How does your coolant float, float ?

[Rob_benton]

Morning

I have a 05 3.0.

When I top up the coolant to the max, a few days later the float reads minimum.

My independent has pressure tested the system and says its fine with no leaks.

My question is, is it normal for the coolant system to loose a bit of coolant until it gets to minimum and then just sits at the level ?

Thanks

 

[nfarmer]

Morning

I have a 05 3.0.

When I top up the coolant to the max, a few days later the float reads minimum.

My independent has pressure tested the system and says its fine with no leaks.

My question is, is it normal for the coolant system to loose a bit of coolant until it gets to minimum and then just sits at the level ?

Thanks

Thats what mine does

 

[Stuart Truman]

If your indie has tested it I wouldn't worry too much. I assume the car is running ok otherwise?

 

[Rob_benton]

Yes it's runs fine.

I'm glad it sounds normal.

 

[edd_jedi]

Mine does exactly the same. I've been keeping an eye on it as I trust BMW cooling systems about as much as Jimmy Saville!

 

[cj10jeeper]

Well it's not normal to use any coolant. Mine goes years with no top up.

I'd suspect a cracked header that leaks only when hot. Several guys have had this fault.


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[GreyZed]

Something is wrong if you are losing any coolant at all. Maybe the hairline crack issue with the header tank that weeps when hot and expanded or a hose union somewhere doing a similar thing. My filler cap was letting coolant blow off even when fully tight and a new cap fixed it for me. Look for tell tale dried splash marks or staining in the engine bay and underside of bonnet.

 

[ranski]

O rings, expansion tank or the cap hasn't been tighten properly

 

[sam1832]

Mine is right to the top all the time

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[paddy wright]

may be a stuck thermostat

 

[cj10jeeper]

may be a stuck thermostat

Doubt it as modern stats fail open and if by chance it failed closed, the engine would overheat within a mile or so.

 

[Rob_benton]

I don't think it's the thermostat as the engine warms up so quickly.

The mechanic said he pressure tested the system with the engine at running temperature so I would of thought any hairline cracks or leaking seals would have shown up.

 

[cj10jeeper]

I don't think it's the thermostat as the engine warms up so quickly.

The mechanic said he pressure tested the system with the engine at running temperature so I would of thought any hairline cracks or leaking seals would have shown up.

Look at this logically. You top up and after a few days the coolant level is back to low. That means water is getting out.

It's going one of 2 places Into the engine or leaking outside the system.
If it were in the engine you'd have mayo on the filler cap, so you can easily rile that out.

It's therefore leaking out (be that in the engine bay or inside the car and because it takes a few days and nothing is visible then it happens under pressure and slowly.

You mechanic would not see a pinhole leak as it likely vapourises off on the hot engine or comes out as fine vapour and probably only under road stresses.

Since a crack in the header is a known issue of these then that's where I'd start as as Ranski points out the others like hose clamps.

 

[paddy wright]

may be a stuck thermostat

Doubt it as modern stats fail open and if by chance it failed closed, the engine would overheat within a mile or so.

This was the reason my z was losing coolant- never overheated, just lost coolant- the dial never raised above normal.

 

[Dukester]

Haven't posted for a while as car off the road in storage. I have same problem as mine does the same. I start it up and move it around a least once a month. I just checked the water levels and mine was down so I topped it up (1/2 litre) and two days later checked again and down again (1/2 litre). No signs of leaks etc and temp gauge normal. I'm only running at idle for most of the time as in the driveway. No issues before I stored away

weird

Dukester

 

[grayboots]

Mines been doing this for a while now. Took it to the garage and they said they could not find the leak, but had spotted staining by the water pump. Took it home and ran it up to temp on the drive whilst checking the expansion tank for leaks, nothing. Then I saw a tiny wet patch next to the water pump right were the staining was. It's coming from the thermostat housing. Looks a bit fiddly to get at, but it's top of the todo list.

 

[Rob_benton]

I noticed the seal around the inside of the expansion tank cap was dirty.
I cleaned it up and haven't seemed to have lost any coolant since.

Hopefully it wasn't sealing properly.

 

[Dukester]

Sorted - sensor near bottom of rad was leaking