[jerniganj90]

Hi all,

I'm running around trying to diagnose my e46 325i touring manual with an overheating and disappearing coolant issue. Car has 205,000 miles.

In 2019 around 180,000 miles, I replaced the entire cooling system (hoses, sensors, thermostat, water pump, expansion tank, etc), bar the radiator. Everything was OE or OEM replacement. Car has been super solid since.

Recently at my oil change, the guys said coolant was low but they didn't have any more.
The next day I get some drive through food and pull out hard, revving to like 6k. I look down a mile or two later and my temp gauge is in the red. It was dark and raining so I finished the quarter/half mile back home and turned it off right away.

I've always vigilantly watched the gauge and never seen it move past dead center. I know I was supposed to pull over immediately, and I did so as soon as I could safely.

I refilled coolant and drive a few miles the next day and it overheated again. This time, I shut it off again as soon as I could. It hit the red and I got it towed home.

So, things I've done/noticed:

• Coolant refilled and system bled multiple times.
• Rented a cooling pressure test kit and it held 9psi no problem. No audible leaks or bubbles spotted.
• Unplugged lower radiator fan switch to trigger fan to be on full and it didn't help - still climbed past 110 Celsius
• No coolant in oil (recent oil change was 2 days before first overheat)
• Car will idle in the driveway for 20+ mins but eventually start to overheat. If I drive it, it'll overheat in like a mile or less.
• Seemingly no heat coming out even when engine is warm
• Noticed light white smoke coming from exhaust at idle and when revving, even when warm. Filmed a video of that here. It's hard to see, but you'll notice it for sure. E46 overheating and white smoke

My logical next steps I think are replace water pump and/or thermostat again, but I'm concerned by the white smoke.

Do I have a cracked head?

 

[jerniganj90]

Get one of those kits that detects engine gases in the radiator. That is the best way to answer your question.

Ok will do! Is that something I buy or can I rent from the auto parts store?

With a hot engine at idle, does the top hose feel really hot and the bottom hose cold? If so, then your idea of changing the pump and thermostat would be a good one.

I will give that a go and report back.

 

[jerniganj90]

With a hot engine at idle, does the top hose feel really hot and the bottom hose cold? If so, then your idea of changing the pump and thermostat would be a good one.

The report on the hand temp check is that the upper hose is hot and the lower one is cold.

Does the electric radiator fan run when the engine heats up?

No it does not, that's why I unplugged the sensor just to be sure it worked.

As you know these engines don't take an overheat, even a brief one , very well.

Right now, I think you have an air pocket in the cooling system..keep bleeding...then do the steps above..

Thanks for your help. I have a leak down kit I gotta get back from a friend and then will give that a go.

 

[jerniganj90]

Before you replace any parts you need to test for head failure AND find the source of your leak.. BTW - a pressure test at 9psi does nothing...the M54 cooling system runs at 18-20psi...

I forgot to mention I re-did that test and pushed it up to 18psi. The gauge immediately starts decreasing, but slows as it gets closer to around the 9psi mark, where it will then hold around the 9-10psi mark.

It's hard to say if I'm getting a reliable reading, but I tried it quite a few times and got this same result.

 

[jerniganj90]

Can I drain the system and start over? Will that make the bleeding process easier?

 

[jerniganj90]

No need to drain. Read through this bleeding to understand it, then give it a try.
Post #13 of this thread:

overheating at idle

Today I noticed my temperature gauge going past operating temperature at a drive thru. I started driving and it cooled off. I heard the fan turn on multiple times while driving. I replaced the radiator, thermostat, temperature sensor on lower radiator hose, and also bled the system multiple...

www.e46fanatics.com

Thanks! I will try this asap

 

[jerniganj90]

No need to drain. Read through this bleeding to understand it, then give it a try.
Post #13 of this thread:

overheating at idle

Today I noticed my temperature gauge going past operating temperature at a drive thru. I started driving and it cooled off. I heard the fan turn on multiple times while driving. I replaced the radiator, thermostat, temperature sensor on lower radiator hose, and also bled the system multiple...

www.e46fanatics.com

I followed your instructions closely with no change. No heat and I shut the car off once I saw the temp gauge hit 110.

Ill get my hands on my leak down kit and try that next.

Thanks for everyone’s help so far

 

[jerniganj90]

Wow, just got out the car after my test and discovered some new delicious coolant on the ground. It’s not a constant leak but it’s a decent bit of it.

Did maybe my radiator pop? It’s coming from the drivers side near the expansion tank, but there’s drips of fluid all over the place under the car. It’s on the sway bar, the expansion tank has stuff all over the side. Cant quite narrow it down.

 

[jerniganj90]

Ok, got a bit more info to add here. I think I've narrowed it down to head gasket or cracked head.

Pulled the plugs and this is what they looked like. All plugs and coil packs were replaced less than 2,000 miles ago in September.
It's cyl 1 from left to cyl 6 on right.
Note the cylinder 3 plug is a lot cleaner looking.

I ran a leak down test today and most cylinders have a little bit of air leaking from the oil cap.
Cylinder 2 leaks a ton of air into cylinder 3. My gauge isn't reading properly, so I don't know percentage but it is very audibly leaking and you can feel it clearly.
I double, triple checked I was on the correct stroke.

This is why I think the condition of spark plug 3 is noteworthy. Is the head gasket bad between those cylinders there and there's mixing between the two cylinders?

The other thing I failed to mention in the original post as it didn't seem relevant at the time was that I had a misfire code a few months ago.
It was in late September and it was resolved by replacing all the coil packs and spark plugs. (done less than 2000 miles ago as previously mentioned).

Was this possibly related or just coincidence?

 

[jerniganj90]

This is the big problem: with #2 valves all closed, the only way to leak into #3 is through the head gasket,

That’s what I thought.

This motor has over 200,000 miles on it so I think I’m going to start looking for a b30

 

[jerniganj90]

Just wanted to post a follow up that the mystery has been solved.

I tore into the engine and found the water pump destroyed. I ordered this from FCP Euro in April 2019 and I put maybe 30,000 miles on it since then.
Kinda crazy this plastic impeller version failed like this.

I'll be ordering the metal version from EMP Stewart despite the lifetime replacement from FCP.

Thanks everyone for your help.

 

[jerniganj90]

what brand was the water pump that failed?

The failed water pump does not explain the loss of coolant and apparent coolant in cylinders..

Saleri.

Yeah it pretty much does since the water pump failed and the car overheated. Probably warped the head and/or blew the head gasket, so it was burning coolant. One of the first things I mentioned was that I could see white smoke in the exhaust, so I think this is the root cause of all the issues I encountered