[Kenneykickin]

Alright. Back again.

Few days ago got the low coolant light, obviously a leak somewhere as it’s a closed system. Shouldn’t be going low?

Well, drive it for a day after that with the low coolant light on as I was super busy in between appointments, never got the overheat warning or limp.

Went home later that day, parked it. Next day I see a coolant puddle under he vehicle. I top it off, and search for leaks in engine bay while it’s running. Don’t see any. I go ahead and let it idle for about 15 minutes while I vacuumed the front seats out to see if any leaks would occur in engine bay or a weak hose, whatever. Wanted to get it to temp. Well, finish up.. go inside.

Next morning I go out and check the resovoir, it’s empty…

I throw it up on ramps, topped it off again with distilled and took underbody off. It’s a mess underneath but the engine bay spotless so I’m thinking a leak around water pump. Haven’t gotten the best look yet, I also need a oil pan gasket pretty bad as it’s got a nice leak.

Next day I go out and check resovoir, it’s still full??? Yes it’s on ramps on a 2 % incline driveway and no new coolant puddle. I’m confused.

ALSO, When I was topping resovoir off, I noticed my float wouldn’t come up at all? Do they get stuck?

Anyone have any ideas?


Thanks E90 family.

[jwalker87]

There's so much plastic in these cooling systems, it's amazing they operate at all after 15 years! A few thoughts/notes/ideas:

• There are a ton of coolant connections at/near the water pump, so inspecting that area closely with the engine running may help find your leak.
• I have had a leaking water pump before that ONLY leaked when the engine was up to normal temperature - so this could be related to your observations about the reservoir being empty then full. Same thing with a leaky reservoir itself once.
• I have never personally had my reservoir float stick, but it's just a plastic thing that bobs up and down - just give it a poke and it should correct itself. I could easily envision how it could get jammed against the plastic walls if the reservoir goes empty.

And if you tackle the water pump, be sure to do the water pump, aluminum water pump bolts, thermostat, and connecting hose, since those all have to come out anyway.

[StradaRedlands]

Pressure test the system. Luckily you saw a puddle... it's when it leaks down with no puddle that you're in trouble (OFHG leak)!

[Sgop335]

Is there oil in coolant reservoir?

[lobotomy]

Originally Posted by Sgop335

Is there oil in coolant reservoir?

also check for brownish muck inside oil fill cap. Those would be 2 worst case scenarios.
Recently I have been adding coolant to my reservoir with no visible leaks. Later I noticed a slight coolant leak, just drops at a time. The leaking coolant is dripping from bottom of thermostat onto the undercover splash shield. The splash shield collects the pooled coolant, and until that overspills, (like on an incline) all I see is low coolant reservoir, which I am now refilling until I can get to changing out the pump & T-stat. I only found the leak after removing the splash shield while doing a transmission fluid & filter change. Of course, I know it will get worse if ignored. Last thing I want is to have a catastrophic coolant leak failure on the road!

[lobotomy]

Originally Posted by StradaRedlands

...... Luckily you saw a puddle... it's when it leaks down with no puddle that you're in trouble (OFHG leak)!

Very true!
Check to be sure your OFHG is not leaking. Regardless of anything else, If it was leaking on my car, I would attend to it ASAP! (Of course, mine has already leaked like they all do eventually)! Besides a failed OFHG seal oozing oil onto your drive belt, that same seal keeps water & oil jackets separated within the OFH!

[StradaRedlands]

Originally Posted by lobotomy

Very true!
Check to be sure your OFHG is not leaking. Regardless of anything else, If it was leaking on my car, I would attend to it ASAP! (Of course, mine has already leaked like they all do eventually)! Besides a failed OFHG seal oozing oil onto your drive belt, that same seal keeps water & oil jackets separated within the OFH!

Here's a beautifully lit one I did a couple days ago... unbelievably pancaked and cooked to a hard plastic. You can see how much oil leaked out from it. A better than naught chance some coolant contamination as well.

[M-technik-3]

I need to do mine in both my E82 3.0si and the Touring. Toying with doing the N55 but so many bad things happen when pump is not primed properly in Turbo car.

[StradaRedlands]

Originally Posted by M-technik-3

I need to do mine in both my E82 3.0si and the Touring. Toying with doing the N55 but so many bad things happen when pump is not primed properly in Turbo car.

Pretty easy to prime... I did it on our E70 N55. I just pulled the fuse for the fuel pump.

[watchout-everyone]

Originally Posted by Kenneykickin

Alright. Back again.
I throw it up on ramps, topped it off again with distilled and took underbody off. It’s a mess underneath but the engine bay spotless so I’m thinking a leak around water pump. Haven’t gotten the best look yet, I also need a oil pan gasket pretty bad as it’s got a nice leak.

Next day I go out and check resovoir, it’s still full??? Yes it’s on ramps on a 2 % incline driveway and no new coolant puddle. I’m confused.

Thanks E90 family.

I am guessing you topped it at night then you checked for leaking the next morning (without driving). This doesn't prove there isn't a coolant leak


You mentioned about needing an oil pan gasket replacement and the coolant leaking is by water pump. Maybe it's one or both of these hoses needing to be replaced due to melting (from hot leaked oil). It was the case for me

View post on imgur.com

good luck fam

[Kenneykickin]

Thank you for all the knowledgeable replies. Sorry for the late reply myself. Been 5 degrees outside, lol.

I will go ahead and top it off and run it and see if I can pin point this leak. For reference I did the valve cover gasket and OFHG about 10k miles ago and all seems fine there. Did look like there was more of a mess around the water pump / t stat area.