2008 528i e60.

I had a coolant leak from the front of my engine, 1 drip per second while engine is running = about 1/2 gallon of coolant every 65 miles. I identified the leak to the cylinder head-thermostat hose (part no. 11537545890).

I removed the hose which was clearly cracked but had no O-ring (maybe it eroded over time?). I put on the new OEM part that I got from the local stealership for $55 and started her up. Still leaking from the same area, the underside of the top of the hose where it bolts to the engine.

I take a closer look to inspect and notice that the O-ring (part no. 11537545278) has been pushed out of the bottom creating a void where coolant can easily leak out even though I only tightened these bolts with 8 or so lbs.

I proceed to unbolt and rebolt the hose 3 or 4 times, all leaking, even tried without the O-ring. Is there something I am missing here? I cant find any information online of someone having a similar problem.

Maybe the O-ring on mine was stretched out from sitting on the hose in the warehouse for a few years and is making it not seat properly?

 

I haven't had to mess with that hose myself. But, I'd guess you have some sort of a seating problem. I would be suspicious to think the old O-ring just disappeared or disintegrated. I'd look around for remnants of it - perhaps that is part of the mystery. Doesn't make sense that is is gone. In any case, the O-ring needs to be there. There is some sort of a seating problem if that's where the leak is coming from. Could be the O-ring is crimped, or the metal part it mates to is somehow scratched or corroded or some other way it isn't seating properly.

 

After looking at that hose some more, I think there could be something else to look at. You see there are two bolt holes, but that are on one side of the hose. That would lead me to believe there is a flange that the side without the bolt holes under which the hose fits. Or maybe there is something that bolts over the side of the hose without the bolt holes. Perhaps there is something that is not seated properly in that area.

 

Thank you for the suggestions twh.

I will note that the car had its transmission replaced at 60k and I am not sure if this hose
was disconnected for that repair or any other repair prior to my owning the vehicle. - I only bring this up just in case here is a possibility that the O-ring was never there before I removed the hose. I do all my repairs carefully, and am fairly certain I would have seen the O-ring fall.

From what I can see, I don't think there is any flange, but I will pay more attention for that tonight when I go look again this evening just to be sure. This flange concept was an actual thought of mine, and it seems silly to not have one or a 3rd bolt to equally mount/displace the pressure when bolted.

I went to Advance and bought another O-ring just slightly smaller in diameter, I am also going to try and see if that helps.

 

I'm with twh. That o-ring went somewhere. It is dark in that engine housing, perhaps you weren't able to see the o-ring in the pipe.

 

UPDATE: I bought a smaller but similar size o-ring at the local NAPA and still couldn't get the hose to mount flush to the cylinder head.

Now, at the precipice of frustration, I drive across town in my SO's car to the BMW dealership my cylinder head-thermostat hose o-ring in hand. I give the parts guy the part number for the hose and we pull a new one out and look at the o-ring. And guess what... the o-ring is much smaller than the one that came on the new hose I purchased from that very same dealership only 4 days prior. So, now I'm forced to purchase the proper o-ring from them for another $2.95, oh and now I need another gallon of antifreeze ($25). I get home and put the correct o-ring on the hose in 1 minute flat. Add coolant in another minute.

If only I was given the right part first, I could have saved several hours of my life fighting to properly mount the hose with no dripping.

Scoreboard: Stealership 1, Me 0

I would like to add that my old hose cracked right in the valley of where the o-ring sits on the end of the hose and bolts to the cylinder-head. Even though I was careful while removing the original hose, I guess the original o-ring dropped to the bottom of the engine, that is why I never had the original o-ring to compare the new one to and figure this out earlier.

Thanks for the help guys!

 

Did you have a hard time removing the other end of the hose?










Is there a DIY out there on how to remove this hose?




Thanks in advance!