Sudden coolant loss

[Sparrow]

Good Saturday of motoring with the roof down on the Z4 in the sun, 150+ miles. Checked the usual fluids, levels etc Sunday evening. Coolant cap was really difficult to remove (engine cold) initially thought it was cross threaded. Coolant level was maybe a bit high, the float was at it maximum height.

Drove 10 miles this morning as usual, 2 hours later noticed a large puddle of fluid under/dripping form the car. Under tray full and dripping out the the small home in the center.

Coolant cap removed and float at its now at the minimum.

I'm hoping that its just a case of me not fully tightening the cap, system has pressurised as it drove then gradually worked it way out the loose cap.

I'm confident that it was as tight as my other vehicles but it was definitely not as tight as what I removed yesterday.

I couldn't see any obvious hose split/cracked expansion tank. Just seems a big coincidence that its happened the next drive after I'd checked the level

Any thoughts/opinions would be appreciated guys

 

[patriot66]

What engine and year is your Zed ? It would be difficult to cross - thread the cap as it's quite a chunky, square thread. Also, if you tightened it reasonably then it shouldn't leak. Check the rubber seal is intact. I would suspect the expansion tank is cracked. You won't necessarily be able to plainly see a crack. Mine cracked a couple of months back and it was on a concealed corner so couldn't be seen until I removed it. Fill your tank with water and go for a short drive until the temp gauge is at normal, preferably back on your drive way. Leave it running and open the bonnet. Carefully (it's hot!) look or feel for a leak around and under the expansion tank.

 

[MACK]

+1 expansion tank, had to do mine on the zed and it's a really common failure on all bmw's of this vintage.

 

[Sparrow]

Thanks for the replies

It's a 3L, 2004. I've been reading about others experience with cracked expansion tanks. Just think it's a big coincidence that's it leaked literally the next drive after I checked it.

Would distilled water do for now? Coolant change planned in soon anyway.

A bit wary about driving it without knowing how severe the leak is

 

[Stuartt]

My expansion tank let go at the weekend, not the usual split but a small pin hole took a while to locate to be certain even with the system pressurized to 15psi.
Still it's all stripped out now and I'll be putting a new one in at the weekend.

Stuart

 

[patriot66]

Mine cracked completely without warning and I also check my levels at least once a week. My wife had been shopping 10 miles away and was luckily just 500 yards from home when the coolant level warning came on Anyway, distilled water is fine. If you don't fancy driving it then just let it idle until the temp shows normal.

 

[Sparrow]

Mine cracked completely without warning and I also check my levels at least once a week. My wife had been shopping 10 miles away and was luckily just 500 yards from home when the coolant level warning came on Anyway, distilled water is fine. If you don't fancy driving it then just let it idle until the temp shows normal.

I'll top up with distilled water tomorrow then (Tescos?). I guess I should see the coolant level light come on if it drops as I drive.

Thanks for the help

 

[csm180]

Hi mine went in the e85, if the level only goes down when you have driven a while, the expansion tank would be my guess. Open the bonnet and look down onto the engine tray before and after to see if it had only leaked during your drive. Best of luck finding it. My level light never came on as it is the expansion tank not the rad.

 

[Jmcg666]

I had the same problem and thought it was the reservoir; cap felt like it was cross threaded but it was actually just a knackered cap. Replaced cap and hey presto.

 

[jayd1000]

Mine went also, took a few weeks to figure out where it was coming from. Sometimes I would come home and park on drive and nothing, but then sometimes there would be a small drip, but couldn't see where coming from. Mostly happened if in traffic and car got hot, think the heat expand the tank. I changed cap just incase but to no avail. Changed tank as last resort, and there it was a slight hairline crack.