Brrrrrrrr.... It's cold in here!

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I'm starting to think that BMW wasn't the issue after all...

Chances are that at some stage the radiator was replaced with an aftermarket one in which case the screw thread would be different. Not liking this can of worms I've opened up as I'm probably going to need to replace the radiator now as I can't see any markings or anything on this one that could identify it.

 

[zedonist]

Feel for you Andy, I learned the hard way too, now I don't start the job unless I have spare bits available, including surrounding parts that need removing

 

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Feel for you Andy, I learned the hard way too, now I don't start the job unless I have spare bits available, including surrounding parts that need removing

I like your approach and will definately be adopting it in the future. For the moment I think I'll do what I can to get the screw back in and watertight while I see about getting another radiator.

 

[Zeti]

Guys, for the moment it's not a tragedy! It's just a screw or in the worse case is a radiator! In this kind of situations I'll be happy it was happening home and not "in the middle of nowhere"........

 

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ok... Now I officially give up. I have gone beyond my level of knowledge and I'm stumped!

So what happened since yesterday...

Well I managed to sort the radiator bleed screw - no leaks or even the slightest hint of weeping...

Then this morning I decided to put some certainty behind the possibility of a faulty heater control valve behind me once and for all. After removing the appropriate hoses I completely bypassed it, leaving one hose as originally connected directly to the heater matrix and the other disconnected. I then connected the hose from the other end of the heater valve (the one that goes back to the engine) directly to the other connector of the heater control valve.

Checked coolant level (there had been minimal coolant loss from the hoses during the switchover and I had topped them up with coolant directly into the hose before refitting).

Checked that everything was nice and snug with no leaks and then started the car and observed for a few minutes - all ok, no leaks...

Went for a drive. After a few minutes the heater started to get warm but as has been the case in the past, when I idled at traffic lights it went cool again. Took it for a quick run along a section of the M5. During that the heat was really nice - not scorching but really nice. Got off the motorway and pulled into a side street idling - temp went down again :-(

I have to say that having disconnected the heater control valve seems to have made the temp get warmer quicker after idling but the really weird thing is this...

I though that the heater control valve worked in conjunction with the temp control dial in the car and expected the temp to be hot (or as hot as possible) all the time however - even when going along the motorway, and with the heater valve disconnected, if I turn the heater dial down to cold - the temperature of the air coming from the vents instantly goes cold. If that's the case, what's the point of the heater control valve in the first place???

Though I'd have rathered fix this myself, I think it's perhaps time to part with cash and have someone else fix it rather than parting with any more time *sigh*

 

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Did a little more testing (I know - I'm a sucker for punishment). While I still don't know how the temp dial could cause any changes in temperature with the heater control valve disconnected (unless there's a secondary one somewhere), when I drive the car and check under the bonnet, the hose to the heater matrix - the one on the right if standing facing the car which I think is the one pushing hot coolant into the matrix gets nice and hot to the touch. The one taking coolant away after it has gone through the matrix, while not cold is significantly cooler. I guess that this is normal behaviour (as the coolant would have been cooled somewhat after going through the matrix) but I'm not certain.

 

[t-tony]

The only thing possibly causing this would be a partially blocked matrix as the water " skims" across the end of the matrix instead of passing through the whole core of it.

Tony.

ps Have you flushed the matrix?

 

[jonco]

..................... The one taking coolant away after it has gone through the matrix, while not cold is significantly cooler. I guess that this is normal behaviour (as the coolant would have been cooled somewhat after going through the matrix) but I'm not certain.

This presumably was under `idle' condition which is when your problem arises - suggest you repeat test and rev the engine and see what happens to the return temp.

 

[oldcarman]

I agree with T-, flush that heater core and get a thermometer. The core should be back flushed as well as your heater valve. You may be shocked at what comes out. My heater puts out enough heat that even without a rear window in my soft top, it's too hot on my feet with the fan on 4. Trinity asked me to please turn it down. It's like that even at idle. JIM

 

[Barry Gadd]

Had a few cooling problems myself one ended up blowing a hole in the rad due to xs pressure probably from leaking headgasket caused by warped head. Had to have head skimmed plus new gasket but now that problem is solved (fingers crossed)
If the problem is due to trapped air unscrew the plastic bleed screw (the one you described - next to the filler cap) and check the water level. It should be about half way down the plastic expansion tank. The screw should be screwed fairly tight down. If it's spinning round then the thread must have been stripped and you won't have any retained pressure in the system when hot.
Park the car with the front as high as possible in order to get the top of the rad above any other coolant area,(up a slope or perhaps jacked up). remove the rad cap and squeeze the upper rad hose ,put your thumb over the bleed valve hole then release the hose. Repeat this several times checking the water level in the expansion tank regularly.
Make sure your heater control is on hot.....
When you get to the point where the water level isn't going down further you should have removed any trapped air.
Your problem does sound more like circulation than airlock but the above process may help and costs nothing.

Another check is to run the engine with the rad cap removed. At tickover you should see a dribble of water emerging from a hole inside the neck of the filler cap. If you rev the engine the dribble will become a jet...... I think this will indicate if the pump is working properly.

Good luck

 

[upstream]

Had a few cooling problems myself one ended up blowing a hole in the rad due to xs pressure probably from leaking headgasket caused by warped head. Had to have head skimmed plus new gasket but now that problem is solved (fingers crossed)
If the problem is due to trapped air unscrew the plastic bleed screw (the one you described - next to the filler cap) and check the water level. It should be about half way down the plastic expansion tank. The screw should be screwed fairly tight down. If it's spinning round then the thread must have been stripped and you won't have any retained pressure in the system when hot.
Park the car with the front as high as possible in order to get the top of the rad above any other coolant area,(up a slope or perhaps jacked up). remove the rad cap and squeeze the upper rad hose ,put your thumb over the bleed valve hole then release the hose. Repeat this several times checking the water level in the expansion tank regularly.
Make sure your heater control is on hot.....
When you get to the point where the water level isn't going down further you should have removed any trapped air.
Your problem does sound more like circulation than airlock but the above process may help and costs nothing.

Another check is to run the engine with the rad cap removed. At tickover you should see a dribble of water emerging from a hole inside the neck of the filler cap. If you rev the engine the dribble will become a jet...... I think this will indicate if the pump is working properly.

Good luck

Thanks. I do remember that when I removed the bleed screw and was idling not much happened but when I revved hard a jet of coolant shot up through it so it would appear that the waterpump is ok.

I ended up looking at some forums when I had a bit of time this afternoon (during my lunch break) and it appears that quite a few owners of Z3's have experienced the exact issue that I'm having. Some go as far as to put it down to a design fault and say that this is why with 1999 models onwards, they had a separate pump (electronic) to circulate coolant when the engine was idling.

I also spoke with a local mechanic. I may just drop it off there and get him to change the waterpump too - just to be certain. My understanding is that there are some "high flow" water pumps out there. I may see about grabbing one of those.

Having driven to work this morning, spending almost an hour in stop start traffic and with an ambient temperature of around 5 degrees C I'm more determined than ever to get this sorted as it really is taking the fun out of things at the moment.

 

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Update...

Had the car booked in for later this week. This morning however, towards the end of a short (9 mile) journey and being stuck in traffic for 90 minutes, the Z started to idle a bit weird. Then for no apparent reason the temperature gauge rapidly started to rise. I was able to pull into a hand car wash area when the gauge was on the notch above the half way one (not into the red but about half way there). I turned the car off and half expected to see a massive plume of steam come rushing out but nothing.

Five minutes later I started the car and it did so with no problem. I then started to finish my journey (less than one mile to go) and I noticed the temp gauge going up above normal but not quite as high as before. I parked it up at the work car park and left it until lunchtime.

Concerned that it may do the same thing in rush hour traffic on the way home, I decided to drive it 10 miles to the garage it had been booked into. I got in, started the Z up and it drove for 10 miles with no signs of overheating at all. The air temp was unchanged at just lukewarm when driving and cold when statonery. When I arrived the mechanic popped the hood and had a look around - No signs of overheating, no lost coolant - nothing. I said I'd like to have the heater matrix flushed and water pump changed. He said that looking at the thermostat housing and the water pump, it looked as if they hadn't been changed long ago so he felt that it wasn't needed. He would however look into things and get back to me.

ps... One thing he also did was rev the car hard (to around 5,000rpm) and said that if the waterpump had gone, it would have instantly boiled the coolant.

I'll keep you informed...

 

[zedonist]

I think you had an air lock after removing the pipes which caused your recent issue, but I do have to question now if you actually have a thermostat in your car, if the heater valve is not the problem

 

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I think you had an air lock after removing the pipes which caused your recent issue, but I do have to question now if you actually have a thermostat in your car, if the heater valve is not the problem

I "think" there's one in there due to with this morning being so cold I would have thought that without a thermostat, the engine temperature would have struggled to get to the half way point at all. It got there after about six minutes (which seems about usual). Also it has one of those plastic thermostat housings. Am I correct that the thermostat and plastic housing are one unit? I suppose if it is that there are always methods of splitting them perhaps.

It's all way beyond me now. I just hope that the mechanic can get to the bottom of it. I did try calling BMW but they wanted £50 just to have a look which at the moment I could probably have lived with to be honest - provided that when they gave their diagnosis and I went ahead with their suggestion that it actually achieved the result and I didn't end up back at square one but with a depleted bank balance ;-)

 

[Zeti]

The thermostat is fixed in two plastic clips in the housing.
I had a thermostat with a very strange behaviour: when starting the engine, from cold, it works fine, taking the temp to the middle position on the temp gauge, in about 3-6 min, as you say. If during the drive the coolant temperature drops , like when you go downhill for a long slope, the thermostat was never closing and for this reason the temp on the gauge was going dramatically down as 9.30 hours.
So I replaced the thermostat, in the spring, before the season and this summer it works perfectly.
I'm dying to find out what is happening in your engine! And I bet I'm not the only one!

 

[jonco]

.................... I bet I'm not the only one!

William Hill and Ladbrokes (bookmakers) have now got involved and just quoted following odds

2/1 - Cooling Water Pump
3/1 - Heater Matrix
8/1 - Thermostat Faulty
12/1- Missing thermostat

20/1 bar

Air Lock now withdrawn.

 

[upstream]

I received a call from the mechanic today. He said that he bled the radiator as well as flushed it and the heater matrix. He said that a load of rubbish came out but that now the Z will idle fine but every now and then the temp shoots up to around three quarters of max. In addition - the heater is the same as when I first took it to him. He wanted to change the thermostat. He felt confident that the water pump was ok.

After mulling over it for a few minutes I called him back and asked him to replace the water pump too (for some reason I just can't get the thought out of my head that this has something to do with it).

He'll get back to me once this has been done and he's had a chance to test it.

I'll keep you all informed but at this stage I'm definately with Jonco's bookmaker ;-)

 

[Zeti]

Now we will never know which of the 3, was the reason....dirt, thermostat, water pump....Unless he find clear damages.
But at least you will have your heating working and the car fixed!

 

[jonco]

Good call - if the pump does turn out to be the problem,then it would be good to salvage it and take some pics of any failure area. This could be of benefit to others who may encounter similar problems in the future. Also note what make it is.

 

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Well...
I had a call from the mechanic today. He said that he had removed the thermostat and that the housing was breaking down and that the thermostat was failing to open. He also said that he has kept it for me so that I can take it away when I collect the Z. He also said that this has cured the problem (despite not having changed the water pump which irks me somewhat because I wanted it changed).

Anyway - apparently having done all this the heater works fine however when you're stationary it does cool down "a little".

"A little cooler" I can live with but if when I pick it up tomorrow I find myself driving around feeling cold - I'm not going to be at all happy, especially as I had asked for (and it had been agreed) that the water pump would be changed. He's the expert though I guess.

Oh and also - apparently my rear window is leaking now