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Still spewing some coolant...

7K views 20 replies 7 participants last post by  chrischeung 
#1 · (Edited)
Been almost 1000 miles after engine replacement. From very beginning I've been noticing some coolant being spewed out around the intercooler expansion tank.

To make it clear. This only happens when going really highrevs / redline and under load. I can drive around all day long and there will be no signs of it. Need to be pushing the engine for this to happen.

This is the part I'm talking about:

http://www.realoem.com/bmw/showparts.do?model=YA81&mospid=55015&btnr=17_0677&hg=17&fg=05&lang=enUS

It's definitely in the epicentre of the problem but I'm not sure if it's coming from the cap or from a crack in the expansion tank (the SA did a pressure test with over 1 bar pressure and there was no signs of coolant anywhere on the tank).

What I observe , is some coolant accumulated in this small "pit" marked red:



And some drops all over the engine. Here's schematically how the distribution of drops that I usually see , there's also quite a large coolant stain on the inside of the hood of course:

(not the actual engine)


So I'm sure it's not coolant overfill, especially since quite a bit of it has been already "flown" out.
Not sure if it's still a crack in the expansion tank - I don't know if ~ 1 bar pressure test is enough and how much pressure is developed during high revved engine operation (turbocharger operation) ???
The "picture" and the distribution of coolant DOES point to a crack in that "pit" spot as the most likely reason.

Or it's just the cap, which I'm also not sure if it's a pressure cap or just a regular cap that is NOT supposed to let any coolant out. The SA said it's a pressure cap but if you look at the part description in the realoem link above it says "02 Cover lid", and if you look at the main expansion tank cap here:
http://www.realoem.com/bmw/showparts.do?model=YA81&mospid=55015&btnr=17_0615&hg=17&fg=30&lang=en

It says "06 Radiator cap 2,0BAR"

which to me looks like it's the pressure cap and the other one isn't. So it could be the cap - although I can't see how the coolant can be distributed that way if it came from "under" the cap ...

p.s. now that I thought about it looking at the pics I made, it actually could - if you imagine the coolant flying out from the cap area initially forwards and at some point being blown off and backwards since a) the car if moving fast and b) radiator fan blowing it backwards, then the drops would indeed be appearing on the engine cover like that.
 
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#2 ·
Took a 150 mile drive last night on the autobahn with about 100 miles of it over 100mph and probably 50-60 miles constantly on the limiter, accelerating, stretching the muscles, really pushed the engine. The car runs like a on steroids and the limiter is a joke since there's what it feels like room to go up to 200mph.

Anyway, back in the garage, sure enough, there's a wet spot on the inside of the hood, and some coolant drops as described above.

Now, I noted the coolant level the day before that (in the MAIN expansion tank), and it was a bit over "min".
So after the mentioned run, I let the car cool off during the night and this morning checked the coolant level, it was exactly at the "min" level. I topped up probably like 2-3 ounces of water to have the level reach well above "min".

So to me, it looks like the amount spewed out is pretty miniscule - like, after over 2 hours track-like driving on the autobahn, it lost 2-3 ounces of coolant? I mean, it's not the end of the world - maybe it's even "normal" for this car (duh).
Any ideas on what I may be missing?
 
#4 ·
Not sure about anything in this situation, but the hose (I assume you mean the one attached to the expansion tank on the left side) is dry, it does get some of the coolant drops but they're coming from elsewhere.
 
#7 ·
Maybe you already found the answer but I had the same problem and it took my BMW-dealer a while to find out.
One (of 3 I Think) of the lids could only handle 1,2 bar when it should handle 1,5 bar. It was not detected when they did the preasuretest.
 
#8 ·
Not sure how I am the first to post on this but 50-60 miles on the limiter?! Makes me smile from ear to ear to read that. I have only had mine up to 140mph. At the end of the run, I was clocked doing 95 in a 70mph. Was nice to the cop and ticket was for 80. Love driving this car fast, so much fun and so stable!
 
#10 ·
Finally they have found out what was wrong (I hope)! Some of the 750;s (mine included) had their engines replaced. When reconnecting the cooling hoses they connected two of them the wrong way! It has happened in some other cases in the world according to PUMA.
This build up a high pressure and you can’t see from where the coolant is coming.
Now they have reconnected the hoses and I really hope this will make it stop spraying coolant over the engine.
So if you had your engine replace make sure that the cooling system is correctly reconnected. The mistake was difficult to locate since it is hard to see that it was incorrectly connected, the engine runs normal and it is only when you push the engine hard that the coolant leaks.
 
#11 ·
Finally they have found out what was wrong (I hope)! Some of the 750;s (mine included) had their engines replaced. When reconnecting the cooling hoses they connected two of them the wrong way! It has happened in some other cases in the world according to PUMA.
This build up a high pressure and you can't see from where the coolant is coming.
Now they have reconnected the hoses and I really hope this will make it stop spraying coolant over the engine.
So if you had your engine replace make sure that the cooling system is correctly reconnected. The mistake was difficult to locate since it is hard to see that it was incorrectly connected, the engine runs normal and it is only when you push the engine hard that the coolant leaks.
Waiting for the pics from you. Very excited! Can you also ask your SA about the reference number of that PUMA case?
 
#17 ·
Thanks a lot for the update, I am definitely going to visit my dealer
 
#19 ·
GREAT! :thumbup:
I am really glad I could help you. My car has been ok since they swapped the hoses.
My SA said they only found one (1) more incident like this one in Puma in the world! So now I guess there are three! :)
I guess there could be a few more cases since most drivers might not notice it if they don’t rev the engine enough. The previous owner of my car didn’t notice it and the dealer that sold it didn’t find the mistake.
 
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