L322 Coolant System explosion

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Originally Posted by RangieBit

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12. Start engine, bleed air from cooling system and allow engine to reach operating temperature.
13. Fit and close expansion tank bleed screw when a constant flow of coolant is emitted.
14. Visually check engine and cooling system for signs of coolant leaks.
15. Disconnect battery earth lead.
16. Wipe coolant from chassis and surrounding area.
17. Fit engine access cover.
18. Top up cooling system.
19. Connect battery earth lead.

I think they are suggesting that steps 15-17 take long enough that the system has cooled sufficiently. Topping up the coolant should only be done when the system is not at full operating temperature. The top up procedure is in the owners manual. I think there is a graphic on the expansion tank also about the float position for reference as well.

Hope this is of use to you.

Cheers,
Iain

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Hello Iain, I drive a L322 on the other side of the globe (Sweden) but the other day I came to grips with a problem I had with radiator hose overpressure.
My expansion tank cap was faulty, and in a one-way-valve fashion allowed air to be sucked in when the engine cools down (some vacuum occurs when the fluid contracts). Then upon engine warmup the fluid and trapped air combined would cause over pressure. The new cap (same 140 rating) does not allow air to be sucked in and I notice when the engine cools down it even sucks the radiator hose a bit flat from vacuum. This seems a good thing because when the fluid expands the flattened hose will take up fluid volume as it expands and finally at full operating temp the hose pressure seem quite normal.

So connecting to what you said, if I would open up the cap with cold engine to do some topping up I will lose that vacuum. Then upon warmup I assume the pressure will build up now going from neutral/no pressure up to a bit higher than if I began from vacuum. I assume this would mean the cap hopefully reach a limit to release any overpressure?, thus can I assume the cap pressure limit actually works to calibrate the hose pressure ? Otherwise at what temp "halfway" that would be suitable to do the topping up at seems a vague thing. In my homebrew way I would rather monitor the pressure buildup and unscrew the cap a bit to let some subjective excessive pressure out at the cap at full temp until hose stifffness feels good to my taste.. Then upon subsequent cooling down the system will again go into a vacuum state sucking the radiator hose a bit flat. :)
Well I am not sure about how that cap pressure release works. Anyway the behavior I am getting now looks good to me. The top hose of the radiator goes from sucked a bit flat when cold up to some decent pressure at normal temp and I am pleased so far the way this works. At least when I return to the car the next morning and find the hose still in vacuum state at least it tells me I have no air leaks. :angel:

Hi there Gunnar,

I don't profess to be an expert in these things (in fact far from it!) though one thing does occur to me.

According to the recommended coolant replacement procedure which you have quoted, the cleanup/top up step is done after the engine has been to normal operating temperature so that the thermostat is open and the fluid was freely circulating through all of the cooling system. This so that any air, if present, will be in the top part of the system.

I don't know if your shrunken hose is normal or abnormal as the climate here does not get truly cold to the extent that you would normally experience.

I'm also willing to defer to other owners in the northern hemisphere here but even in -10deg C alpine conditions in Australia I've never seen a partially collapsed top hose in a properly functioning system. So if anyone out there in a truly cold climate can confirm if this normally happens I'd appreciate also. Anyone out there in northern Canada perhaps?

If your service centre checked the coolant level when they replaced the cap to ensure it was OK then I'd be inclined to think this may be normal in your very cold climate.

At worst here it's not a complicated task to check the coolant level as per the owners manual although I probably wouldn't do it first thing in the morning. Perhaps, if possible, an hour or so after the engine has been run to normal operating temperature and then cooled down, so that the coolant is less likely to be under any pressure and not yet truly ambient temperature cold.

As a base line, if the system seems to be operating normally now then your shrunken hose when the system is cold (as in first thing in the morning cold) may also be entirely normal.

Hope this helps some.

Cheers,
Iain

Hello my earlier post on 140 cap and sucking hoses flat is not a good solution.
I finally ended up discovering that the cap I had replaced had a 200 pressure rating. And when I reinstalled that one my problems disappeared, part from that running with high pressure water hoses is kind of setting life up for excitement.
I will bring this up with an authorized service centre and hear what they have to say about why certain series require the 200 cap.

A cross post from another thread:

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Originally Posted by p38arover

I've noticed that my car's coolant level keeps dropping. I hadn't found any obvious source of leaks until last Saturday.

My coolant expansion tank is leaking down the RH rear corner - there is a tell-tale white streak which, after being cleaned off, returns after the next run.

Looking at the Full Fat RR forum to see if leaking tanks are common, the general consensus is that the BMW M62 4.4 V8 cooling system should have a 200kPa cap, obviously to allow a higher pressure and thus higher operating temps.

Perhaps this is the reason for coolant leaks. I'll replace the expansion tank but I'll leave the 140kPa cap in place for the moment.

My L322 runs at 99-100 deg C on the motorway but soon rises to 103 deg C in traffic (temps according to both ScanGauge and the L322 Message Centre).

Edit: I just had a look at MicroCat and found the cap specified is:
Up to VIN (V)1A001049, it is PCD100200L (which is probably the 200kPa cap)
From VIN (V)1A001050, it is PCD100070 which is the 140kPa cap.

My car's VIN is 34A145nnn so I don't know why it had a 200kPa cap.

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