So tell me all you know about heat soak...

[oharab]

I had to open my mouth & brag about my new 540i!
Took it away for the weekend, stopped at Mac D's for some lunch on the way. Enjoyed(?) my bigmac then tried to set off. Turned the ignition, all the lights came on & nothing. Tried resetting the immobiliser and still nothing.

Eventually got in touch with the previous owner (Hi Trevor, if you're reading!;) ) and he told me about heat soak. He said it had been a problem with this car before & he'd replaced the starter motor because of heat soak.
I'd much rather not replace it again, so any ideas on why my car is prone to it and how I can solve it? If replacing the starter motor is the only way, is it a job I can do myself?

Spent a lot of time in a car park with my bonnet open this weekend, which cheered the wife up plenty, as you can imagine!

Any thoughts peeps?

Ben

[kyleN20]

my dads old chevelle would get this (1964 ss malibu) you have to either wait for it to cool down or jump the posts, this is how it was for his chevell and the problems sound similar but i dont want you to think this is somthing you have to do.

i replaced my started myself on a m30, mind you its a completly diffirent engine, but im only 20 and was 19 when i did it, if you do your own breaks and change your own oil you can get at one on a m30 easy enough, goold luck with the 8

[CharlesAFerg]

I so want a 540...

Don't people install thermostatically controlled electric fans in those to curb this problem? :D

[Omega]

Turned the ignition, all the lights came on & nothing. Tried resetting the immobiliser and still nothing.
Any thoughts peeps?
Ben

Welcome to the world of heat soak! I also have the same issue on my 2.5 M50. I imagine it's due to the solenoid arm sticking in the starter and can be fixed by removing the starter and greasing. Removing the starter on the M50 is a pita so I have another solution.

I carry a steering wheel lock that contains a steel bar. Place the bar on top of the starter solenoid (balanced off the injection rail) and turn the ignition key through the open drivers window with my left hand. As the starter clicks, hit the top of the bar with my right fist, which hits the solenoid which then starts. Obviously the instructions above are for a RHD UK/Aussie car.

If your car is a manual try rocking the car in gear. Mine's an auto and this rarely works.

The above "temporary" fix has been in use for about 8 months now!

[pingu]

I've had heat soak issues on both a 1991 525i (M50)manual (whick I no longer have) and my current car, a 1993 540i (M60) automatic.

On the 525 I had the starter motor replaced but this didn't help.

On the 540 I'm not going to have the starter motor replaced - as far as I can tell, the starter motor is fine. As an interim measure, I've had a bypass wire fitted which I can use to connect the +12V terminal of the solenoid directly to the battery (i.e. bypassing the ignition switch, non-park/neutral start inhibit relay and power distribution).

Whenever I get heat soak, I can start the 540 straight away by using the bypass wire. No need to give the starter motor a whack - so I reckon the starter motor is fine.

What I have noticed is that whenever I get the heat soak problem, there is only about 8.3V at the solenoid "+12V" terminal - this doesn't seem to be enough to engage the solenoid properly (although the dashboard lights do dim slightly). So there's a drop of about 3 or 4 volts somewhere between the battery and the solenoid +12V terminal.

The 3 to 4V drop isn't caused by the relay which is used to prevent starting in other than park or neutral.

I previously thought it was the ignition switch causing the 3 to 4V drop but I've had the ignition switch (and battery)replaced and I still get the heat soak problem, although now that the seasons are changing, the problem isn't as bad as in summer.

So I now reckon that the problem is a bad connection on the +12 power distribution. From the wiring diagrams, it seems that there is some +12V distribution going on inside the relay box under the rear of the bonnet, on the right hand side.

I'm going to have a look around/inside the fuse box for bad connections (hopefully a lose nut?) but if I can't find anything I'll probbaly just stick in some extra relays to bypass the problem (I'd rather fix the problem but sometimes it's a lot easier to fix the symptoms).

I think the diagnostic connector, maybe pin 10 or 11 (you'd better check), would allow you to connect the starter solenoid terminal straight to the battery (without needing to get a bypass wire installed) - make sure the ignition is on and that you're in park or neutral!

P.S. Another thing that makes me think that there is a bad power distribution connection is the OBD test #9. Test #9 normally pretty much agrees with multimeter but when I get the heak soak problem and turn the key to start, test #9 reads a full 1V lower than the multimeter. I reckon that the OBD is being partially being affected by poor +12V power distribution and so reads 1V less than the multimeter (which is connected to the +B jump start terminal and so isn't affect by e.g. the power distribution in the fuse box).

[Bill R.]

the heat shield the last time they changed the starter








Spent a lot of time in a car park with my bonnet open this weekend, which cheered the wife up plenty, as you can imagine!

Any thoughts peeps?

Ben[/quote]

[632 Regal]

mine is missing the heat shield but never had a problem like this, did it start after it cooled down?

[oharab]

It starts no problems after it's been left for a while.
Guess I'm gonna have to get the Bentley manual out & try & find the starter motor! The M60 looks a little different to my old M20!

No doubt I'll be back soon!

B.

[632 Regal]

to swap it out isnt difficult.

[Jay 535i]

When this happens to my 1986 Celica, the following trick works every time. No promises on your Bimmer:

1. Put the car in third gear, parking brake off.
2. Start to rock the car. It won't move much in gear, but an inch or two is enough to 'reset' the starter.
3. Try starting her.

As I said, works for me every time in the Toyota. The Bimmer is, um, slightly different, but it's worth a try, I figure.

[oharab]

Thanks for the thought Jay, but it's an auto box. It's also a rediculously heavy car, so shoving it even 2 inches would be "interesting"!

[Jon K]

Wow - can't say I've ever had this problem in my car and it gets HOT under the hood.

[632 Regal]

new starter time bro, might be able to get one used for cheap to make sure thats the issue before buying a new one.

Thanks for the thought Jay, but it's an auto box. It's also a rediculously heavy car, so shoving it even 2 inches would be "interesting"!

[Bill R.]

motor from the exhaust manifold. The m60 has an exhaust manifold right next to it.





Wow - can't say I've ever had this problem in my car and it gets HOT under the hood.

[632 Regal]

thus heat soak isnt the issue. Thanks Bill, now he should be looking for a bad selenoid or wire connection?
motor from the exhaust manifold. The m60 has an exhaust manifold right next to it.

[Bill R.]

Oharab's m60 does have an exhaust manifold right next to the starter but the m50's don't.




thus heat soak isnt the issue. Thanks Bill, now he should be looking for a bad selenoid or wire connection?

[dternst]

Can someone explain to me what exactly is heat soak?

[DaveVoorhis]

Heat soak is where you turn off the engine and heat -- previously kept in check by flowing air and the cooling system -- emanates from the engine and toasts nearby parts, like the starter solenoid and starter motor.

A typical symptom is a problem that only manifests after the vehicle has been fully warmed up, stopped, and allowed to "cool" for fifteen minutes or so. In fact, the engine is cooling by losing heat energy to the surrounding parts. This can cause a marginal component to act up.

Heat soak also refers to the effect where the engine temperature -- as indicated on the gauge -- will rise after a hot engine has been stopped for a bit. It should drop to normal quickly after the engine is started.

[gtopaul]

When I used to have this problem on my old GTO out in Arizona I used to carry around a empty anti freeze bottle full of water. The Pontiac had the original jack stand which was hollow and I would set the end of the jack down onto the starter and pour water into it. A gallon of water over the starter later, it never failed to start. You might try the water trick just to eliminate that it isn't really a starter heat soak problem. Just carry a section of hose or something to guide the water onto the starter.

Paul

[Omega]

motor from the exhaust manifold. The m60 has an exhaust manifold right next to it.


thus heat soak isnt the issue.

Not true Jeff. My old e34 had the M50 engine and suffered with heat soak on the starter for over 12 months. In warm weather it would occasionally stick, requiring the aid of a prodding device (thwack from a bit of 2x2) to unstick. Gradually it got to the stage that it would stick about 90% of the time once the engine was warm regardless of outside temp.

Sometimes the starter could be freed just by dropping the shifter into neutral and back to Park (takes the pressure off the auto box/flex plate momentarily - I never use the handbrake so the box was in effect holding the car static) or by leaning against the B-pillar and rocking once. It never "proper" stuck to the point I had to beat crap out of the starter.

As it was so easy to free up I suspect that the solenoid was a bit sticky and that something was expanding just enough to catch the pinion when the starter got warm . I could probably have removed the starter, cleaned and reinstalled it however everytime I looked at it, it looked like a real p.i.t.a. to remove without unbolting tons of other stuff (like the intake) so I learnt to live with it to the point where I lifted the hood and hit the starter before getting into the car..... Force of habit.

Didn't solve the problem and to my knowledge it still does it, but it's not my problem any more!



You might try the water trick just to eliminate that it isn't really a starter heat soak problem

Interesting approach:D but as the starter circuit probably carries the peak current load of the whole car and baring in mind just how much sensitive electrical gear there is in the average BMW I personally wont be throwing water all over the starter.

.

[gtopaul]

Interesting approach:D but as the starter circuit probably carries the peak current load of the whole car and baring in mind just how much sensitive electrical gear there is in the average BMW I personally wont be throwing water all over the starter.

.

Well you do it with the engine off and the starter is down where it's exposed to the elements anyway so it's not like pouring water over it is something it hasn't seen before. ;) If that was a problem it would be in some sort of sealed box. You know BMW engineering.

Paul

[silver-e34]

i had the same problem on my 525i after several starter replacements and cleaning several ground points and extensive tests realized it was the aluminum 80a main fuse on the strut tower was cracked but i couldnt tell because it was under the bolt that holds it in place,i kept thinking it was the starter because it only happened after the car would sit for about 15 min on a hot day after warming up and every once in a while it would start if i tapped it with a hammer,i replaced the fuse and my problems were over

[oharab]

Got it fixed a couple of months back, thought I'd better update you all and maybe help someone else with this problem.
Put in a new starter motor in the end. Went with a brand new OEM bit, £395+fitting. Looks like the one replaced by the previous owner was a reconditioned unit, so hopefully this new one will last longer!
Car starts 1st time, every time now, though sometimes it seems to take a second or two to catch, but not very often.
All I need to do now is get some sub-frame bushes & some steering bushes replaced and the car will be ready for it's next fault!

These cars really are like the best women: Fast, easy to ride, but expensive in the long run :)

B.

[bigtisas]

Thanks for the explanation DaveVoorhis. I wonder if newer BMWs still have heat soak problem. Why don't BMW use thermostat-controlled electric fan?