Is this serious? Or did I do something stupid?

[Nigel Worc's]

Benj1984 said:

In my experience steve_bmw is correct, where modern cooling systems have an expansion bottle and a pressure cap, the cap has two phase, one to release the pressure then one to remove the cap. This doesn't work on jap cars with rad caps and reservoirs, but on most European stuff, you should be able to release the pressure and remove the cap. If coolant is boiling out of the bottle after cap removed then its under pressure, either from an air lock or from cylinder combustion pressure.

In my experience, NEVER remove the cap until the coolant is cool, by the time you find out something is wrong, you need the burns dressings from your first aid kit.

[steve_bmw]

Nigel Worc's said:

In my experience, NEVER remove the cap until the coolant is cool, by the time you find out something is wrong, you need the burns dressings from your first aid kit.

What cap? There are different systems, if you release the cap on the expantion tank slowly and you can hear and see water knocking on the cap then there is pressure, too much, as in a bmw's system there should only be a small amount of pressure in the bottle ant any given time.
I can quite happily remove the expansion cap after 300 miles with the engine still running and no water will come out.

[METHS]

eltax91 said:

OK chaps. Just traveled 2 and a half hours back home, THEN LET THE CAR COOL DOWN and then took a few pictures. It did need a top-up, but then I dont know how much i lost in the dark last night!





I should add, I have cleaned this gunk off the cap in the past. So, HGF? Or a good indicator the coolant cap needs replacing?

There should be no residue like that. Although, to me it doesn't look oily.

There is also no milky residue in the oil and the oil level hasn't increased? (Oil level would increase if water was mixing with the oil).

The residue could be some kseal/radweld that has been poured in to try and solve a leak? Doesn't normally look like that though.

Edited by METHS on Wednesday 24th July 23:49

[steve_bmw]

Nigel Worc's said:

You are joking ....... right ?

Or do you just like to see people scalded ?

Jesus, you see some crap written on forums !

Google boiling point of liquids versus pressure/altitude.

That's not very nice either, I only ever post on technical issues wher I know I'm right and can give the correct information.
Your right, you do see crap written on forums, usually from someone who has no idea what there on about!
I don't like to see anyone scalded, but in the case of the op's problem, the cap will unscrew along way before it blows off, giving you time to move away, if there is that much pressure in the bottle there is a fault.

[Nigel Worc's]

steve_bmw said:

Nigel Worc's said:

In my experience, NEVER remove the cap until the coolant is cool, by the time you find out something is wrong, you need the burns dressings from your first aid kit.

What cap? There are different systems, if you release the cap on the expantion tank slowly and you can hear and see water knocking on the cap then there is pressure, too much, as in a bmw's system there should only be a small amount of pressure in the bottle ant any given time.
I can quite happily remove the expansion cap after 300 miles with the engine still running and no water will come out.

I happily work on multi kilowatt 3 phase drive systems whilst they are live, sometimes, but I don't advise others to do the same.

Most people are not car mechanics, eltax most certainly isn't, and neither am I, most people wont know what type of coolant system they have, and will only normally be looking to check levels on a hot engine if they think there may be a problem.

So I at least think your advice is at best silly, and at worst stupid.

[AndrewO]

As said earlier, compression test is worth doing, plenty of vids on youtube to show you how to do it.

Take all the plugs out and test each cylinder, 150-160psi.

[Sump]

Nigel Worc's said:

steve_bmw said:

Nigel Worc's said:

In my experience, NEVER remove the cap until the coolant is cool, by the time you find out something is wrong, you need the burns dressings from your first aid kit.

What cap? There are different systems, if you release the cap on the expantion tank slowly and you can hear and see water knocking on the cap then there is pressure, too much, as in a bmw's system there should only be a small amount of pressure in the bottle ant any given time.
I can quite happily remove the expansion cap after 300 miles with the engine still running and no water will come out.

I happily work on multi kilowatt 3 phase drive systems whilst they are live, sometimes, but I don't advise others to do the same.

Most people are not car mechanics, eltax most certainly isn't, and neither am I, most people wont know what type of coolant system they have, and will only normally be looking to check levels on a hot engine if they think there may be a problem.

So I at least think your advice is at best silly, and at worst stupid.

I can easily take the expansion tank off my 996 when hot. Just crack it open slowly over a period of a minute and you're fine...

[Targarama]

Sump said:

Benj1984 said:

Targarama said:

These cars normally need a cooling system refresh around 100k miles - radiator, expansion tank, water pump, main hoses, thermostat and expansion cap. Have these been replaced in the car's past? If not I suggest getting the whole lot done. Read up about the 5 series straight six cooling system and you'll find lots of forums telling you this.

I never understand this kind of forum scaremongering. No car suddenly needs its whole cooling system changed at 100k. You service it regularly over its life and replace parts as they wear and start to fault.

+1.

It stems from over the pond scaremongering.

I agree the car won't explode into 1000 pieces at 100k. However, to ensure you are not left stranded as bits listed by me fail one by one this is the recommended approach for an E39 on the BMW forums.

[eltax91]

Thanks all (even you nige!) for the opinions

Car is booked into a highly recommend bmw specialist in leicester tomorrow for diagnosis. The recommendation came off another bmw problem thread I started here last month.

So, here's hoping 'the crack fox' knows his specialists.

[Herman Toothrot]

A coolant system is a closed system it makes no difference where you open it. If it is still hot I.e. about 86oc which tend to be normal running temp and you just open the coolant cap be it on a rad or expansion tank / swirl pot it will suddenly boil due to the pressure release, most are about 14psi. Very dangerous and shouldn't be done hence all the warning symbols telling you not too. Only exception is a coolant overflow bottle if the car has one that is after the pressure cap.

Not sure which cars have one after the pressure cap, my old mk1 mx5 did. My Audi, Mr2 and old vx220 didn't.

[Ozzie Osmond]

Dog Star said:

You've undone the cap, reduced the pressure hence the boiling point of the coolant. That's normal.

Yes, absolutely normal.

Just to reinforce this point you need to remember that ALL of the coolant is under pressure, not just the bit in the tank. When you release the pressure by opening the cap ALL of the coolant will boil, including the coolant INSIDE the engine. The increased volume of vapour tries to escape and can only move in the direction of the header tank, causing the dangerous surge of boiling coolant.

Tip: If you have a significant coolant leak one way to achieve "limp home" is to fill the coolant system with water right to the top and then drive gently WITHOUT the radiator cap and with the heater full on.

• the cooling system cannot pressurise so your leak will be slowed or stopped
• with a bit of luck you won't boil the coolant either and are likely to arrive at your destination with the system still full. Best to carry a spare can of water if you can though, and check from time to time just in case.

[Mr2Mike]

Benj1984 said:

I never understand this kind of forum scaremongering. No car suddenly needs its whole cooling system changed at 100k. You service it regularly over its life and replace parts as they wear and start to fault.

It stems from the fact that BMW of this era are notorious for cooling system failures as the car ages, so sensible people proactively replace the vulnerable parts to avoid breakdowns.

This is a technique known as "preventative maintenance", though the entire concept clearly confuses a lot of people who would prefer for parts to actually fail and cause them inconvenience before thinking about replacing them. No doubt the same people that will then declare the car unreliable and a money pit.

[Mr2Mike]

steve_bmw said:

That's not very nice either, I only ever post on technical issues wher I know I'm right and can give the correct information.
Your right, you do see crap written on forums, usually from someone who has no idea what there on about!
I don't like to see anyone scalded, but in the case of the op's problem, the cap will unscrew along way before it blows off, giving you time to move away, if there is that much pressure in the bottle there is a fault.

It's not the actual pressure that presents a danger, it's the fact that releasing the pressure can cause the coolant to spontaneously boil. Unscrewing the cap from a radiator or header tank with a hot engine is dangerous, no matter what you say.

If it's just an expansion tank then it only holds coolant that has already been ejected from the cooling system and shouldn't be pressurised at all.

[littleredrooster]

Mr2Mike said:

steve_bmw said:

That's not very nice either, I only ever post on technical issues wher I know I'm right and can give the correct information.
Your right, you do see crap written on forums, usually from someone who has no idea what there on about!
I don't like to see anyone scalded, but in the case of the op's problem, the cap will unscrew along way before it blows off, giving you time to move away, if there is that much pressure in the bottle there is a fault.

It's not the actual pressure that presents a danger, it's the fact that releasing the pressure can cause the coolant to spontaneously boil. Unscrewing the cap from a radiator or header tank with a hot engine is dangerous, no matter what you say.

If it's just an expansion tank then it only holds coolant that has already been ejected from the cooling system and shouldn't be pressurised at all.

You're wasting your keyboard fingers. He patently doesn't understand how a car's cooling system works or why it is pressurised.

[crossy67]

A compression test will tell you nothing of a coolant leak, well nothing a burst radiator or overflowing watery oil sump won't first.

Think about the pressures involved.
Water pressure, roughly 1 bar.
Oil pressure, what, 4 bar?
Combustion gas high enough to propel you and your car? We know at cranking speed pressures are iro 10 bar.

Has any one thought of checking the water pump? These can leak only when running and the water will tend to evaporate due to it's hot location.

[Sump]

Mr2Mike said:

It stems from the fact that BMW of this era are notorious for cooling system failures as the car ages, so sensible people proactively replace the vulnerable parts to avoid breakdowns.

This is a technique known as "preventative maintenance", though the entire concept clearly confuses a lot of people who would prefer for parts to actually fail and cause them inconvenience before thinking about replacing them. No doubt the same people that will then declare the car unreliable and a money pit.

I owned my 330d for 5 odd years and did 80k in it. In the first year the waterpump went, that was replaced. In the fifth year the coolant expansion tank went and that was replaced.

Did you seriously just say I would have been better off replacing everything in the first year as "preventative maintenance?"

There is a big difference between, the clutch needs doing, lets do the rear main seal as we are basically there anyway for a little sum to , the waterpump has gone, lets strip the system down and replacing everything for the lulz at £600

[Mr2Mike]

Sump said:

I owned my 330d for 5 odd years and did 80k in it. In the first year the waterpump went, that was replaced. In the fifth year the coolant expansion tank went and that was replaced.

Did you seriously just say I would have been better off replacing everything in the first year as "preventative maintenance?"

That would depend on how old it was when you bought it, and whether any parts had already been changed. And whether you don't worry about the potential inconvenience of a breakdown.

Plenty of people don't even bother changing timing belts, I would far rather have my car as reliable as it can be.

[steve_bmw]

I think you've missed the point of my first post, the only reason water will blow out of the expansion tank is if its super heated with combustion gasses from a failed head gasket, over filled or a massive airlock.
I am not suggesting whipping of the cap when you know you have an overheating problem, that would be silly.
Here is a video of what should happen when you remove the cap, I've just driven 45 mins, water temp of 95 degrees, pulled up connected the obd reader and opened the hood, when you crack the cap you get a small release of pressure, then remove the cap, water should not come out. If you crack the cap off and water pours out you have a problem.
In 10 years of working on bmw's I have only ever seen boiling water blow out of the cap due to failed head gasket or overfilled, wether its an e36 e39 x5 z4 they all behave the same.

http://youtu.be/Wx8fQzD-yQs

[Jimmyarm]

I haven't looked close enough at an E61 expansion tank to know for sure but, on the E39's the expansion tank on the side of the radiator can fail internally meaning water doesn't circulate properly which causes the cooling system to get too hot and over pressurise blowing coolant past the cap. The tanks also crack and leak which can be hard to spot as they tend to hold pressure on the test when cold.

Its worth looking further into the tank before assuming the head gasket has failed, there are other sneaky locations they leak from that are hard to spot as well but a decent specialist will know what to look for.

[Sump]

Mr2Mike said:

That would depend on how old it was when you bought it, and whether any parts had already been changed. And whether you don't worry about the potential inconvenience of a breakdown.

Plenty of people don't even bother changing timing belts, I would far rather have my car as reliable as it can be.

I think it was 3 years old and had 70k on the clock.

Again, timing belt has a fixed time which is dictated by the manufacturer.