coolant change by intuition. what might have gone wrong?

Post Tue Oct 04, 2005 2:11 pm

hi there,

think this might have caused some engine damage? what might go wrong with this?

the coolant had drained trought the perforated hose at the bottom of the radiator(just after i parked it, didn't drain during the drive).

the next day i replaced the hose, and with the engine off and cold
i filled the coolant vessel to the sign and started the engine. the engine imediatley revved up to 2.000 rpms, and the coolant wasn't flowing. i checked the temp gauge and after 5 mins it just nudged 1 mm on the scale.
but looking at the engine running it was obviously the engine was pretty hot, suddenly the coolant started flowing and let the vessel empty again, quickly i filled it up again, and looking at the temp gauge i seen the needle rise fast to the third line, not into the red zone yet.
the vessel was emptying rapidly as the cooland made its circuit, and i kept filling it with coolant, but the coolant that was already in was sizzling hot. it was obviously the sensor didn't detect the real engine temperature until the coolant reached it. and just after that the engine sarted to rev down, at it's normal idle.
and then, JUST THEN, i turned on the heater at full, and the needle quckly went down to the medium and below heating temp.
turned out the engine.
now filled it up, and bled the air out, seems to be in optimum, now, it doesn't overheat.
but i feel a bit diffrent the idle, seems a bit rougher(maybe placebo efect?)
what kind of damage might it sustained there after this or IF it sustained any damage?

thanks!

Post Tue Oct 04, 2005 2:39 pm

might of created an air bubble in the system in the head and a hot spot .
i wouldnt of said anything is hurt thou as u didnt drive it .

did you squeeze water hoses to try and move air out at all ?

Post Tue Oct 04, 2005 3:16 pm

no, didn't squeeze hoses, just bled through the bleed screw, and kept watching the temp gauge. it seems to work fine now, no overheat for half an hour of idling and reving.

Post Tue Oct 04, 2005 4:29 pm

You need to have the heater on full blast when refilling to ensure system is full otherwise you'll create further air locks. A tip for ensuring that the system is fully bled (bleed screws on on the thermostat housing aren't always the best) is to release the clear reservoire from the engine compartment wall and with the cap off, raise it as high as it will go, while you are filling it (careful not to burn yourself!).
As you have overheated it, it would be best to check for oil in the coolant (mayo) after a few miles and conversly water droplets in the oil. Hopefully it should be OK tho. Hope this helps.

Post Tue Oct 04, 2005 4:50 pm

the reason for the delay in the coolant circulating when you filled it from cold was probably due to the thermostat, if it is dodgy then it is worth changing it for the sake of Ãƒ”šÃ‚£20.

You could have had an air lock too as mentioned and always fill a car with the heater set to full temp

Dodgy tickover etc could be caused by the temperature sensor which is linked to the ECU, there are 2 sensors, 1 for the gauge and 1 for the ECU, both are just near the thermostat housing on the M20, if your car has cooked itself at one point then the temp sensor to the ecu sends a signal and it tells the ECU to adjust the fuel mixture, but I think it stays that way so the car thinks it needs to overfuel or underfuel (can't remember which one)

Prob best to wait for one of the heros like Brianmoooore to arrive and correct my advice

Post Tue Oct 04, 2005 11:44 pm

This sounds like a very good attemt to crack a cylinder head. Hopefully unsuccessfull. Sounds like you had airlocks everywhere.
Follow the advice given above to fill the cooling system - helps to have the front of the car hifger than the back as well. It can take a week to get all the air out completely.
You don't say which engine you have, but if its a 325 M20, you've really been pushing your luck!

Post Tue Oct 04, 2005 11:48 pm

if its an m42 then your even luckier not to

Post Wed Oct 05, 2005 10:24 am

thanks a lot for your advice gentlemen, it was warmly welcome!!
the engine is m20 320i.
i filled it in the end nad started the engine with the heater on full. and bled through the screw with the front higher than the back. seems to be ok now.
surely now, i know the correct way to replace the coolant

hope the engine is dammage free after my first poor atempt.

Post Wed Oct 05, 2005 10:28 am

320 head is a lot more resilient to this sort of treatment than the 325, so hopefully all is fine.

Post Wed Oct 05, 2005 12:34 pm

Dodgy tickover etc could be caused by the temperature sensor which is linked to the ECU, there are 2 sensors, 1 for the gauge and 1 for the ECU, both are just near the thermostat housing on the M20, if your car has cooked itself at one point then the temp sensor to the ecu sends a signal and it tells the ECU to adjust the fuel mixture, but I think it stays that way so the car thinks it needs to overfuel or underfuel (can't remember which one)

hi people, fairly new to the zone, may have to start a new thread regarding my problem but what are the symptoms/effects of the above sensors being faulty, my 320i tourings mixture is knackered(i.e. 4000ppm HC on analyzer) but seems to run a lot better when cold albeit terribly....
throttle response is also very poor and sometimes even backfires.

dont mean to hijack

Post Wed Oct 05, 2005 4:28 pm

Welcome to the Zone! and E30 madness. I suggest you start a new thread as you say. You should get lots of help with this one, rough running seems to be fairly common but we won't find it under an coolant thread!

Post Thu Oct 06, 2005 5:11 pm

thanks, will do, when i get 10 mins spare that is!