Potential headgasket failure.

[Eddie.]

Okay, as mentioned in another thread, I think my headgasket may have died.

When I recently bled the coolant system, a fair amount of white foam came out from the radiator, it did eventually stop.

Also my heaters don't work, I've got to check the matrix isn't blocked, but it probably isn't.

So, both of these point to potential headgasket failure, if this is the case, how easy is it to change the gasket? Will I need a cam locking pin? Is there anything I should know about the procedure before ordering a gasket?

Also, could the above problems be linked to anything other than headgasket?

Thanks,

[Jeroen]

There are a lot of topics on head gasket failure, including very recent ones and including the description in the FAQ section. There are several other options like too much water in the coolant and an air pocket in the cooling system preventing flow. Rule those out first, do some proper checks on symptoms like a hydrocarbon fumes test on the coolant system, compression test, check on the spark plugs for discoloration.

In many cases it's not the head gasket and it would be a waste of money and effort to find that out halfway the process. Replacing the head gasket is pretty straight forward with a repair manual in hand, no special tools needed. But the head may be warped, cam/rockers worn, valves needing grinding, perhaps new guides, at least new stem seals, to do a proper job. So it can prove more time and money consuming than you'd expect at first, hence better first make sure it's the head gasket.

[Eddie.]

Okay, so compression test wise, would this work on a 316 engine?

http://www.screwfix.com/p/engine-compre ... tAod3msAIQ

Thread adapters are 10, 12, 14 & 18mm

What are the acceptable values I should be seeing on a healthy engine?

Cheers.

[Reck]

That should work. < 130psi = bad. 135-150psi = good, with no more than 10% variance between cylinders.

[Eddie.]

Thanks very much mate.

Also, and this is a little random.

The spark plugs, what size socket are they? I tried one the other day and it didn't fit, I've read that it's a 21mm, is this correct?

[Reck]

That sounds right, but they can be a swine to get out as there's very little clearance so you need a really 'thin' socket. I found the spark plug removal tool in the boot lid toolkit to be the most effective!! Just thought, double check a spark plug on those adapter sizes.. Also, make sure your valves are properly adjusted before performing a compression test.

[Eddie.]

The valves? What needs doing to them?

Sorry, I'm still learning

[Reck]

Sorry, the valve clearances. They're not self adjusting so you'll need to do it periodically. It's not too difficult, just a bit fiddly. Decent write up here;

http://www.bmw2002faq.com/content/view/21/32/

[Jeroen]

Most important for a correct measurement is that they aren't too far off. And always measure with throttle fully open otherwise you don't get enough air in to get to a decent compression.

[Eddie.]

So you're suggesting that I sort the valves, then refit the cover and do a pressure test?

Would I get an accurate enough reading without doing the valves? Remember, for now I just want to check the headgasket isn't finished.

Next year the engine will be getting some TLC.

[Reck]

Bad adjustment could be the cause of some of your overheating issues (although unlikely I'd guess). Personally I'd do them anyway, and at least you're ensured an accurate reading. Might be worth asking creedon if he did it at any point, might save you a job if it was done with the last 10k miles/couple of years. Also as Jeroen said, make sure the throttle is wide open.

[Eddie.]

Throttle wide open for the valve adjustment? I know to have WOT for the compression test.

Hmmm I don't mind doing it, but I'm still learning and I kinda don't want to make a mess of things! If I adjust them incorrectly, I could cause some damage, so I'm a bit unsure.

I'm all for having a go, don't get me wrong, just don't want to break my engine!

[Reck]

No, for the compression test.

Fair enough! I have a habit of creating two new problems for every thing I fix.

[Eddie.]

Yeah, I thought you meant for the compression test! haha

I know, a few of my friends have had older cars and have reset the valves and they claim it's a doddle, so I'll get on it.

Even if it's good practise I guess.

I just want too diagnose the problem really, so I know what needs fixing!

[PeteK]

IMO I'd do a quick comp test and see what you get. On an M10, it should take 30 minutes, less if it goes easily and you have a friend to help. I did the M20 by myself the other night.

If all readings are good, move on to other potential causes for your coolant and heater problem. If the readings are below 100 psi, you've got a big problem. If they're just a little different, look at valves.

Once you've got your confidence up, adjust the valve clearance then.

Don't forget to take out the fuel pump fuse and disconnect the coil so you don't get fuel or spark while doing the comp test.

Let us know how you go and post some of your other symptoms.

Good luck!