E39 strange symptoms RE cooling system

[Daniel 36]

Hi team,

I'm in the market for a car, and I've just looked at an 01 E39 530i. 

As I was unscrewing the cap to check coolant level, it started overflowing, and I could feel the bobber being eager to be free from constraint. The amount that overflowed wasn't significant. The guy said he had driven it for an hour, part of the trip being a large windy hill (this was yesterday). I suspected that a little pressure buildup wasn't too strange.

Anyway, I took her for a drive and there were no warning lights or anything, temperature sat where it was supposed to be. In fact, she drove beautifully. On turning the car off, it then told me to check the coolant level... It seems strange to me, as, if there was an actual problem it would tell me that during driving, right?

My question is, is this easily explainable? I understand that the answer is likely to be "get it checked out" but I thought I'd ask here first anyway. Probably should have taken photos for reference, but I didn't. TIA.

[BreakMyWindow 1878]

Any recent work done to the cooling system, or any done at all ? By now i'd expect it to have at least the expansion tank, water pump, radiator and the odd hose replaced. If you do end up buying the car, and keeping it for a while, plan to renew all of it if there's no evidence of recent parts replacement.

The check message could be a faulty sensor, but I'm leaning more to the "get it checked out" likely conclusion you've drawn.

[qube 3570]

if you unscrewed the cap after the car was driven (shouldnt normally do this if engine is hot) then that might explain the overflowing.

the check coolant level warning could be a faulty sensor as martin mentioned above, and as per his suggestion, would definitely do an overhaul unless have receipts to prove it was done.

 

How long has the owner had the car for? does it have other service records and does it look like a well maintained car otherwise? does the owner look trustworthy?

If yes, then I would give benefit of the doubt if everything else checks out and price is good.

If the owner doesnt know anything, has no records, short ownership, then I might jump to the conclusion that there might be a failing HG or cooling system leak somewhere but its all speculation at this point.

 

 

[Eagle 1679]

Temp gauge isn't very precise, it basically displays 3 options - cold, wide operating temp range and overheated. You need to access the hidden obc menu while driving to get the real coolant temp reading (easy to see if the thermostat isn't operating correctly also which is a common fault)

Adding to the above you really to set the correct level when fully cold, check no air in system or leaks once hot, then re-check the level again when fully cold. Hard to do when you don't own the car unless the owner has a clue, so pretty much have to get it checked by someone else. 

 

[Daniel 36]

Thank you for the responses, much appreciated. Coolant check was performed when completely cold.

There's no service history, but I had budgeted for the cooling system overhaul  
3pedals your breakdown is great, cheers. Based on that, it seems likely to me that:

it has a faulty sensor and coolant has been overfilled in response.
or
it has a leaky HG.

I highly doubt any recent maintenance, and can therefore pretty confidently rule out improper bleeding.

Now I just need to decide on a PPI or walk away. Still confused about why the warning would occur only after turning the car off and not during driving, but I have a better understanding of the situation now. Thanks all

[qube 3570]

Any more details about the car? Specs, price etc?

[Daniel 36]

2001 BMW 530i 530I M Sport | Trade Me Motors

I wouldn't be paying his asking price. Needs new head unit, dash pixel repair, and nasty crack in the bumper.

3 private owners since imported in 2012. According the guy, the last private owner had it 4 years and the one before him, for 5. Current owner is a smalltime RMVT who buys from dealers and onsells both privately and to other dealers.

I suspect that it's been very well looked after for some of it's life, but that the last owner was negligent or lost interest when he decided he was going to trade it in. Still deciding between PPI and walk away.

Leaning towards walking.

Edited January 12, 2021 by Daniel
Added words.

[Allanw 1072]

This thread explain the gauge readings.

 

I read the EEPROM from my cluster, and changed the gauge to read more useful numbers. The gauge readings were 100% waste of time - like the lights in modern cars.

 

[Eagle 1679]

21 hours ago, Daniel said:

Leaning towards walking.

I would given its an average condition Jap import. Better to get a decent condition NZ new example so you get proper plate trim, RF keys, EU2 emissions etc. 

[Daniel 36]

yeah decided that way this morning. 

Thanks for educating me on the unreliable temperature reading on the dash btw @Eagle I wasn't aware of the useless buffer. Cheers @Allanw too, I've made a mental note about having the gauge changed on any future purchase.

[BreakMyWindow 1878]

What’s your budget ? Well sorted ones go for 7k +. Projects typically float around 1500 - 5k depending on how much needs doing. 

[Daniel 36]

Working with a budget of up to $5k leaves me with a little set aside for insurance against unknown immediate concerns. I'm quite skint at the moment so I'm after something that won't need anything urgent in the next, say, 3-6 months.

I don't mind getting something that needs some work, just one that doesn't need work right now.

 

[KwS 2429]

Wholesale dealers like that buy the rubbish the dealer that traded it doesn't want to deal with themselves. They pay almost nothing for them. I'd keep looking unless you can chop a decent amount off that price. 

[Kiwi_BMW 89]

It could have an auxiliary pump that is playing up, I've known them to show symptoms like you describe.