[rusty_sojah]

i got Cobb down pipes installed last weekend and have been driving the car a little harder than i used to for the past couple days. yesterday afternoon sitting in traffic the temp warning light came on (1st time ever for me in 10 months of ownership) and luckily i was like 4 mins away from home. checked the coolant level this morning and it was a little low (the measuring stick was still floating, but just barely) so i filled to the max fill line. I tried not to overfill but i might have by a little.

way home this afternoon sitting in 82 ish degree stop and go traffic light comes back on like 2 mins away from my parking garage so I notice it is in sort of a slow limp mode (and AC stopped blowing cold for a minute or so) but i make it into the parking garage. i opened the hood and as i did it seems like the cap of the coolant reservoir either blew or unscrewed itself to release a ton of steam and fresh coolant.

i don't see any errors in my Cobb accessport tuner thing besides 4 that seem associated with the down pipes (even though the website claimed there wouldn't be any errors)

P0420, P0430
P29F4, P29F5

I guess no way to be sure, but before i drop $450 on a water pump thermo kit is there any other likely suspects?

car is a 2011 335is but only 33600 miles.

BTW i am waiting for the engine to cool down before i go inspect further if any hoses blew, but the geyser appeared to be coming right out of the cap or side of the coolant fill cap. i also noticed this morning that my cap was a little loose, like the first spin was really easy then it had some resistance. But this wouldn't cause the car to overheat, especially after it was filled up all the way this morning i don't think.

if you have any intelligent thoughts or comments, please do so

[rusty_sojah]

Well coolant expansion tank wouldn't hold pressure, so that was replaced. Hopefully that fixes everything.

[Emilime75]

What do you mean, exactly? Was the cap tested and found that it wouldn't hold pressure? Or was the cooling system pressure tested and you found a damaged/cracked tank?

[rusty_sojah]

Originally Posted by Emilime75

What do you mean, exactly? Was the cap tested and found that it wouldn't hold pressure? Or was the cooling system pressure tested and you found a damaged/cracked tank?

What do u mean, what do i mean ... yes the system was pressure tested and the tank reservoir had a small crack and would not hold pressure.

[Emilime75]

Seriously? The correct way to word it would've been to say that the expansion tank had a crack. The cap is designed to hold a certain amount of pressure, then release, so when you word it the way you did...

[rusty_sojah]

Originally Posted by Emilime75

Seriously? The correct way to word it would've been to say that the expansion tank had a crack. The cap is designed to hold a certain amount of pressure, then release, so when you word it the way you did...

Maybe we are talking about different things not a big deal and also not trying to argue. The 1st poat and second post were like 1.5 days apart so further in the troubleshooting and further in the story.

The hairline crack was actually just under the cap so when the geyser of coolant was spewing out it appeared to be coming from the cap but i didn't find out there was a crack and that it wouldn't hold pressure until it was tested the following day by a shop.

I know my writing style is confusing. Believe me i write how i talk and i also talk the same way. Sorry for the long explanation. And i appreciate all insight.

[Jaronbwall]

Did you end up replacing the water pump + thermostat?

[OTO335i]

Originally Posted by Jaronbwall

Did you end up replacing the water pump + thermostat?

Read post #2....

[rusty_sojah]

Jaronbwall,

No, and hopefully i don't have to. Today will be the first full day i drive it since the coolant tank replacement and getting a thumbs up from an independent bmw mechanic

I sure hope this is the last update on this thread from me, at least for a while, wish me luck...

[rusty_sojah]

Well more overheating issues and still no codes related.

Dropping back off at the shop for more troubleshooting. They said the water pump was working but mayne the fan or thermostat is a culprit.

[Jaronbwall]

Damn dude that's annoying. I had "shadow codes" or what ever when my pump went out. I bought the parts on https://www.turnermotorsport.com/
Replaced everything in about 3-4hrs and tasted coolant for the first time.

Mine went out 94k miles and full throttle was like 45mph. I was so confused lol

[rusty_sojah]

The shop called me back yesterday and said that my cooling fan (the one that attaches to the radiator) comes on at first (duh), but somehow shuts off after a couple of minutes. I did notice that it was only heating up when i was stopped and told them to check out the fan, but they did find that it was stopping.

The shop wants 1500 to replace with a new one. i said no. my friend is going to hook me up with a used one tomorrow and i will see if this fixes my issues,, fingers crossed...

[RSL]

Fan can start from residual heat on a warm start and then slow or stop shortly after depending on conditions. What they observed isn't remotely definitive. There are a lot of conditions for the fan, it's not even close to running 24/7, especially in cooler weather, but probably does run mostly when the A/C is on. You want to verify if the fan is coming on at all or when it should (A/C on at temp, over temp, test with INPA/ISTA) or not before doing anything.

Double check that the fan harness is fully seated/clicked in though. If the fan is not coming on at all, still doesn't mean the problem is the fan itself. It could be the relay, wires or any number of things, but don't just start throwing money/parts/time at it without even knowing for sure that the fan doesn't work. Since it did spin at some point, doubt the fan itself is the problem.

[rusty_sojah]

Originally Posted by RSL

Fan can start from residual heat on a warm start and then slow or stop shortly after depending on conditions. What they observed isn't remotely definitive. There are a lot of conditions for the fan, it's not even close to running 24/7, especially in cooler weather, but probably does run mostly when the A/C is on. You want to verify if the fan is coming on at all or when it should (A/C on at temp, over temp, test with INPA/ISTA) or not before doing anything.

Double check that the fan harness is fully seated/clicked in though. If the fan is not coming on at all, still doesn't mean the problem is the fan itself. It could be the relay, wires or any number of things, but don't just start throwing money/parts/time at it without even knowing for sure that the fan doesn't work. Since it did spin at some point, doubt the fan itself is the problem.

When i got it home earlier today and turned off then back on the fan wouldn't come on at all. I let it sit for like 20 mins then went back and started the car again and the fan didn't come on at all. But i had the clumate control off completely. I normally drive with it completely off for the last few months since it is winter in Hawaii and about 72-82 every day.

[rusty_sojah]

When should the fan come on?

[RSL]

Certainly before it overheats, but a lot of things are tied into the cooling system so not sure of anything one particular thing to force it on except maybe INPA/ISTA to manually set fan duty cycle for testing and A/C on should do it, but might need to be at temp. You could also remap the fan duty cycle over temp diff in XDF if you're not on a locked tune.

About 70F here today, fan stayed completely off even at operating temp until I kicked on the A/C and then it ran about 15%.

[rusty_sojah]

Originally Posted by RSL

Certainly before it overheats, but a lot of things are tied into the cooling system so not sure of anything one particular thing to force it on except maybe INPA/ISTA to manually set fan duty cycle for testing and A/C on should do it, but might need to be at temp. You could also remap the fan duty cycle over temp diff in XDF if you're not on a locked tune.

About 70F here today, fan stayed completely off even at operating temp until I kicked on the A/C and then it ran about 15%.

well i just drove the car into work (morning commute) and ran the AC the entire way. It was a little chilly in the car, but amazingly the fan was on when i reached my work parking lot.

Still going to replace the fan this afternoon but I guess i will keep the AC running the entire drive to my buddy's house for the part swap. As much as i don't mind always driving around with the AC on if this is the ultimate fix, i would prefer not to have to.

[RSL]

Running A/C constantly isn't the fix, but does verify that the fan is operating, so swapping fans is not likely to resolve anything. You can adjust the climate control temp to be comfortable, just make sure the compressor is on.

I assume the system was pressure tested after replacing the tank to make sure that was the only leak, but that may be assuming too much. If the cooling system bleed procedure wasn't done after replacing the tank, I'd do that next. If you're not sure it was done, I'd just do it anyway. You'll want a battery charger connected for it.

[rusty_sojah]

Originally Posted by RSL

Running A/C constantly isn't the fix, but does verify that the fan is operating, so swapping fans is not likely to resolve anything. You can adjust the climate control temp to be comfortable, just make sure the compressor is on.

I assume the system was pressure tested after replacing the tank to make sure that was the only leak, but that may be assuming too much. If the cooling system bleed procedure wasn't done after replacing the tank, I'd do that next. If you're not sure it was done, I'd just do it anyway. You'll want a battery charger connected for it.

the shop told me they did the proper bleed and fill and that the pressure was good after the coolant tank replacement. they charged me for another hour of troubleshooting which they said they reconfirmed the water pump was functioning properly, the thermostat is opening and closing appropriately, and that the fan was shutting off when it shouldn't.

i agree that replacing the fan may not solve the issue but at this point for 20 bucks it is my next step in troubleshooting. if it fixes it then i'm only out $20 and a bottle of this rum i picked up for the dude. if it is still not working correctly and shutting off unexpectedly with the other fan then at least i didn't shell out 1500 to that shop, or 650 to ECS (for the part) and a DIY.

if this doesn't fix the issue then i really don't know what to check or replace next, any other recommended things to check for? and thank you for all the help.

[RSL]

At least that's cheap. I'd pull the cap and verify the level again and maybe bleed it again anyway.

I'd log everything to see what it was all doing while driving (all temps, water pump, thermostat, fan) at what temps, particularly if it gets to the point of overheating again.

If the fan is still in question by them even though it seems to be working, I'd change the fan duty cycle to 50-100% via XDF for all temp difference points if you have MHD. It will run faster where it would normally be slow and you'd hear it without logging or popping the hood. If the fan doesn't work with the A/C off for some reason, not sure what the next step is honestly, maybe ISTA test procedures. We know the fan unit works, so at that point might be other monitors/sensors.

[rusty_sojah]

So i swapped out an identicle fan, also used, and it sid the same thing. My buddies roomie was walking by i explained the whole citiation to him, he said to check the fuse relay switch. He pulled a wire out of his pocket (kinda weird) and jumpered the switch relay box and the fan started right up. He left it wired up and it works for now but i guess i just need a new relay switch, fan is fine.

[JuniorB]

Leaving direct power like that will burn the relay out in time. What he did was a direct power to fan. The fan relay powers the fan from a different source when needed. Your temp sensor can be the culprit, as once it reaches temp it, it sends signal to DME to activate the fan. Something in this series is the issue, if the relay is a no go, look into a bad sensor.