Head Gasket Woes
- Thread starter McTyke
- Start date
I will get it checked by sniffer test or other to verify but pretty certain from my experience. I've worked in heat exchange business for over 40 years. In very early stages of HG failure there will be odd occasions where combustion gases get in to the cooling system for a milli-second. Cap can't vent this huge pressure in such a short space of time so the pressure finds another escape. I have seen radiators blown untill they are amost round. In my case got low coolant light driving home recently. Assumed it was cracked expansion bottle but no. Tried filling the system and water was pouring out of seam of radiator. Radiator leaks usually start small and just get worse. They don't just appear as massive leak. Replaced rad anyway and took it for a blast. Leaking now from some of the o rings that seal some of the hoses at bottom of rad.
Car has done 137k and since I replaced Vanos it has been fun to use all the performance which I do regularly. Was about to sell it as have been promoted and have company car. My Mrs want's me to punt it as I have been been quoted around a grand but its just not in me. Its a great car so will take the hit and then sell. Sorry for long response. Once work all done I will advertise. Everything that wil ever need doing to an old Z4 will then have been done.
Car has done 137k and since I replaced Vanos it has been fun to use all the performance which I do regularly. Was about to sell it as have been promoted and have company car. My Mrs want's me to punt it as I have been been quoted around a grand but its just not in me. Its a great car so will take the hit and then sell. Sorry for long response. Once work all done I will advertise. Everything that wil ever need doing to an old Z4 will then have been done.
Attleborough, Norfolk
I suppose the question is more: if it's not the head gasket, is there anything else that could cause these symptoms?McTyke said:
As they say, once you've eliminated all the impossibles, whatever is left, however implausible, must be the answer.
Let's hope you find a cheaper, more plausible answer.
I was just around seeing my man Colin at BMS. He know's his beemers and also saying M54 is pretty much bombproof and will take a lot of abuse. May be water pump failure - if its one with plastic impeller - could possibly cause overpressure without it showing overheating on temp gauge. As you say, it may be implausable but anything is possible with oldish cars.
The coolant system is under pretty high pressure on the z4. Do you know which o-rings exactly leak (point out on a diagram from realoem).McTyke said:
Some are prone to leak.
Radiators blowing up until they are round is a common failure on z3's (with the same or similar engine)
My guess is still leaks in the cooling system and not a HG failure. With high pressure cooling systems HG failures you can ususally smell.
It can also be that the hoses aren't seated properly. The click system can have a lot of friction. Also debris can get between the silicone rings; debris from within the coolant (sediment).McTyke said:
The O-ring on termperature sensor 13621433077 is a very common one to start leaking. You can replace that by using o-ring 13621743299 I believe.
Leaks on the waterpump shaft are difficult to see. I couldn't see them with a coolant pressure test kit; the shaft had to be spinning to actually see it leaking. Same goes for little cracks in the reservoir; they only leak when the coolant system is at pressure.
Just checked cooling system operating pressure as I ordered new cap. I knew it was higher than most other systems but 29 psi! At that pressure it is very likely that the old rad let go in a big way and that the old o rings were not good enough to hold that pressure with the new rad. I am now 99% confident it's not the HG. Can't wait to get new o rings fitted to confirm this. Watch this space 
As a comparism my old Impreza Sti would run at 13-15psi. I remember reading a great article about how BMW needed to increase cooling sytem pressure to cope with higher engine/cooling system temp (higher pressure increases boiling point) which caused rubber gaskets and plastics to fail down the line. We all know about that.
As a comparism my old Impreza Sti would run at 13-15psi. I remember reading a great article about how BMW needed to increase cooling sytem pressure to cope with higher engine/cooling system temp (higher pressure increases boiling point) which caused rubber gaskets and plastics to fail down the line. We all know about that.
After I had stripped out the rad again it was clear I had not seated the oil cooler thermostat properly. I had taken the precaution of ordering a new one (which was good as old one fell apart as I was taking it out - the plastic was so soft) I re-seated it properly and replaced several O rings in the hoses and pressure tested. All good. Several motorway blasts later and still holding. So not HG - thank goodness.
Car sold at the weekend to the mum of one of my sons pals so will still see it around. Hopefully not if there is any problems with it
Thanks for all advise. For the first time in my life I am now driving a brand new car, a high tech Discovery Hybrid so no tinkering at the weekends. Which I will miss. Will need to get a little project car to work on.
Car sold at the weekend to the mum of one of my sons pals so will still see it around. Hopefully not if there is any problems with it
Thanks for all advise. For the first time in my life I am now driving a brand new car, a high tech Discovery Hybrid so no tinkering at the weekends. Which I will miss. Will need to get a little project car to work on.
Believe me it was not an easy decision to part with it. Has to be the best fun/bangs for your bucks car I have ever owned. My daughter loves it but she can't get insurance until she is 21 and I just don't have anywhere to park or store it for 2 years. But I told her there will still be plenty of good ones on the market when she is ready.