318i overheating? *sussed waterpump*

[aze30]

i went for a short drive to the shops yesterday late evening.
started the car it ran fine warmed up idled fine etc
whilst driving the car i had warm air and the car got upto temperature fine.
now on my way back i was a little fruity with the throttle not thrashing it but just making progress two streets before i got home i noticed the heater blowing cold air.
when i stopped at my house i saw the temp needle on red, i immediately switched the car off and opened the bonnet to be greeted by steam bellowing from the radiator cap area.
the radiator pipe seemed hard and pressurised.
come morning ive put in around 1.5 litres of water in and drove to work (less than a mile) and the car got to the three quarter mark on temp guage.
tried bleeding it this evening from ratiator bleed screw next to the cap with no joy temp goes up and no hot air in car.

prior to this the car has never given any trouble.
i regularly checked oil and coolant levels these were fine on monday last week.
no oil or water mixing
no missfires
car has 50k miles genuine with full history and regular oil and coolant changes.
engine is a 1.8i m40
im hoping its not the gasket...

any ideas guys?
help would be much appreciated
thanks
azzy

[Brianmoooore]

Bleed the heater circuit by filling the coolant bottle to the brim, pulling off the top heater pipe on the stub pipe on the engine bulkhead, and then refitting it with coolant flowing slowly from both the pipe and the stub, then try driving the car and note exactly what happens.
Unless the overheating was caused by a simple coolant leak somewhere, a failed head gasket is one of the better options you can hope for.

[aze30]

thanks brian i will try that and report back tomorrow

[Andyboy]

Sounds like the water pump impellers have fallen off. Unlike the M43 (same block and same head gasket), the old M40 engine rarely blows the head gasket. It can also be a failed thermostat that's decided to stick shut.

Start from scratch - whip the top hose from the radiator and slowly add water (don't waste anti freeze at this point) until the level is up to max in the header tank, Refit the cap tightly and continue adding water until the hose is full. Fire it up with the bleed screw undone, and hold it at 2000 rpm with the heater set to hot. You should be getting warm air from the vents within 2 minutes. If not, remove the thermostat and check it by heating it up in a pan - it should open up just before it gets to boiling point. If you want to fit a new one anyway, refit the stat with the centre removed and see if that helps. If the water pump looks old, it's worth fitting a new one anyway but they can really take some shifting after a few years and often require removing with a hammer and small chisel/big screwdriver in sections. You can try the 10mm bolts trick (the pump body has two threaded holes either side - the 10mm bolts are wound in to ease the pump out) but 9/10 the ears just break off the pump.

[aze30]

cool andyboy thanks for that bit of info i will try that tomorrow.

today i tried brians method of bleeding...and yes it did seem to bleed up fine as in i kept the hosepipe in the radiator and removed the top stub hose at the bulkhead....i made sure to keep it there untill all water was flowing from both ends before fitting them back up carefully.

i started the car up and let it idle for a short few minutes with the radiator cap back on...around 6 minutes of running the temp guage went to three quarters, still no hot air in the cabin.
i switched engine off and had a feel of the radiator pipes....the shorter radiator pipe from the thermostat housing to the rad was cold...the other pipe from rad to the engine was hot and felt like there was some pressure but not really hard.

at this point im assuming the stat is stuck....what you guys think? i will be replacing this tomorrow and see if that works...im keeping my fingers crossed.....

Azzy

[Brianmoooore]

Heater should still work with a stuck 'stat, so it looks like it might be the pump.

[aze30]

thanks brian...should the heater work even if the headgasket has gone?

[Brianmoooore]

The heater will work as long as the pump is pushing coolant through it, and as long as it isn't air locked. Once fully bled, the only way an airlock can reform is by letting the coolant level get so low that the pump pushes in air, or by combustion gasses getting into the water jacket via a cracked head or blown head gasket.
You haven't let the coolant level get that low this time, so it's either airlocked (unlikely, if the heater never got hot - it usually takes time for an airlock to form), or the coolant isn't being pumped.

[aze30]

thanks Brian...charged with more info i will try tackling it again tomorrow.... i will try getting that pump off for an inspection.

Azzy

[Brianmoooore]

Try to get the whole pump turning in its housing after you've removed the bolts and applying plenty of penetrating oil, before you try to get it out. That way the ears that you screw bolts into to extract it might just survive.

[aze30]

Thanks Brian and Andyboy for your help guys...much appreciated!

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right i found that the waterpump was the fault here.
i managed to get it out in 20 mins flat so was well chuffed there as i was dreading it to be a PITA.
i opened the four 10mm bolts holding the pump in place and used a hammer to tap the waterpump housing from side to side a few times till the pump had some free movement, once i had that movement i placed two bolts into those 'ears' you mentioned and gently tightened them...then gradually giving them a few turns then a few taps on the housing then a few turns on the bolts and back to tapping the housing untill it was free.
worked a treat!
will put it all together again tomorrow with a new pump and will do an oil change at the same time aswell as fresh plugs and filters.

Azzy

[Brianmoooore]

Removed like a true, natural mechanic! It isn't often you see a second hand pump on the bench with both 'ears' still intact.
Have fish around for any missing plastic bits that might be inside the block, and try to get a replacement pump with a metal rotor.

[aze30]

haha true mechanic?...i wish! ...im a novice that just likes to tinker with old cars as a hobby lol
i have no mechanical workshop experience....just personal willingness to open and fix things haha.
i did have a good smooch in the pump housing of the block and got out all the bits of plastic i could find....the new pump from ecp is the only one available being a circoli pump..i will check it to see if it has a metal impeller when it arrives today.

Azzy

[Brianmoooore]

Circoli is a good make, and the M20 version, at least, has a sheet metal impeller.

[DanThe]

I prefer the pressed steel impeller pumps, much less weight hanging off the back of the bearing

[aze30]

This pump has a cast impeller and it is as dan says nice and light.
parts are here so will be fitting it all up after work tonight

[aze30]

Fixted it!
bled up fine and ran smooth like a dream ...left it running idle for 20 mins as i packed away my tools temp was a tick under half.

[Brianmoooore]

And the heater works, I take it.

[aze30]

Yup blows nice and hot kept me warm on the way home
thanks guys!