M20 B25 rattles and cooling.

[tourer-dan]

Well here's the story: (welcome to my first post!)

I bought an E30 touring 325i about 6 weeks ago on the basis that it needed a new camshaft. The lobes were all visibly worn and it sounded like a diesel sewing machine.

No problem, replaced the cam and rockers, did a major service on the way, screwed it all back together.
started it up, all lovely, then idled really unevenly once it was warm.
Did the tappets again and all was a bit better.

It still sounded as though one tappet was still out, although I knew they were all fine, so I went to the local specialist today who said the engine was too 'quiet', ie the clearances were too tight causing a slightly uneven idle. He said the odd tappet noise could be a sticky compression ring and sent me away to do the tappets again and run a flush through the oil.

OK so far?

Drove to my parents this evening which is an hour dwn the country lanes and my first real chance to give it some welly since I've done the work ( I haven't done the tappets again or the flush yet)
Just before I got there the coolant check flashed up. I checked it when I arrived and there was no pressure in the system (the cap just unscrewed with no drama) and it needed a litre to top it back up to max. There is also a smear of mayo on the underside of the oil cap (but none on the dipstick)
SO:
Should the pressure cap just unscrew from a hot engine?
Where could the water be getting into the oil? (bearing in mind I've just replaced the head gasket anyway)
Have I made a boob along the way somewhere with reassembly? (the performance is fine)
Was the new HG faulty? (It was an Elring set)

When I got home again tonight (another hour's drive home), the water level is fine, although the system still seemed to have no pressure.

I really don't want to take the head off again.

Help me out guys!!
Dan

[Davenotouring]

The expansion cap should just come off unless it's really hot. This is a good, not a bad sign.

The mayo, well that could be condensation.

Do you notice any oil in the water?

Here's hoping you've made no mistakes along the way.

How much water is it using?

[johnono]

o mate i dunno.. did u use new head bolts? i dunno dude , bit too tech for my levels but dont worry help is on the way, but dont drive her

[tourer-dan]

Well it's the first time I've checked the coolant since I did the work ( about 2 weeks and 250 miles ago), so I was hoping maybe it's just gone down as a couple of little air locks have disappeared. I am more worried by the mayo combined with the coolant drop - mayo at this time of year?

Seeing as I was driving hard, it could either be as I said the last of the air, or the extra coolant pressure leaking coolant into the oil through the weak spot (wherever it may be)

What do you reckon is the quickest way to check if there's water in the oil?
there was none apparent on the dipstick, but there was some condensation on the oil cap.

[Brianmoooore]

The cooling system should be under pressure when you remove the cap on a hot engine immediately after stopping the engine.
Check your radiator cap has a yellow disc on it's underside and not a black one. Was a recall and should have been changed years ago.
If it's black and you give your dealer the VIN, you should get a free new one.
The fault with the cap is that it sometimes over pressureises the system and blows water out of the radiator seams or heater matrix.
Being optimistic, your apparent water loss could just be air finding it's way out after your rebuild. Being pessamistic, an airlock after refitting your head could have cracked the head.

[tourer-dan]

I have the stamped recall docket to say the pressure cap was done.

I think the best thing to do is to carry on for a while and see what happens. The car isn't overheating at all, the needle atays upright all the time (except when it has one of it's flickering fits, but a smart tap on the dash usually puts it right again)

I'm prepared for bad news, so watch this space for an update....

Is it really necessary to replace the head bolts EVERY time?

and how about the gaskets, the HG obviously only goes once, but how about inlet and exhaust gaskets? Surely it would be cheaper to buy HG and thermostat gaskets on their own.

[Brianmoooore]

Still check the coolant pessure cap has a yellow centre disc on the bottom - It may have been changed back.
I think you may have had a lot of air trapped in the head. Do you know if the heater was working properly after you replaced the head?
Filling an M20 with coolant is quite an art.

Head bolts can be used twice in practice, and I have been known to reuse the odd inlet and exhaust manifold gasket occasionally, as long as the same manifold is going back in the same place.

[tourer-dan]

When I filled it, I massaged the top hose until all the air had been squeezed out, fitted the cap, then run it up, priodically releasing the bleed screw to let some air out. I've got to say there wasn't much air in.
I read that filling would be a task and have to say I found it remarkably drama free.

As far as I could see, The head has 2 separate coolant passages, one for the valve seats which drained around the inside into the block (or out through the rear elbow) and another which drained around the outside. Are you saying the inner chamber could have been airlocked and that I have cracked the head?

I've got to say putting in a new camshaft was not the magic wand I thought it would be

[Brianmoooore]

Sounds like you've some idea of how to fill a M20 properly, but they can still airlock. The main symptom is that the heater won't blow hot, and the air has to be released by partly removing the top heater hose.
i know from experience that this airlock can crack the head.
If it wasn't airlocked, and the water level isn't dropping now, then the questions remains as to where the water went and to why there's no cooling system pressure?

[tourer-dan]

Yeah it's a bucket of shite.

I really don't want to have the head off again, within 3 weeks after spending so much time and effort reconditioning it just to find the sodding thing has cracked. I think it's more likely something like the HG not sealing properly, I'll just keep my eye on the oil and coolant for a while to get a better idea before I get the tools out again...

I'm going to bed to sulk now.

[Geeman]

tourer-dan... just as an aside... the flickering temp guage is caused by the guage itself being loose. I had the exact same problem. It would flicker, then I'd tap the dash glass and it would jump back to the normal temp reading.

I took the clocks out and the nut holding the guage on to the binnacal was missing. l Found one to fit, tightened it up and it never flicked again. Sorted.



Giles.