[Snyperx]

So i just had the water pump and thermostat replaced in my 2006 325i a little over a week ago. On the way into work this morning I was pulling into the lot I park in and noticed a wisp of steam from the passenger side of the hood. I popped the hood and saw that my coolant overflowed. So there was coolant in the engine bay and under the car again. I never got a overheat warning or anything on the dash. I have been driving the car for about week and this is the first time since the pump replacement this has happened.

I plan on taking the car in, but was wondering what could be causing this? All I know is the dealer better fix it because I don't have another $1000+ dollars for another repair.

[N0OS3]

who fixed it? i bet there was a loose hose somewhere that popped off.

[Snyperx]

Originally Posted by N0OS3

who fixed it? i bet there was a loose hose somewhere that popped off.

The dealer. The overflow was via the tank though. You could tell because the frame rail and fender was all soaked.

[CombatNinja]

I'll bet your issue can be fixed by picking up a new expansion tank cap. On a 2006, it is likely that you no longer have a tight seal which is causing pressure loss which in turn lowers the boiling point which leads to a mess. Try that first.

[N0OS3]

Originally Posted by CombatNinja

I'll bet your issue can be fixed by picking up a new expansion tank cap. On a 2006, it is likely that you no longer have a tight seal which is causing pressure loss which in turn lowers the boiling point which leads to a mess. Try that first.

+1 to this then if there is no loose hose. :/

[Snyperx]

If that is the case, why now? As I mentioned I have been driving it for closer to two weeks and then today it does it?

[CombatNinja]

Coolant system overhaul tightened up the system and now made the expansion cap the weak link. I've seen this happen many, many times. Worst thing that happens is that you end up buying a new cap that you didn't "need" but the cap is something that should be replaced every 5 years or so anyway. Surprised that a dealer did a $1000 cooling system overhaul and didn't replace a cheap cap.

[Snyperx]

Guess I can try a new cap. I know when I have taken the lid off in the past I always get a hiss of the pressure being released. In my mind that would indicate a good seal, but maybe that is misleading. I am just hoping its not the new pump that was put in going bad already. At least is is covered by the dealer.

My next thing is that the dealer can't get me in until tomorrow morning. Is it even safe to drive? I really don't want to drive it, but don't have access to other transportation.

[DUI Elite]

Originally Posted by Snyperx

Guess I can try a new cap. I know when I have taken the lid off in the past I always get a hiss of the pressure being released. In my mind that would indicate a good seal, but maybe that is misleading. I am just hoping its not the new pump that was put in going bad already. At least is is covered by the dealer.

My next thing is that the dealer can't get me in until tomorrow morning. Is it even safe to drive? I really don't want to drive it, but don't have access to other transportation.

You can have the system pressure tested too. I forget what the actual value is that you want it to be in, but the Bentley manual should say it.

They literally put a "test" expansion cap that has a vacuum hose and pump attached to it on your system instead of the stock one and see if it holds pressure.

If it does, its probably your cap at fault. If not, you have a leak somewhere else in the system.

[CombatNinja]

As long as you have a leak and not complete loss of all coolant, you should be okay to drive. Just keep putting distilled water in it every time you park and it has time to cool off.

[Snyperx]

Going to pick up a new cap and bleed screw for good measure on the way home from work.

[Snyperx]

I replaced the cap last night on the way home from work. When I got back to my place I looked under the hood and saw that the rail and fender were wet again, but not as bad as the initial amount I saw in the morning. I should also mention that when I checked the coolant level after leaving work yesterday the float shot all the way to max even after the boil over (overfill?). In any case I have the dealer checking it over again since they just worked on the cooling system about 2 weeks ago replacing my pump and stat.

All i know is I am freaking out and paranoid about my BMW.

[AlanAZ]

The two indie repairers that my car has been to overfilled my coolant, one of them way overfull. That said, I never had any leakage.

Did you also replace the bleed screw? It could be a combination of being overfilled and a leaking bleed screw. When it's cold you might want to correct the level (I used a large Starbucks straw, and fingertip over the end -- keep what you remove for later top-ups, these engines do go through coolant.)

[Snyperx]

UPDATE: Dealer just called and said that everything tested out good on the coolant system. Pressure was good. SA said it may have been a coolant "burp" from the recent work that was done. I said "Wouldn't that of happened right after the work and not 2 weeks out?" He said "Depends, we have seen it in the past when major work is done to the cooling system."

Guess I'll take his word, they have been pretty good to work with up to this point.

[DUI Elite]

So did they just rebleed the system?

I don't understand what he means by a "burp."

[Snyperx]

Originally Posted by DUI Elite

So did they just rebleed the system?

I don't understand what he means by a "burp."

When I parked my car in the lot yesterday morning, the coolant tank overflowed (burped). I never got a coolant temp message or anything.

[Efthreeoh]

Originally Posted by Snyperx

UPDATE: Dealer just called and said that everything tested out good on the coolant system. Pressure was good. SA said it may have been a coolant "burp" from the recent work that was done. I said "Wouldn't that of happened right after the work and not 2 weeks out?" He said "Depends, we have seen it in the past when major work is done to the cooling system."

Guess I'll take his word, they have been pretty good to work with up to this point.

On the E90, if the coolant bleed procedure is followed properly, there should never be a "burp." The N52 and N54 bleeding procedure is done with the engine cold by cycling the coolant pump with the bleed screw open to let any trapped air out of the system. In cars where the engine needs to run to rotate the coolant pump, air can get trapped in the system, if not bled correctly (most BMWs with mechanical pumps have a coolant bleed screw at the thermostat housing or reservoir anyway). The dealer doesn't know what it is talking about. I'd bet they overfilled the system and the cap is bad because, usually when the coolant pump goes it overheats the system and the expanding coolant goes out the cap through the pressure relief valve. A new cap should fix the problem.

[CombatNinja]

I agree, this sounds like a classic overfill. The new cap should fix your issue with it, now as to the fact that your repair shop can;t seem to perform a coolant bleed properly...

Glad it all seems to have worked out for you. Your cooling system should be good for years now.

[Snyperx]

Well I checked the engine bay again this morning and no coolant, though it has been very cool in the mornings 31F. As I mentioned earlier I did buy a new cap as well as a bleed screw for the reservoir. I hope this is all behind me, it will a nice relief.

[Snyperx]

For the record here is what the tech put on the work order:

[CombatNinja]

LOL at "nooks and crannies" on a work order.

[Efthreeoh]

Originally Posted by Snyperx

For the record here is what the tech put on the work order:

I know this is over with now that you've replaced the cap and bleed screw, but pressure testing the system doesn't include pressure testing the cap. Sure, the system held pressure fine, the cap probably didn't, which is what the problem probably was. That dealer sucks.