Absolutely baffled!

[sprinklerdr]

Absolutely baffled at my 2011 335i cooling issue, 78000 miles. In town, no problem. On the freeway I get about 20 miles and then the yellow and seconds later red overheat display comes up. I've only had her for 6 months and I can't afford to blow it up so I pull over. Five minutes later I start her up and she runs like a champ the rest of the way to work. Oil temp shows cooler, so it would seem all is well at that point. In the last month it's used approximately 1/2 gallon of 50/50 mix. No evidence of a leak I can see, no steam out the exhaust, no issues with how she runs. During the test the fans came on, water pump worked as it was pumping, and I understand the thermostat fails open. It makes heat, so I'm thinking the thermostat is ok. I'm going to do a pressure test tonight, but damn this is maddening!! I have replaced the upper temp sensor, but want to make absolutely sure what's up before I buy a water pump and thermostat that all indications appear to be working.

Any help is welcome and appreciated. Things got tight, so I can't go throwing money at a problem hoping I stumble across the problem along the way.

Thanks!
Be nice, I'm new here. Not a total NOOB, just new here.

[White94RX]

You need to have the fault codes scanned. I can bet there's probably codes stored for the electric water pump. It's probably on its way out.

[Codes2]

+1 on the codes. Don't start swapping parts as an opening move.

I just had to change my water pump at 193000km. She cracked over winter. Small crack. Took a bit to trace. You'll be dropping the sway bar to get access.

[jclausen]

Does the electric cooling fan come at high speed because if it does it's a electric epwater pump problem but certainly check for faluts

[sprinklerdr]

Does the electric cooling fan come at high speed because if it does it's a electric epwater pump problem but certainly check for faluts

I checked the codes, and the ones stored were all ECU codes. Engine overspeed and trans codes. Yay. Nothing for overheat or whatnot. I still haven't done a pressure test yet, but that's tomorrow. I do see some splash by the overflow tank that makes me concerned. Updates tomorrow.

[White94RX]

What does the code say exactly? And what code reader are you using? A generic P-code reader? or a BMW specific scan tool? There is a difference.

[sprinklerdr]

I've been using a Bluetooth Android based reader/datalogger. I did a pressure test and replaced the overflow tank. Now it seems to hover around 220*f. I'm used to 220* being hot, but after searching forums it appears this reading is the norm.
t had codes stored that I cleared. A code for the starter ground/ECU fail reappeared. So it looks like I'm now going to have to chase an electrical gremlin.

[sprinklerdr]

OBD Link MX

[sprinklerdr]

Drove a 45 mile trip at 80mph yesterday, temps were 199-220* and no issues. This morning, with datalogger plugged in, she showed an overheat alarm and the logger showed the gauge pegged. Two minutes earlier it was at 200*. So I pull over, shut the car off, and turned on the accessories to look at the logger again. Showed 210*, so I started the car up and drove the rest of the way with no issue at all. Stupid car.

Is there a second temp sensor that could be failing? Battery reading steady at 14.0 volts.

[White94RX]

So you still have yet to replace the water pump?

It's not a temp sensor failing. Jeez. You've had three guys tell you it's your water pump and you're concerned about a temp sensor. Sounds like you're not getting the answer you want, so you're ignoring it.

[sprinklerdr]

I was hoping it was something simple. I didn't want to spend the money if it was something I could do myself. Seems this is the only thing left. It's funny though, that if it were the water pump or thermostat, that it takes 30 mins for it to "overheat", but immediately cools down (as in shut the car off, look at the datalogger), then it's back to 199-203* the rest of the drive. That's what makes it difficult to spring $1100.

[White94RX]

Well, it's a BMW. They're not cheap cars to maintain and service. Better get used to it.

[sprinklerdr]

And all the German quirks associated. My Benz about put me in the happy house

[doclees]

$300 genuine BMW part. Invest in tools and jacks. $800 of the cost of this job buys a lot of tools. Buy from FCPeuro. Last water pump you ever need to pay for.

[Codes2]

I can't say I don't feel conflicted, based on this observation either.
I'm just following lightly, but could a poor connection cause a misreading of this nature?
Even that doesn't seem likely to me. Power and communication. I don't know, but I'm guessing this is not like an O2 sensor reading resistance or low voltage. Therefore it's less likely a connector issue.
That said, I'd likely disconnect and check it regardless.

I had a new water pump and thermostat installed a few weeks back. Pricey. While it no longer leaks and the temp holds well, I get two codes constantly. Water pump signal () and water pump low power mode(). Try turning on the AC and I get full heat, presumably as it thinks it needs to cool? Whatever. Just glad it's a convertible. When I have time I'll deal, otherwise I'll eventually tire and bring it in.

[sprinklerdr]

Haven't messed with it lately. I drive it in town, no issues even in heavy stop and go traffic in the 90* heat. Drive it on the freeway, 80 mph...all good at 199*+-.....then it'll creep up to 203 and fluctuate back to 195*. Then an all at once peg and limp mode. So I pull over, watch the datalogger until it's out of the red (less than a minute), start the car and drive it another 30 miles with no issue whatsoever. Settles right in at 199* again and is as happy as she can be. Seems to "overheat" after the 20 mile mark. Then it's fine afterward. So no, it's not the radiator, catch tank, line to catch tank, or fans. I bought it used, and unfortunately there's no maintenance record. Yay. My next car is a Honda.

[doclees]

I don't know the 335 but do they have issues with broken head bolts?

[sprinklerdr]

I sure hope not. This car gets deeper in my wallet by the minute. I can do the work, and can afford the parts, but no car worth it's salt is a POS at 79000 miles.

[doclees]

Yes I must remind myself these are the ultimate driving machine.....when they are running. These are sold as performance vehicles and not Subarus. You must expect things to break outside the maintenance schedule.

[sprinklerdr]

Agreed doclees. When they are running. I owdered a WP and thermostat kit. I still don't think that's it though. Reason being I was on the freeway stuck in traffic and it was at 195+-* the almost all of the trip. Then I watched it hit 207* and I said to myself "here we go again". Sure enough, withing ten seconds it pegged and went into limp mode. Stuck in gridlock, I shut the car off. Less than 30 seconds later traffic moved, I started up the car and drove it the rest of the way home, after being in traffic for another 20 minutes with no further issue. Cooled right back down and stayed at 195* the rest of my trip.

[sprinklerdr]

Replaced water pump and thermostat yesterday. Settled in at 228*f and as low as 217* a time or two. Changed ground strap and oil change while I was under the car. Not the hardest thing I've ever done but a solid 8 on the PITA scale.

Will update should things change.

[doclees]

Well?? The antici ........pation ya know.

[sprinklerdr]

Seems to be good. I also learned that 5w30 will throw a bunch of codes and trip the limp mode. Weeellllll alllllrrriiigggghhhtttyyyy thennnnn.
Also decided to check the engine to chassis ground strap. Cashed. Replaced. Like a new car. But wait! In a well conceived notion to forever be in my wallet, the brake pad wear warning screen came on! Oh the joys!

- - - Updated - - -

657186

[doclees]

Yeah that 5w30 throwing codes I'm not buying. If someone can explain that one I'm sure I'd be impressed.

[sprinklerdr]

Dunno why, as the viscosity isn't terribly different. Put in the 0w40 and it hasn't acted up since. Same filter, so it wasn't that. I don't get it either, but that's what's working. Was hard to run 7 quarts of full synthetic into a drain pan.

[doclees]

Coincidence. Either you fixed what was wrong with the water pump change or the codes will come back. I don't know of any sensor sensitive enough to know the difference between oil viscosity.

[sprinklerdr]

Prior to the 335i I had an 06 Benz CLK350 convertible. It was cantankerous, but you could work on it! Prior to that I drove a 2001 Mercury Mountaineer and while it had issues, I put 100k on it reasonably trouble free. I've had the BMW 8 months and in scratching my head as to what I was thinking.

[doclees]

All cars have issues. Learn you car's quirks and head them off. I have a 2004 Range Rover (BMW year's). You hear all kinds of horror stories about Range Rover. Just think of it has higher maintenance. Change things before it breaks if the miles are up there and you want Honda reliability. BMW rubber gaskets leak from 60k to 100k if you are lucky. The RR has the 4.4L. Timing chain guides and changes need changed around 100k. Make friends with FCPeuro. Lifetime warranty on EVERYTHING they sell. Even oil change kits. Cars are money pits. The idea is to keep the pit small.

[sprinklerdr]

Well said Doclees. I'm old enough to know these things about cars and women being money pits.

[doclees]

https://blog.fcpeuro.com/bmw-x5-335i-n54-electric-water-pump-review-failure