I need my head analysed!

[PeteE30Tourer]

Got my 325 back today after it's head transplant. I took a good look at the old head to see if i could see any damage that might have caused the water leak into the oil. See pics below:

Complete head:


Question 1 - why would some of the valves look a lot cleaner than the others? Look at the inlet valves on cylinders 1, 3 & 6 (1 is on the left) - they're totally black compared to the others.

I think this may have been my problem though:




Two nice little chunks out of the casting in the water chamber adjacent to cylinder 6. Seems a lot more drastic than i'd imagined, but i can see one of them is very close to the edge of the cylinder.

Finally, what's going on here?


Strange scorch-like markings on No.5 cylinder inlet valve.

Any opinions or advice welcomed.

[TOURINGDADDY]

that to mate looks like your valves are burnt out, time 4 overhaul but befour u spend too much wedge get the head crack/pressure tested

[PeteE30Tourer]

I've already put a replacement head on the car, but you have reminded me of another question i meant to ask. Is it worth having this old head repaired (i.e. welded), skimmed, pressure tested then putting it up for sale? Sounds like i may end up throwing more money at it than i'd get back.

[TOURINGDADDY]

def worth gettin crack tested, never know who or when it may b needed

[E30Adam]

That's the source of your water leak mate. M20 heads suffer badly from the water jackets corroding in this area.

[PeteE30Tourer]

I figured this was probably the case - looks extremely close to the inside edge of the gasket.

Worth repairing for sale you reckon?

[PeteE30Tourer]

that to mate looks like your valves are burnt out

What makes this happen? I thought it was something to do with pre-ignition from my memory of older cars, but in theory this shouldn't happen on modern ECU controlled engines. Strange also that it's only apparent on one cylinder.

[Martinaston]

The chunks missing out of the water channel at the rear was rust and just a matter of time before that went, so i'd say make sure you change the coolent more regularly with the new head.
However you stated that the reason you changed it was because of water in the oil and the only way you can tell for sure is to have a look at the old gasket and trace the water marks on it. You may be able to see it on the face of the head but if it was below the gasket it would show on the block face.
As for that dodgy valve are you sure the mechanic has not poked it with something ?
I thought burnt valves refered to the valve seat but i'm not sure.

[E30Adam]

The chunks missing out of the water channel at the rear was rust and just a matter of time before that went, so i'd say make sure you change the coolent more regularly with the new head.
However you stated that the reason you changed it was because of water in the oil and the only way you can tell for sure is to have a look at the old gasket and trace the water marks on it. You may be able to see it on the face of the head but if it was below the gasket it would show on the block face.
As for that dodgy valve are you sure the mechanic has not poked it with something ?
I thought burnt valves refered to the valve seat but i'm not sure.

Mate... alloy doesn't rust, the water jackets break up because of corrosion to the metal over time. Alloy is quite a weak metal and will break up over time. Coupled with the fact that it's a bad design with this section of the head being so narrow leads to this problem.

[Brianmoooore]

The damage shown would put water down the exhaust, not water in the oil, and if it had been leaking here, the relevant cylinder should have been "steam cleaned".
I think this damage might be a red herring.
Turn your head over, and carefully examine the bottom of the cam bearings, especially no 3. If you can see a grey line running across one, this is a crack.

[Simon]

The damage shown would put water down the exhaust, not water in the oil, and if it had been leaking here, the relevant cylinder should have been "steam cleaned".
I think this damage might be a red herring.
Turn your head over, and carefully examine the bottom of the cam bearings, especially no 3. If you can see a grey line running across one, this is a crack.

IIRC the problem Pete had was coolant loss, but not any mixing problems, he said he was suffering from excessive steaming from the exhaust too, looking at the pic, that must have been the problem, it's very very close to the chamber.

[Brianmoooore]

i could see any damage that might have caused the water leak into the oil. .

[Simon]

i could see any damage that might have caused the water leak into the oil. .

Just had a quick read, and his initial problem was just coolant loss, but eventually he had mixing problems.

http://www.e30zone.co.uk/modules.php?na ... ht=#105589

[Martinaston]

E30 Adam
You appear to be contradicting yourself in that statment

I'm pretty sure aluminium does rust but as it doesn't contain iron the rust is not red it just turns to a fine white/grey dust.

Thats what happens to your wheels when they loose there luster.

[Richy325iTouring]

aluminiumoxidisesit doestnt rust
simular thing though

[Simon]

aluminiumoxidisesit doestnt rust
simular thing though

Says Richy with a dodgy spacebar

[Richy325iTouring]

bloody thing
its getting on my tits now drrrrr



Keyboard gets thrown though the window real soon

[Martinaston]

I'll have to get mine gold plated then

[Martinaston]

Or made of solid gold.
Then i'd be happy to pay 400+ for one

[Brianmoooore]

Doen't corrode if it's serviced properly with the correct coolant.

[PeteE30Tourer]

The original problem was just coolant loss, rough running from cold and white smoke from the exhaust - no water in the oil. Then it got worse a couple of weeks after i blew a coolant hose off as i began to find traces of mayonaise on the oil filler cap. That's when i took it off the road straight away.

It is odd though that if this is where water was leaking into the cylinder that it wasn't steam cleaned.

I guess the moral of the story is though to use good quality antifreeze and keep it topped up all the time to prevent any such corrosion.

[Martinaston]

If it blew a hose then i suspect it was the combustion gases forcing there way into the coolent and then when the engine was off the coolent was seeping into the chamber and causing the rough running.

How old is the car (well engine) ?

[PeteE30Tourer]

If it blew a hose then i suspect it was the combustion gases forcing there way into the coolent and then when the engine was off the coolent was seeping into the chamber and causing the rough running.

This was the theory i was working on before i had the hose blow off. The rough running from cold was due to water seeping into one of the cylinders under pressure when the engine was off, then shortly after it had started up, i'd notice loads of white clouds behind me as it was all boiled off through the exhaust. I think the hose blowing just made this situation worse, but it was still another two weeks after this that i first started noticing water in the oil - up to then it was fine.

How old is the car (well engine) ?

Car is 1989 with 140kmiles on the clock.

[Martinaston]

Now it's re-built you'll have to listen out for big end bearing wear as the water may have replaced the oil and burnt them, But if you stopped driving it soon enough it sshould be ok.

140k Oh dear i've just done 137k

[Adammcf]

LOL! Mine just went porous at 116k.

[Simon]

And mine went at 108k...we're getting lower

[k130]

Mines on 127K...

Anyone got a spare head for a 323i ????

[e30_Turbo]

149,532..... better keep an eye on mine then

[320Touring]

Mines on 127K...

Anyone got a spare head for a 323i ????

you'll be fine mate-the '731' head found on the 320i and 323i is of a slightly different design to the one on the 325i

It is a 'flathead' so the water channels are not as likely to split (as there is more alloy round abou them

[Widge]

Mine's on 176,000 and still going strong!
Stop scare mongering 320touring - just trying to big up the 731 club's only merit

[320Touring]

Mine's on 176,000 and still going strong!
Stop scare mongering 320touring - just trying to big up the 731 club's only merit

no scaremongering mate!!!!! the 325 head is ok if gets coolent done properly and is well looked after