new thermostat issue after water pump/tstat replacement?

Chorn519 · 06-14-2023, 09:21 PM

Had my water pump/thermostat replaced by a friend today. Afterwords the code disappeared and the fan wasn’t on full blast at start up so I thought everything was good but on the test drive the fan turned on and the car started heating up like the thermostat wouldn’t open. The top hose is hot going to the engine from the rad but the bottom hose on the passenger side wasn’t hot from coolant flow. Would that be a sign that the new thermostat is stuck closed and not working properly? Any way to know before taking everything apart again and buying another thermostat?

Afam28 · 06-14-2023, 09:25 PM

Maybe try bleeding the system…

JustAnotherSportsCar · 06-15-2023, 06:43 AM

While I am unsure of the coolant flow direction, I do know the N54 thermostat fails open. When you have an open thermostat from startup, it takes a bit longer for the coolant to come up to temperature, and thus longer for your cabin heat to work. If the thermostat is working properly, you should expect one of the main coolant hoses to be warmer than the other, until the system is fully up to temperature. Even then, technically one hose should be cooler because the coolant has just passed through the radiator to dissipate heat. Additionally, a bad thermostat should throw a code and a dash light.

tracer bullet · 06-15-2023, 07:47 AM

Agreed to both of the above and will also suggest to basically relax and be sure what's up. Run the bleed procedure again, or for the first time if you haven't already. Maybe do it twice. And consider whatever your test drive entails - what kind of driving, for how long, what weather you have for the day, and so on.

Bleed it, drive it again, and give some details.

Chorn519 · 06-22-2023, 02:41 AM

Turned out to be a bad new water pump. After some live scans and testing we could tell it was barely on/running. I bought the quickest pump/tstat I could find to get the car fixed quickly and it ended up wasting more time and money doing it twice. After waiting a few days for a new pierburg pump and mahle tstat my 128i is good as new.

So glad I had my vanos filters replaced too. Getting 28.5 mpg highway vs 19-20 mpg before. They were filthy and clogged with crap.

N55e82Simon · 06-22-2023, 11:51 AM

Quote:

Originally Posted by Chorn519

Turned out to be a bad new water pump. After some live scans and testing we could tell it was barely on/running. I bought the quickest pump/tstat I could find to get the car fixed quickly and it ended up wasting more time and money doing it twice. After waiting a few days for a new pierburg pump and mahle tstat my 128i is good as new.

So glad I had my vanos filters replaced too. Getting 28.5 mpg highway vs 19-20 mpg before. They were filthy and clogged with crap.

Sorry you had to do it twice but glad it’s good now. And crazy mpg increase so that’s cool. Basically paying for itself now

Robsbimmer · 07-06-2023, 08:47 PM

I have to replace my water pump, confused about so many brands and prices. Any where from 150 to 700 what would you guys recommend.......I would hate to do the job twice but I'm also on a tight budget.

JustAnotherSportsCar · 07-07-2023, 07:01 AM

I know they are pricey but I went with one from BMW so that I hopefully wouldn’t have to replace again for a long time. That said, I found a BMW dealership selling on eBay and got it slightly cheaper than normal. I think just selling off extra stock.

tracer bullet · 07-07-2023, 07:41 AM

FCP Euro claims a lifetime warranty on parts, maybe check into that. In theory if the replacement fails, you may have to go through the labor again but the part(s) would be covered.

summitp · 07-13-2023, 05:05 PM

Buy the OEM ones. My originals lasted 140k. Why would I use anything else?
Pierburg for the pump, Wahler for the thermostat. FCPeuro has a nice little kit with some coolant and a few new bolts you need.

If no other cooling system maintenance has been done you may also want to replace your coolant hoses (yep, all of em...) your Mickey mouse flange, and your radiator. I also replaced my expansion tank.

Check your new hoses for pinholes. I had a brand new Rein hose from FCP with a pinhole leak. Took me longer to diagnose the leak (only leaked when hot) than it did to swap all hoses and pump and thermostat. Super annoying.

Scott_Tucker · 10-02-2023, 10:29 AM

I just replaced my Wahler thermostat for the second time and both of them are defective. My drive to work is 15 miles and by the time I get to work the coolant is barely 130 degrees. I also made the mistake before of getting the cheap Rockauto pump (I think it was Bosch) and it failed immediately. Even though it says it was a new pump, it had the same failure as the old one so I'm sure it was actually a reman. Plus it looked like it had been bead blasted. And of course right after replacing it I got pulled over and given a fix it ticket because I can't pass smog because the Tstat Map code keeps coming back.

06-14-2023, 09:21 PM	#1
Chorn519 New Member 9 Rep 23 Posts Drives: 2011 BMW 128i Join Date: Dec 2022 Location: Windsor Ontario iTrader: (0) Garage List 2011 bmw 128i [0.00]	new thermostat issue after water pump/tstat replacement? Had my water pump/thermostat replaced by a friend today. Afterwords the code disappeared and the fan wasn’t on full blast at start up so I thought everything was good but on the test drive the fan turned on and the car started heating up like the thermostat wouldn’t open. The top hose is hot going to the engine from the rad but the bottom hose on the passenger side wasn’t hot from coolant flow. Would that be a sign that the new thermostat is stuck closed and not working properly? Any way to know before taking everything apart again and buying another thermostat?
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06-14-2023, 09:25 PM	#2
Afam28 User 298 Rep 775 Posts Drives: 2008 BMW 135i M-sport Join Date: Apr 2018 Location: MD. iTrader: (1)	Maybe try bleeding the system…
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06-15-2023, 06:43 AM	#3
JustAnotherSportsCar Private First Class 83 Rep 114 Posts Drives: 2008 BMW 135i E88 Join Date: Nov 2021 Location: Iowa iTrader: (0)	While I am unsure of the coolant flow direction, I do know the N54 thermostat fails open. When you have an open thermostat from startup, it takes a bit longer for the coolant to come up to temperature, and thus longer for your cabin heat to work. If the thermostat is working properly, you should expect one of the main coolant hoses to be warmer than the other, until the system is fully up to temperature. Even then, technically one hose should be cooler because the coolant has just passed through the radiator to dissipate heat. Additionally, a bad thermostat should throw a code and a dash light.
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06-15-2023, 07:47 AM	#4
tracer bullet Brigadier General 2419 Rep 3,550 Posts Drives: '11 135i , '15 X3 35i Join Date: May 2011 Location: Saint Paul, MN iTrader: (1)	Agreed to both of the above and will also suggest to basically relax and be sure what's up. Run the bleed procedure again, or for the first time if you haven't already. Maybe do it twice. And consider whatever your test drive entails - what kind of driving, for how long, what weather you have for the day, and so on. Bleed it, drive it again, and give some details.
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06-22-2023, 02:41 AM	#5
Chorn519 New Member 9 Rep 23 Posts Drives: 2011 BMW 128i Join Date: Dec 2022 Location: Windsor Ontario iTrader: (0) Garage List 2011 bmw 128i [0.00]	Turned out to be a bad new water pump. After some live scans and testing we could tell it was barely on/running. I bought the quickest pump/tstat I could find to get the car fixed quickly and it ended up wasting more time and money doing it twice. After waiting a few days for a new pierburg pump and mahle tstat my 128i is good as new. So glad I had my vanos filters replaced too. Getting 28.5 mpg highway vs 19-20 mpg before. They were filthy and clogged with crap.
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07-06-2023, 08:47 PM	#7
Robsbimmer New Member 0 Rep 12 Posts Drives: 135i Join Date: Feb 2019 Location: California iTrader: (0)	I have to replace my water pump, confused about so many brands and prices. Any where from 150 to 700 what would you guys recommend.......I would hate to do the job twice but I'm also on a tight budget.
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07-07-2023, 07:01 AM	#8
JustAnotherSportsCar Private First Class 83 Rep 114 Posts Drives: 2008 BMW 135i E88 Join Date: Nov 2021 Location: Iowa iTrader: (0)	I know they are pricey but I went with one from BMW so that I hopefully wouldn’t have to replace again for a long time. That said, I found a BMW dealership selling on eBay and got it slightly cheaper than normal. I think just selling off extra stock. Last edited by JustAnotherSportsCar; 07-07-2023 at 10:17 AM..
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07-07-2023, 07:41 AM	#9
tracer bullet Brigadier General 2419 Rep 3,550 Posts Drives: '11 135i , '15 X3 35i Join Date: May 2011 Location: Saint Paul, MN iTrader: (1)	FCP Euro claims a lifetime warranty on parts, maybe check into that. In theory if the replacement fails, you may have to go through the labor again but the part(s) would be covered.
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07-13-2023, 05:05 PM	#10
summitp Private 213 Rep 74 Posts Drives: 128i 6spd/ 325ic 5spd/ 944 Tur Join Date: Feb 2023 Location: Utah iTrader: (0)	Buy the OEM ones. My originals lasted 140k. Why would I use anything else? Pierburg for the pump, Wahler for the thermostat. FCPeuro has a nice little kit with some coolant and a few new bolts you need. If no other cooling system maintenance has been done you may also want to replace your coolant hoses (yep, all of em...) your Mickey mouse flange, and your radiator. I also replaced my expansion tank. Check your new hoses for pinholes. I had a brand new Rein hose from FCP with a pinhole leak. Took me longer to diagnose the leak (only leaked when hot) than it did to swap all hoses and pump and thermostat. Super annoying.
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10-02-2023, 10:29 AM	#11
Scott_Tucker New Member 2 Rep 8 Posts Drives: 135is Join Date: Mar 2017 Location: Boulder Creek, Ca. iTrader: (0)	I just replaced my Wahler thermostat for the second time and both of them are defective. My drive to work is 15 miles and by the time I get to work the coolant is barely 130 degrees. I also made the mistake before of getting the cheap Rockauto pump (I think it was Bosch) and it failed immediately. Even though it says it was a new pump, it had the same failure as the old one so I'm sure it was actually a reman. Plus it looked like it had been bead blasted. And of course right after replacing it I got pulled over and given a fix it ticket because I can't pass smog because the Tstat Map code keeps coming back.
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