator (bulp the radiator) or faulty fan clutch can also be possible cause too... So be sure to check them too.

[donkeyday]

Thanks ! Fan clutch has been done away with and just has the electric one !

[Mr Bingley]

If it were mine, and I already had to replace a head gasket do to an overheating issue, and unless I knew I had fixed the exact proven cause of the original overheating, I would replace every single component in the cooling system, except the heater core and valve (which apparently work), right down to every single hose, hose clamp, plastic fitting, switch, sensor, fan, etc. Certainly the thermostat should have been replaced when doing the head. Sounds like just deleting the mechanical fan has not worked for you--either replace it, or add an electric puller fan and full shroud.

[donkeyday]

Thanks for the advice! Read a lot about people ditching the clutch fan and fitting an aux fan to these and other models ! Can't be too serious is what I'm hoping because most of the parts have been replaced, apart from the stat and hoses ! Hoses look ok so will start with the stat ! Just seeing if anyone else has had the same issue and able to control the over heating with the heater and fan !

[z3forlife]

Pull the top hose and fill with coolant while parked on a slope. Sounds like it's not fully bled

[Vintage42]

... 2001 1.9 z3 has overheating issues ! Recently replaced rad, water pump, expansion chamber! Reconditioned head and head gasket! ... This was happening before it blew a head gasket and cracked the head ! ...

If thermostat was not replaced, it could be that. But another cause could be incomplete bleeding of air.

... The important parts are: nose as high as possible, thermostat open, heater on, above 1500 RPM. Squeeze the hoses with engine warm and running. When air stops coming out of bleed screw, tighten it...

Why was the radiator replaced - did it leak?

Your first overheating was likely caused by low coolant from failure of a plastic part such as the radiator or other plastic parts. Low coolant caused the overheating which caused the head to warp which made the gasket leak.

You do not mention replacing the plastic connectors - the pipe under the intake, and the Y on the back of the head. They could be leaking and cause low coolant and overheating again.

[deni2s]

Just replace everything again, that should fix it

[donkeyday]

Yeah faulty rad and water pump ! Header tank also replaced ! Seems strange the heater will keep it from overheating! Will replace the thermostat next week and if it's still happening I'll replace all the hoses ! System was bled correctly! Thanks for the advice!

[rf900rkw]

So much crap information for such a short thread.

Point. The heater can keep the car cool enough. This means there is flow through the heater, indicating proper filling.


Point, you can't "replace everything again" when you didn't replace everything the first time.



Whenever there is a serious overheat, the thermostat must be replaced. I don't care if it's only a year old, or even five minutes old. Exceeding the upper temp limit of the stat design willcause physical damage and it will never work correctly again. Replace the damn thermostat like you should have done in the first place, and hope you didn't damage anything with your repeat overheats.

[BimmerBreaker]

Just replace everything again, that should fix it

Well you aren't wrong...

[donkeyday]

Oh thanks for your advice Randy albeit a little bit aggressive!! It was one overheat and got the temp down within seconds with the blower. Drove it again today and it didn't overheat with the blower on so hopefully didn't do more damage! As you seem to know what you're talking about and forgive me if I come across dumb with this question but if the stat is stuck closed does that mean there will be a build up of pressure in the rad if I can't flow around the engine and would that result in it dumping water out and possibly damaging the rad ?!

[Mr Bingley]

Oh thanks for your advice Randy albeit a little bit aggressive!! It was one overheat and got the temp down within seconds with the blower. Drove it again today and it didn't overheat with the blower on so hopefully didn't do more damage! As you seem to know what you're talking about and forgive me if I come across dumb with this question but if the stat is stuck closed does that mean there will be a build up of pressure in the rad if I can't flow around the engine and would that result in it dumping water out and possibly damaging the rad ?!

I don't think he's being aggressive at all--you had an overheat event serious enough to blow the head, haven't found the cause, didn't replace the thermostat when replacing the head gasket, and are continuing to drive it using the heater to try and cool it while it continues to overheat. I think he was in fact being quite gentle with you.

[donkeyday]

Well if you took time to read what I've said , you'd know it doesn't continue to overheat and the heater does keep it cool ! So come on genius what damage am I doing if it's not overheating?!

[MIKYZZ4]

Replace the thermostat, as you should have in the beginning,
Followed by a Proper bleed procedure,
Aggressive? I'd consider it more frustrating on my end!

[Vintage42]

... My 2001 1.9 z3 has overheating issues !... If I drive it for more than 10 minutes without the heater set to half way and fan on about the 2nd speed the temperature guage will creep upto the red ! It will drop to half way if I turn the blower to full and heater to max !...

Well if you took time to read what I've said , you'd know it doesn't continue to overheat and the heater does keep it cool ! ... what damage am I doing if it's not overheating?!

You did say it was overheating. To avoid that, your vigilance has become the thermostat, and the heater has become the radiator. You are risking damage if a situation occurs where you and the heater cannot keep the coolant temperature down.

[rf900rkw]

Aggressive? Meh, I have been a bit grumpier than usual.

Any time a thermostat is run extremely hot, it will distort the metal, the frame, or the bulb itself. I have also seem them push some wax out. All this adds up to a thermostat that will not open at the correct temp, open at the correct rate, and/or open the full distance. Anytime there is a serious overheat, the stat needs to be changed. It was either the cause, or the victim. Either way it's gotta go.

[donkeyday]

Lol only kidding Randy ! New stat has been ordered ! Thanks for the advice , thought it was a bit excessive replacing every hose even though I know they're not leaking didn't realise stats are so sensitive but I am only an electrician not a mechanic which I think is obvious!😂 Fingers crossed it sorts the problem!

[T.Dot E30]

Fingers crossed it sorts the problem!

Do what was said and report back, no need for luck.
They are simple systems, you just need to know what you are doing and not take short cuts.

[donkeyday]

Replaced stat this morning and everything seems fine ! Temp not going over half now without the heater on ! Happy days ! Thanks Randy ! Didn't have to replace all hoses or anything that even looks at the cooling system like everyone else was saying to do !! Only another 7 months till the summer to enjoy it 😂😂😂

[Vintage42]

Replaced stat this morning and everything seems fine... Didn't have to replace all hoses or anything that even looks at the cooling system like everyone else was saying to do...

And you did not have to replace those pesky plastic connectors like everyone else was saying !! Wait until you need to replace them. If it ain't broke, don't fix it!

http://www.318ti.org/forum/showthrea...hlight=cooling
http://www.bimmerforums.com/forum/sh...rom-underneath
http://www.bimmerforums.com/forum/sh...e-coolant-leak
http://www.bimmerforums.com/forum/sh...-4-cylinder-Z3

[LannVouivre]

You need to replace everything that's the original cooling system. It's all very old material (plastic and rubber) that cannot and will not last forever. If a plastic part fails, you can lose all your coolant and fry your engine again. Preventative maintenance is vital on these cars.

[donkeyday]

Exactly! Hoses look ok ! Cars only done 60k ! If I ain’t broke don’t fix it ! I very much doubt if I took it for a service at bmw they would say you need to replace everything connected to your cooling system!

[BimmerBreaker]

60k miles sure, but at least 15 years old...

[ProductUser]

Exactly! Hoses look ok ! Cars only done 60k ! If I ain’t broke don’t fix it ! I very much doubt if I took it for a service at bmw they would say you need to replace everything connected to your cooling system!

As you know, English (I lived there for three years) weather is not exactly kind to cars. A few pounds (pun intended ) of prevention seems prudent. Just my 2-pence (again, pun intended ).