Today was very warm so after arriving home I decided to check all fluids levels, I soon found that my coolant reservoir is above the full mark! I just went outside to see where the coolant level is (20 min. later) and it's now just above the "full mark". The only work I had done to my car is last week the dealer removing my transmission to replace the flywheel and all clutch components, no other work was done.

What causes this to happen?

 

Yikes.

Coolant expands as it heats up (it is a liquid).. but there should be sufficient air space above it to keep pressure on it from boiling.

For starters.. replace the coolant cap. If pressures get too high, it should vent to atmosphere.

Second, I always assumed it should be at the full mark when warm (hot).. but no where near what you are looking at.

Things that come to mind with that much coolant is items like head gaskets..

Do you have a coolant gauge in your car? Like a scan gauge?

Might try this - and make sure its not near overheating -

 

No gauges, I did hear air escaping when I went back out there to check it, I remember when I didn't know any better I would unscrew it while the engine was hot and it would rush upward trying to escape, it's doing the same thing now even when closed. Why is it that everytime you take you car to the dealer something else rears it's ugly head? The dealer must have had to remove the coolant tank to get at the transmission right?

 

I bet you might have air in the system. Maybe they needed to remove it or something. I would try to bleed it once. then see if it continues to happen. But that video is also a good thing to try. I will have to remember that!

 

This.. Or they left it loose so it didn't hold pressure.

 

Good point! Nice find on the video Dan!

 

Lets assume they must have moved or at least unplugged the reservoir to remove the transmission, what's the procedure for bleeding? I know where the bleed screw is located.

 

I'm mobile so I'm assuming that you have an R56 https://wiki.bentleypublishers.com/p.../view/41058306

This is good for a complete flush, I would do this if you haven't changed all the fluid in a while.

 

I made a video of the reservoir, does it look like the coolant is boiling? I took it to my dealer and they said it's perfectly normal for this to have in the video. Somehow the drips of coolant is being released around the outside of the coolant reservoir. They say this is normal.

 

Still looks way over full...?

I'll shoot my car in a bit.

 

What mine looks like, fully warmed up. Cooling fan had just cycled off.

I'd say yours is way overfill?

 

[quote= i'd say yours is way overfill?[/quote]

+1

 

Looks overfilled, should be like danjreed. Is that coolant MINI Factory Blueish coolant, the color looks odd in the container , but those expansion tanks can yellow a bit with age vs new. I just wanted to make sure if it is something did not contaminate it.

Thanks

 

The aux water pump sounds like it has air bubbles in it just like when my thermostat housing started leaking last year, it was then the coolant was replaced by the dealer. That yellowish color is stuff attached to the walls of the reservoir, the coolant looks blue when you look through the cap hole. I'm going to attempt bleeding the cooling system later today or in the morning.

How is it that coolant can expand when hot? I thought only air could expand.

 

Everything expands with heat.

Liquids do, oil, water.. Not all at the same rate.. But they do.

Older cars had an "overflow" tank that allowed expanded coolant to fill a tank.. Later as the car cooled, the coolant would be sucked back into the system.

As thermoplastics got better, designers just put the pressure cap on the tank (now called an expansion tank or degas bottle..)

 

I have to go buy some Mini coolant, distilled water and a longer screwdriver.

 

I dunno, you got a lot of coolant in there.. I'd just get the screwdriver.

 

What are the chances of air trapped in the cooling system?

 

At this point since you have been driving it.. Pretty low. I mean I don't think it will hurt to open the bleed screw, you might get a little burp out but don't expect a 10 second long air bubble to hiss out.

 

How many turns to open the bleed screw?

 

It does vary on how many turns.. I turn it till coolant starts to come out. It may take several bleeds. I did have a MINI come in awhile back that was a pain to bleed all the air out! But once I did get it all out..things were all good!

 

I failed miserably, there's more air than before. (1) turn on ignition and set heating control to maximum temperature, (2) set fan to slow setting and
(3) release vent screw located on thermostat housing. Then started up the engine for the first time today, I observed only coolant flowing out of bleed screw until I noticed reservoir level started to drop. Then I shut bleed screw and the video below shows the rest, there's a **** load of bubbles shooting up from under the reservoir. The bubbles start at the bottom of reservoir.

What went wrong?

 

Were you bleeding it while it was running and at normal operating temp.?

 

The instructions do not specify, I followed the instructions to the T as if I were a robot following programing.

1. Turn on ignition and set heating control to maximum temperature.
2. Set fan to slow setting.
3. Release vent screw located on thermostat housing.

This is exactly what I did.

 

Should be running and warmed up..