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blown head gasket

731 views 17 replies 4 participants last post by  Gary 
#1 ·
arrgghhh my cars gone a bit Tim P:D

i blew the head gasket on the M3 today, luckly right by the 300 yard sign for the entrance to the new services!

Anyway my question is i realised it went cos i went to accelerate and it didn't (not even 1mph) then i noticed the engine temp was flashing so i came off the accelerator and there was this 'squeeling' noise, so i put my foot on the pedal again and it went away.
Came of the pedal again and it returned, does anyone know what it is? it sounded like it was coming from the drivers side of the engine bay

I can hazzard a guess at the water pump as there was only about 2 or 3 litres of coolant left in it, if it is the pump would it need replacing?

any ideas?
 
#2 ·
JamesG said:
arrgghhh my cars gone a bit Tim P:D

i blew the head gasket on the M3 today, luckly right by the 300 yard sign for the entrance to the new services!

Anyway my question is i realised it went cos i went to accelerate and it didn't (not even 1mph) then i noticed the engine temp was flashing so i came off the accelerator and there was this 'squeeling' noise, so i put my foot on the pedal again and it went away.
Came of the pedal again and it returned, does anyone know what it is? it sounded like it was coming from the drivers side of the engine bay

I can hazzard a guess at the water pump as there was only about 2 or 3 litres of coolant left in the system so it was probably running dry, if it is the pump would it need replacing?

any ideas?
 
#6 · (Edited)
Its done 99k and the last cam belt change was at 70k...

it really is puzzling me as the noise went away when i put my foot back on the accelerator and came back when i lifted off...

I took the exhaust manifold off this morning before work and about half a litre of water pissed out of it!

i had a look down the spark plug holes and no 2 has a nice little puddle sitting on the piston...

The car has always maintained a good running temp, i've been sat in traffic for 45 mins before and it didn't go over 1 green and 2 yellow bars.... normally it sits at 1 green and 1 yellow.
 
#7 ·
change it anyway then when the head comes off - it's way past it's best - even if it's ok another cambelt change might kill it.

judging by the state of the engine, I think it's best to change the gasket, check everything, and see what gives when you start it up again - working out what made the noise is going to be impossible now...
 
#8 ·
Cheers for the help Gary, I've been into work and kicked off at our fleet manager as i was on company business when this happened and should have had a company car but was told none were available, and all of a sudden he's found a car....

a nice little BMW coupe! bonus i can have it for 2 weeks so i've decided to go the whole hog, strip the head e.t.c full rebuild.

I was always gonna change the gasket as it is obvious its gone i was just worried about what the noise could be but like you say it's to late to find out now....

how much are water pumps??

any advice on things to watch out for/things i can do to improve the engine when i rebuild it - im gonna do the breather mod, is there anything else i could do while it's all in bits, short of lairy cams e.t.c.....
 
#9 ·
whoooaaa.. you don't wanna be asking me that ;) - and definitely under no circumstances ask for Animals advice...:eek:

boils down to 'how much (time/money) you got' ?

first up, get a GM water pump @ about 50 quid exchange - avoid pattern pumps.

check the BE journals with the crank still in - if they're not scored or oval, assume the mains are ok and leave em be. Do replace the BE shells though, and go for lead copper - but if you don't mind the extra work, have the crank out and get it balanced, but not lightened, replace main shells if you want to.

replace the crank woodruff key - they can shear off! - not good..

check the oil pump pressure relief bore and plunger for scoring - polish any out as best you can - if it's bad, new plunger and/or pump casting - and replace the two oil pump gears anyway - belt and braces would be a nylon relief valve plunger from SBD.

lightened and balanced flywheels a good move.

new rings, obviously - and if the block is worn too much, a rebore - then you're into new piston territory and Omegas probably work out cheaper than new Mahles - then of course you have the option of bigger pockets and wilder cams - even if the block is ok, you can still get bigger pockets put it your existing pistons, and a medium-wild cam profile to match - if you've got the time or inclination, get the conrods crack testing and balanced if you're thinking of serious tuning. Either way, pay attention to the rehone on the block and take your time - you only want to be messing with the bottom end once. Consider ARP rod bolts for a higher rev limit, too - if you got the cash, steel rods are worth they weight in 'peace of mind', and the ability to take anything you can throw at them..

if you rebuild the head, then you may as well strip it and gasflow etc.. - replace guides if needed - new stem seals, redress valves etc etc. and make sure you have it skimmed before it goes back on - think ahead to the cam profile you want and uprate bits where needed.

do the breather mod on the inner cam cover plate.

get the injectors cleaned while the engines in bits.

ditch the old bosch brain..add throttle bod...uh oh - here we go.. now you see why you shouldn't ask people like me...? ;)
 
#10 ·
arrghhhhhhhhhh:eek: :eek:

can i have that in english please...:p

I'm don't wanna do the block itself - i've never done one and i don't really have the time to go that far, but i will check it all and take it from there

I was thinking headwork, flywheel, getting the injectors cleaned, water pump, checking the oil pump e.t.c....

I'd love to go the whole balanced bottom-end, throttlebodies route, but if i did decide to, i'd probably buy a whole engine and work on it so i can use the car in the interim

skimming the head and lightening the flywheel is nice and easy as my dad has an aircraft engineering company so i can get them to do all that work:D

how much should i take of the fly? like i said i don't want to go to mental...

cheers for the advice.....
 
#11 ·
if you've the early type, then you could maybe shave it down to 6kgs or so - the later types are a lot heavier and would need a lot more taking off to get down that far - work on about 5.5kgs as the lightest you want to go with a cast one.

otherwise your list of things is about right - like you say once you start getting into it you end up wanting to do a lot more... :)
 
#12 ·
first up, get a GM water pump @ about 50 quid exchange - avoid pattern pumps.
Don't want to run the risk of starting a fight here, but........

The original GM pump was made by Quinten Hazel (QH) and the QH pumps on sale at Halfords et. al. are identical down to the flashing marks. Only difference is no GM marks, even the part numbers are the same but for the date coding.
 
#13 ·
last question i promise!!!

As im gonna get the injectors ultra sonically cleaned im gonna need to take them out, but how can i de-pressurise the system, as i can't start the engine and remove the fuel relay fuse as the engine doesnt run!

Gary, i know what you mean about wanting to do more..
initially it was gonna be a strait forward gasket change then i thought "well while the head off i could..." and it went from there:D

what does the standard fly weigh?? i have an early type so i'll probably have it machined down to about 6kgs...
 
#15 ·
fair point Trevor - but I don't really class that as a pattern part, per se - an exception in this case then. The ones I've seen are awful - i.e Partco etc..

depressurise system by catching excess petrol in your eyes - works a treat :) - seriously don't worry, just unbolt with a big rag around it - normally you'd just leave the engine running and unplug the fuel pump.

the early flys are about 7kgs I think..
 
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