Engine Mayo :(

[knapmann]

Having a bad day, when changing the oil on my new build engine I found mayo under the rocker cover. The actual head itself looks mayo free but the engine IS using coolant. I rebuilt the engine from a runner, so it was OK before, its only done about 500 miles. I had the head and block skimmed when rebuilding and used a new BMW head gasket. I just finished removing the cylinder head hoping to find an obvious cause but the gasket looks fine and there are no obvious traces of leaks, the head looks fine too, no obvious cracks, the engine hasnt overheated to my knowledge. All the cylinders look the same colour as well. Basically I have no idea where the leak is has come from. Any ideas?

TIA

[steve_k]

mayo can happen after short trips where the engine doesn't get up to temp,

as for the coolant leak, is the pas side carpet damp/wet??

[knapmann]

mayo can happen after short trips where the engine doesn't get up to temp,

as for the coolant leak, is the pas side carpet damp/wet??

There are no signs of coolant leaking outside or inside the car, not even a drip on the floor but I am adding coolant semi-often. As the engine is new I wondered if the level was dropping due to air pockets in the engine being filled when running. I don't do short journeys, my previous drive to this was 45 mins thrash around, high revs and full temp throughout. That was a week ago. today I just idled the engine to temperature to do an oil change, I'm fairly sure the mayo hasn't come from 15 mins of idling it will have been there already, that plus the coolant loss equals some kind of leak, I wouldnt mind if the source was apparent, but I dont have a clue where its coming from. I could change my head gasket and nothing could change.

[bmw9818]

sniff test/ compression tester kit if you can get access to one,

[knapmann]

sniff test/ compression tester kit if you can get access to one,

When I built the engine about 2 months ago I tested compression at 170-180 on all cylinders, it may have changed for some reason but all seemed ok then.

[maxfield]

Did you get the head pressure tested and skimmed?

[knapmann]

Did you get the head pressure tested and skimmed?

It was skimmed but not pressure tested as it was from a good runner already so I didnt see the need.

[Brianmoooore]

Get the engine up to temp. and the cooling system under pressure, then let the engine idle with the rocker cover off. Look carefully at the area of the head under the cam near the rear two cam bearings for little beads of water emerging, scooting across the surface, and disappearing down an oil return hole.

[aimlessrock]

hope you head is not cracked..is she a B20 or B25?

[knapmann]

Get the engine up to temp. and the cooling system under pressure, then let the engine idle with the rocker cover off. Look carefully at the area of the head under the cam near the rear two cam bearings for little beads of water emerging, scooting across the surface, and disappearing down an oil return hole.

Unfortunately I have pulled the head now, I was hoping to find something obvious but I cant see any obvious problem or signs of leaks. Would the above indicate head gasket failure? What are the chances of having a crack in the block? that is my main concern atm. But I wasnt getting any white smoke (some drips of water when cold from exhaust). All the cylinders look the same colour, someone told me that is one cylinder had coolant leaking into it it would look a different colour and much "cleaner".

Would you be able to see a crack in the head with the naked eye? I cant see anything on close inspection.

[Brianmoooore]

2.5 head is notorious for cracking through the bottom of the rear two cam bearings and the deck between them. You make be able to make out a thin black line between the bottom of the two bearings, or, easier to see, a crack across the bearing surface, if you remove the cam.

[aimlessrock]

2.5 head is notorious for cracking through the bottom of the rear two cam bearings and the deck between them. You make be able to make out a thin black line between the bottom of the two bearings, or, easier to see, a crack across the bearing surface, if you remove the cam.

Brian is correct...with the cam removed the engine shop found a crack on my last head.

if its cracked its scrap sadly.

[steve_k]

2.5 head is notorious for cracking through the bottom of the rear two cam bearings and the deck between them. You make be able to make out a thin black line between the bottom of the two bearings, or, easier to see, a crack across the bearing surface, if you remove the cam.

Brian is correct...with the cam removed the engine shop found a crack on my last head.

if its cracked its scrap sadly.

not really. i had one crack on me a few years ago under the cam, took it to the cylinder head shop when it was still in saltfleetby (lincs) & got it repaired & fettled while it was there, still got it as a spare in the back of the shed somewhere.

[knapmann]

Ok an update on this is all bad,

I sent the head off to be pressure tested and re-skimmed and checked for warping etc. They told me that the pressure test cannot replicate running pressures and temps and that while it is 95% successful they cant guarantee it will show up failures. The head came back, it was reskimmed not warped and passed the pressure test. I looked for cracks in the cam journals by eye and saw nothing. I refitted the head today with new gasket and bolts.

The engine was steaming as it got up to temp which I put down to residual water coolant in the system but after 30 mins idling it was still steaming. I took the rocker cover off, there was fresh mayo around cylinder 5.Also saw what I thought were water beads running around the oil wells above the intake rockers of Cylinders 4,5 and 6. With all the turbulance it was hard to be sure, the "beads" would skate around then vanish as if they are just oil bubbles which are bursting or water beads evaporating suddenly.

I turned the engine off and when I went back to it I saw the below, where the oil has pooled near the 2nd to rear cam journal there is a clear little pool of coolant (my coolant is red like pictured).

I am assuming I have a cracked head at this stage, but the fact it passed the pressure test makes me wonder... any ideas of other possibilities? is it possible to DIY crack test? so much time, effort and money wasted now it seems

[Brianmoooore]

I am assuming I have a cracked head at this stage,

I'm afraid that your assumption is 100% correct. Time to write this down to experience, and source yourself a known good head or complete engine.

Your story closely mirrors one of my own from many years ago, and I can remember well the disappointment I felt when I finally realised that I'd wasted time and money rebuilding and fitting a head that was already cracked.
I solved my problem by buying a Cat. C 325SE completely unseen, just for its head.
We picked the car up in the middle of a thunderstorm, so didn't get a chance to inspect it until we arrived home three hours later.
Imagine my disappointment when I removed the coolant bottle cap and found traces of mayo inside! I'd spent a few hundred pounds and a day to get myself another scrap engine!!!
Anyway, the rest of the car seemed to be well looked after, with loads of parts in A1 condition, and there was a folder inside containing a large sheaf of invoices, so I started reading my way through them.
The very last invoice in the pile turned out to be just a few weeks old, was for around £1500 or so, and was for the supply and fitting of a shiny new cylinder head to replace a cracked one - the mayo in the tank was just the residual from the old one.
My mood instantly changed from despair to elation - for once in my life I'd hit the jackpot.

[aimlessrock]

sorry to hear, at least you did not find out stranded at the roadside...what number is on the head?

[jimbom30cab]

Thats a great story Brian, make me chuckle

[knapmann]

I am assuming I have a cracked head at this stage,

I'm afraid that your assumption is 100% correct. Time to write this down to experience, and source yourself a known good head or complete engine.

Your story closely mirrors one of my own from many years ago, and I can remember well the disappointment I felt when I finally realised that I'd wasted time and money rebuilding and fitting a head that was already cracked.
I solved my problem by buying a Cat. C 325SE completely unseen, just for its head.
We picked the car up in the middle of a thunderstorm, so didn't get a chance to inspect it until we arrived home three hours later.
Imagine my disappointment when I removed the coolant bottle cap and found traces of mayo inside! I'd spent a few hundred pounds and a day to get myself another scrap engine!!!
Anyway, the rest of the car seemed to be well looked after, with loads of parts in A1 condition, and there was a folder inside containing a large sheaf of invoices, so I started reading my way through them.
The very last invoice in the pile turned out to be just a few weeks old, was for around £1500 or so, and was for the supply and fitting of a shiny new cylinder head to replace a cracked one - the mayo in the tank was just the residual from the old one.
My mood instantly changed from despair to elation - for once in my life I'd hit the jackpot.

Hi Brian thanks for the reply, did your head pass a pressure test before fitting? from what I was told it would be VERY rare for a head to be cracked and not show up on the pressure test but maybe this is not uncommon on a 885 head. If my head is cracked then this is what has happened. At least it would not be an issue with the block which would be the worst from me.

I have put huge amounts of work fitting my M20 into my '02, its a hell of a squeeze to then find issues with the head and maybe even the bottom end is a huge blow to say the least. Not only this but my car was booked into multiple shows including Gaydon this weekend, all have to be cancelled now. My summer of fun has become a summer of expensive disaster.

I suppose I have a few questions still

1) What causes cracking? can it be simple fatigue or only over heating?

2) My engine never overheated to my knowledge so it can only be caused by air pockets in the head, what can I do to ensure it is fully bled? This doesnt seems so simple.

3) This head gasket has only been idled for 30 mins, do you thin I could get away with re-using it? it is my 2nd gasket and head bolt set in 3 months!

[knapmann]

sorry to hear, at least you did not find out stranded at the roadside...what number is on the head?

its an 885 325i head, I am on the look out for a known good one now!

[knapmann]

sorry to hear, at least you did not find out stranded at the roadside...what number is on the head?

its an 885 325i head, I am on the look out for a known good one now!

[knapmann]

I found a source for new heads!!!

http://www.ebay.co.uk/itm/BMW-E30-E34-3 ... 2a50824523

[Brianmoooore]

1) What causes cracking? can it be simple fatigue or only over heating?

Design fault is the short answer, although I cracked mine as a result of an airlock after a coolant change.

2) My engine never overheated to my knowledge so it can only be caused by air pockets in the head, what can I do to ensure it is fully bled? This doesnt seems so simple.

Fill slowly and carefully, then turn the heater on full when you start the engine and ensure it starts to blow warm in less than a minute. If it stays cold, and the temp. gauge starts to climb higher than it should, stop the engine immediately and bleed the air lock from the top heater pipe.

3) This head gasket has only been idled for 30 mins, do you thin I could get away with re-using it? it is my 2nd gasket and head bolt set in 3 months!

A used head gasket is a used head gasket, however new or old it is, and certainly can't be used with a different head. You might get away with reusing the bolts a second time, but don't quote me on that.

[Brianmoooore]

I found a source for new heads!!!

http://www.ebay.co.uk/itm/BMW-E30-E34-3 ... 2a50824523

A little cheaper at £534.28, from CP4L but "out of stock".
These are Spanish made, are supposed to be of good quality, and I've even heard that the design fault that cause the cracking has been addressed, but I can't confirm this.

[aimlessrock]

for the sort of sums your looking at - even £534.28 you could buy a complete B20 engine and drop it in, not as powerful as the B25 but plenty are around and heads are less prone to cracking.

Just a suggestion.

[HairyScreech]

For £600 you could be most of the way to fitting an M5x engine.

One way to check is pump the coolant system up manually on the car.

Get the car up to temperature and then switch off, fit a cap that can be connected to a pump and pressurize it.

You can then leak check at your leisure on a running temperature engine.

The AMC heads have terrible intake ports but give more meat on the castings for porting, stock they are poor but they can be worked to be better than the BMW heads.

I think I may have this issue on mine, but the mayo has only happened once and seems to have gone away, I am hoping it was just because of a breather pipe blockage.

[knapmann]

Success of sorts, I have found the crack today. It is on the ridge of the casting on the intake side, just in front of the 2nd to rear cam journal (exactly where the coolant pool was when pictured earlier). There was 100% no way you can see this crack without using detector, obviously it was going to be fine considering the pressure test didnt show it up. I am happy to an extant having bottomed the problem and establishing my block is likely OK.

Coincidentally I went to see Ian at Linwar BMW in Southport before I did the test and he showed me a head he had sawed in cross section after it cracked in the exact same place. In profile you could see the crack with naked eye, it was still tiny though. Low and behold mine is the same.

I suppose this is a lesson for everyone:

1. Bleed thoroughly

2. Dont waste time on pressure tests

3. Check for water droplets under the rocker before whipping the head off assuming gasket failure

4. Always listen to Brian.

[hennabm]

When the head on my 320 cracked a few years ago I bought a reconditioned head from Linwar.

Top bloke

[Andyboy]

All M20 heads can crack there. It can happen at random so not really related to coolant bleeding etc. The early E21 320 was the worst. They had electric cooling fans that would come on only when the engine was FH but the 323i had a viscous - no idea why.

A possibility as to why the heads crack can be thermal shock as the stat opens and the head cools rapidly.

Don't bin the cracked head as they can be repaired. You need to get them up to temp before they can be welded for the crack to open up. That's why a cold pressure test won't always show a problem.

The AMC copy cylinder heads are very good. They're made in Italy and I've never heard of one cracking.

[knapmann]

Don't bin the cracked head as they can be repaired. You need to get them up to temp before they can be welded for the crack to open up. That's why a cold pressure test won't always show a problem.

The AMC copy cylinder heads are very good. They're made in Italy and I've never heard of one cracking.

Most people on here have been saying a cracked head is junk and cant be fixed? or is this simply a matter of economy, I can get another head for £200; if repairing this one is more than that whats the point?

[daimlerman]

Don't bin the cracked head as they can be repaired. You need to get them up to temp before they can be welded for the crack to open up. That's why a cold pressure test won't always show a problem.

The AMC copy cylinder heads are very good. They're made in Italy and I've never heard of one cracking.

Most people on here have been saying a cracked head is junk and cant be fixed? or is this simply a matter of economy, I can get another head for £200; if repairing this one is more than that whats the point?

Point is that ten years ago a s/h head cost £25....
There will come a day when a repair will be cheaper!