Radiator and Overheating Problems

aerojamesz4 · Post by **aerojamesz4** » Thu Apr 28, 2011 10:11 am

Hey guys,

The other day I parked my car, walked away and heard a bang, only to see heaps of steam coming from under my bonnet. After the car cooled down, I put water in the radiator and it dripped out the bottom. The next day it was towed to a mechanic and I replaced the expansion tank for the radiator as the old one had cracked.

Today I was trying to use the heater in my car and found that only cool air was coming from the aircon. As soon as hot air started to come out the car overheated and I pulled over. I have put water back in the radiator and its leaking from right at the bottom from a silver hose/plug. Has anyone experienced this before? What is wrong with the car as the expansion tank is now new and the radiator itself was fine. Could it just be a connection problem? And why is the aircon not functioning properly?

Thanks for any help you guys can give.

ZetaTre · Post by **ZetaTre** » Thu Apr 28, 2011 6:18 pm

Looks like BMW well coordinated a global failure of the Z4 cooling systems!!!

After reading the first signs of the global conspiracy, I decided to play offensive and replaced the waterpump and thermostat over the weekend. I opted for the EMP Stewart WP that has a history of great performance; the thermostat is from Whaler, the OEM for BMW... Since I was at it I replace the tensioner, the 2 deflections pulleys and a new drivebelt. I've been wanting to do this for a while since I've noticed that coolant lever would always be on the low side: it was a weird leak. I would fill up to the proper level and it would quickly drop to a lower level and then stay there... What stopped me was the "special procedure" required on the Z4: lifting the engine... Lots of people jack up the powerplant from the oil pan. It works, but is risky: crack it or having a leaky gasket can happen. So I rented a cerrypick engine hoist, released the driver side mount, strapped a rope around it and lift it up that way. It turned out to work excellent!! In the US you can rent such tool from a company called Sunbelt Rental... Or worst come to worst you can buy one used from your local Craigslist and then resell it once the job is done... Or you can be ghetto and buy one from Harbor Freight tool and then return it... Whichever way you do it, I would recommend the engine hoist over the under-the-oil-pan-jack-method...

I was pleased with the job well done and in the process I discovered the actual source of the mysterious original leak: there is a hairline crack in the reservoir, right where the joint of the mold is above the return line for the coolant from the heater core...

Off to the dealer for the new part...

Anyway: best of luck!!!!

And for everyone else with the pre-face lift Z4, keep an eye on the cooling system... That is the notorious Achilles heal of th M5x... In my personal opinion and experience, the WP & t-stat tend to fail catastrophically, while the coolant level sensor gives you some sort of warning from the less catastrophic leaks from the radiator and expansion thank...

Godspeed everyone!!!!

Blue · Post by **Blue** » Sun May 01, 2011 4:51 pm

Everything I've read suggests that after a while you need to budget for a total overhaul of the cooling system on the M54, good luck!

I'm running two at the minute and praying that neither of them have any issues for a while!

LiverpoolFC55 · Post by **LiverpoolFC55** » Mon Sep 17, 2018 8:28 pm

Hi Guys my Z4 2.5I 2003 is ( touch wood ) running fine . I am only running short distances -five miles less than ten minutes of driving The temp needle is dead centre and it hardly uses any coolant or oil. All good so far. However when I garage the car I touch the bonnet and it is warm to hot- is this normal? If not is there any particular part that I need to be concerned with .The air conditioning works and so does the heating.

Smartbear · Post by **Smartbear** » Mon Sep 17, 2018 8:59 pm

LiverpoolFC55 wrote: ↑Mon Sep 17, 2018 8:28 pm Hi Guys my Z4 2.5I 2003 is ( touch wood ) running fine . I am only running short distances -five miles less than ten minutes of driving The temp needle is dead centre and it hardly uses any coolant or oil. All good so far. However when I garage the car I touch the bonnet and it is warm to hot- is this normal? If not is there any particular part that I need to be concerned with .The air conditioning works and so does the heating.

Hi, you you have no issues as the bonnet has no insulation underneath it does get fairly warm

Rob

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