[Djrides16]

I've got a 2006 BMW 325xi. I had an intermittent coolant leak. Coolant would blow out the reservoir from the cap. When coolant got low I would get an overheating warning. This would happen once every week or two. It happened while the ambient temp was 80°+ I thought initially it was related to the ambient temp as it wasn't happening after the weather cooled off a bit. It was fine for about 2 months and then I checked the coolant level as it had been a bit since I'd done that. The coolant level was good but the next day I had the same issue again and it got progressively worse over the next 2 weeks to the point where I had to add coolant twice in one day after only driving about 20 miles each way to work and home. Sounds like a classic head gasket symptom but I know this water pump, t-stat, temp sensor system doesn't operate conventionally. I did check all my wires to my water pump and t-stat for continuity and they all checked out. My water pump runs the bleed procedure so it's working and I had replaced it and the t-stat about 7 months before this was an issue. It's a Rein t-stat and SKP water pump. Any thoughts on what to look at? I'm a mechanic but don't really see these cars at work so I'm not super familiar with them. My gut says head gasket but I ran across some other forums saying it could be an electrical thing and I'm not super clear on the operating strategies for the cooling system so I don't know where to go with this. Any help is appreciated!

[Bmw1939]

Oh Lord. Drain the oil and look for signs of water contaminated oil. Drain the coolant and look for signs of oil contaminated water. If none, refill both and replace the cap and pray while monitoring for leaks and coolant temp. Never ever drive a car when it is overheating. You could not only blow a gasket but crack the block.

[Djrides16]

Originally Posted by Bmw1939

Oh Lord. Drain the oil and look for signs of water contaminated oil. Drain the coolant and look for signs of oil contaminated water. If none, refill both and replace the cap and pray while monitoring for leaks and coolant temp. Never ever drive a car when it is overheating. You could not only blow a gasket but crack the block.

Haven't seen any signs if contaminated fluids. Always pulled over when it overheats. I can top off the coolant after it's cooled enough to get the cap off and then it's no problem for a little bit.

[TriumphTim]

I would try to very carefully inspect all the coolant hoses and connections.

I replaced all mine and still had a problem with the new mickey mouse front flange failing after a year or two, went the aluminum flange. The small hose across the top of the radiator gets brittle too.

I think I recently had a defective coolant tank cap too. Do you have a pressure tester at work?

I have read that head gaskets are rare for these engines and I know the plastic cooling system really does suck, I would keep looking there.

[Djrides16]

Originally Posted by TriumphTim

I would try to very carefully inspect all the coolant hoses and connections.

I replaced all mine and still had a problem with the new mickey mouse front flange failing after a year or two, went the aluminum flange. The small hose across the top of the radiator gets brittle too.

I think I recently had a defective coolant tank cap too. Do you have a pressure tester at work?

I have read that head gaskets are rare for these engines and I know the plastic cooling system really does suck, I would keep looking there.

It's definitely leaking at the cap. It's very obvious. I have replaced the reservoir and cap.

[e90yyc]

What’s your coolant temp during normal operation? (Pull up hidden menu in BC; instructions online.)

Is the bump on the coolant level float flush with opening on tank or is the float fully extended?

[Djrides16]

Originally Posted by e90yyc

What’s your coolant temp during normal operation? (Pull up hidden menu in BC; instructions online.)

Is the bump on the coolant level float flush with opening on tank or is the float fully extended?

The bump is flush with the top of the reservoir when I top it off. I'll have to check operating temp tonight

[ctuna]

I think I saw that coolant also runs through the OFG and that is a lot
easier a fix than a Head Gasket.

[Djrides16]

Originally Posted by ctuna

I think I saw that coolant also runs through the OFG and that is a lot
easier a fix than a Head Gasket.

https://www.youtube.com/watch?v=ZJmy6OzfeDg

Yep, I replaced that at the same time as the water pump

[Bmw1939]

So what's the diagnosis? I don't have social media... This is my entertainment.

[Bmw1939]

What happened?

[Djrides16]

Well, after pulling the wiring harness out to inspect it like I read about in some other threads the car does not start and sets mot DTCs. Haven't had time to dig into that and figure out what I forgot to plug back in

[Serf27]

Do you see any leaks?
I don’t think I saw any mention of that.

[PichaDis11]

It's time to check the codes with a scanner that's can read BMW fault codes. If you're having electrical issues then that's a good place to start.

[Djrides16]

Originally Posted by PichaDis11

It's time to check the codes with a scanner that's can read BMW fault codes. If you're having electrical issues then that's a good place to start.

Yeah I have a scanner I just haven't had time. I've been working on other projects