coolant light off, then after all while it comes on?

[sibzilla]

Hi,

I'm a little paranoid and confused. Does the coolant light have more than one sensor that can get it to turn on? (I have a 325 estate, J reg/m20 engine)

I've just done a head gasket change and I'm quite worried Ive screwed it up (even though I thought it was fairly easy to do - my confidence may have been my curse) because now the coolant level sensor seemed to come on after then engine warmed up even though the level was topped up, so I turned off, remove the key, and then put it back in again and the light was off once again???

I didnt look into it anymore, just went home feeling defeated (car is on a friends drive) and expected to find a post with a similar problem (but no?!)

also, my thermostat housing was corroded to buggery so I got another from a breakers and I think it has a fekkd temp sensor as the car doesn't know its hot. whats the other sensor in there? or would that indicate a dodgy stat?

...fingers crossed - any advice would be great!

*bows to the greater knowledge of e30zone*

[E30BeemerLad]

there are 2 sensors, a blue one which i think is to the ecu and a brown one for temp gauge, but i'm not 100% i have those the right way around.

the coolant level sensor on the expansion tank could be faulty. Did you disturb the expansion tank, such as having it stood on it's end?

Mine had the light on the check panel after i did my camblet & had the rad out. A quick bang on top of the expansion tank and it went off. Sensor had just stuck in the wrong position

[Simon]

there are 2 sensors, a blue one which i think is to the ecu and a brown one for temp gauge, but i'm not 100% i have those the right way around.

the coolant level sensor on the expansion tank could be faulty. Did you disturb the expansion tank, such as having it stood on it's end?

Mine had the light on the check panel after i did my camblet & had the rad out. A quick bang on top of the expansion tank and it went off. Sensor had just stuck in the wrong position

Sensors are correct...


You say the check LED came on for coolant level yes?

Sounds to me that there was an airlock (very common and a total pain on the M20!) that cleared itself, and then this was shown in the coolant level, get the car parked facing uphill, unscrew the bleed screw again, let any air out, top up when cool, and ru the car upto temp again.

Also, fingers crossed this isn't the problem, but keep an eye out for any mixing of water and oil, just incase the gasket hasn't sealed properly.

[sibzilla]

ah! e30beemerlad I read your cambelt posts from start to finish!

thanks for that fella

I had the expansion tank out completely - it had a little mayo in so I wanted rid of it and flushed it through.

The thing is, the coolant sensor appeared to be working as it wasn't lit at first (while engine was cold at first start) it was only once it got up to temp that it came on... I looked through the window to see if the temp guage has moved from the cold position as the water had started to steam and I was waiting for the engine to drink it as the stat opened... anyway, nothing was showing up so I kept the engine running while I fiddled with the bonnet bolts and then after I had that done I looked in to see the temp needle was still showing as cold and the coolant light was on, I topped up the tank with more coolant, and the light went out for a short while but I checked it soon after and it was on again (at which point I nearly started crying - the grease, the sweat and the bleeding is nothing to me, but failure... oh god please no... that and the potential loss of an enjoyable RWD car)

also there is some kind of electronic choke device (auxhilary air control valve? has bosch written on it) running to the throttle body which buzzed and seemed to cause some hunting while plugged in, but unplugged ran smoother (although with a higher idle)

I guess I better start reading some posts!

thanks for your reply mate, your posts are all very encouraging I must say ;)

[sibzilla]

air lock sounds plausable (or even poorly sealed HG) so I'll try your suggestions Simon, I did look for bubbles in the tank and didnt see. I'll keep my eyes open for oil/water mixing - where would you say I'll see that happen first? on the dipstick, under the oil cap or floating at the top of the water?

the car did appear to take a lot of water (but then it spat a fair old amount out too)

whats water capacity anyway?

[Brianmoooore]

The Bosch thing is the idle control valve. It's a stepper motor air valve controlled by the ECU, which is plumbed in parallel with the throttle butterfly. i.e. it's a second, smaller throttle which the ECU uses to control idle speed. The buzzing is normal.
Can take up to a week to get all the air out of a M20, and for the coolant level to finally settle down. Once the coolant light is on, it stays on untill the ignition is turned off, even if the coolant level is corrected, so the slightest blip in the coolant level,sensor output will turn the light on.
For future reference, when you've partly emptied the cooling system on an E30, make sure the heater is turned to full hot when you fill it again, turn the fan on and make sure that warm air starts to come from the heater after half a minute or so. If it doesn't you have an airlock, and are risking cracking the head.

[sibzilla]

awesome - thanks Brianmoooore.

fingers crossed for me then

do you think the stepper motor causing hunting would suggest its broken? or perhaps it because the car's been chipped? (accrding to the guy who sold it to me, it has no mods but a panel filter and chip)

I should really start searching I guess...

(very impressed with this forum btw, thanks very much guys!)

[Brianmoooore]

A clean out of the ICV with carb. cleaner wouldn't go amiss, then check the throttle position switch is set correctly and is working electrically.

[sibzilla]

cheers, i noticed the pipes running to the ICV were split and allowing unmetered air in so I fixed this with a fair old bit of epoxy resin. I'm wondering if the previous owner might have set the idle with the screw on the TPS - presumably I want to hear it click (which isn't something I noticed before, but I'll check tomorrow am) so I know its in the correct place... if it clicks is it all good or is there still some room for adjustment?

I looked for idle speed adjustment and didnt find anyway to set the idle speed, just warning not to bugger about with said screw too much. is there a way..?

oh, btw - I gave the ICV a good clean with WD40 for good measure, it doesn't appear to be broken in hindsight, its far more likely I still have a vac leak somewhere I havent noticed yet.

[Brianmoooore]

Ypu now need to spray carb cleaner through the ICV to remove the WD40! WD40 is good stuff and has many uses, but cleaning electrical stuff isn't amongst them.
Air leaks are a distinct possibility. If the convoluted air hose is split, then it is perished. A new one is only around £10.
If the phantom twiddler has been at work, then everything will have to be set up again from scratch

[sibzilla]

WD40 and a lighter for the phantom twiddler it is then

thanks for all the advice fella, really - its very much appreciated!

[sibzilla]

For anyone who searches and finds this thread: the coolant sensor came on because of an airlock freeing itslelf up and as pointed out, once the light is on - it stays on until the ign. is turned off. I fixed this by bleeding from the 'stat and then by diconnecting the top heater hose and allowing air out there.

Oh, and WD40 didn't do the ICV any favours - it was loads better after some STP carb cleaner was sprayed in.