Thermostat Housing Leak

Jagaer · 12-17-2020, 11:22 AM

Just under 160k kms on my E91 (N52), have not replaced the pump or thermostat. (Have both on-hand, as I expected them to go out)

It appears that the Thermostat Housing is Leaking. But before I dive in and replace the thermostat and pump, I wanted to ask for a second opinion from those that have already replaced theirs once - Just to make sure that it is in fact the Thermostat Housing and not one of the hoses (since I don't have all the hoses on-hand)

It appears to be a slow leak, so I think I've got a few days before it becomes an urgency, in case I do need to order a few more hoses etc...

moantreal · 12-28-2020, 09:06 AM

I recently did my thermostat and waterpump. After replacing them I still had coolant leaks from two of the hoses that connect to the thermostat. Those plastic connectors warp overtime and need to be replaced as they wont seat properly. I ended up having to replace the lower radiator to t-stat hose as well as the lower coolant tank hose cause it connects to the t-stat as well. Better safe then sorry. Order those hoses!

Jagaer · 12-28-2020, 05:57 PM

moantreal Thanks for the tip on the hoses, I'll take a look at them while I'm in there.

I believe the source of the leak is a cracked thermostat - Maybe the bolt expanded as it rusted, cracking the housing and creating a slow leak.

As an aside, the job isn't too difficult. It just takes a lot more time in the winter...(Garage is insulated but not heated, so it was only 3C in there... had to take a number of breaks since I kept getting my hands wet/cold with coolant)

12-17-2020, 11:22 AM	#1
Jagaer Private First Class 430 Rep 170 Posts Drives: 2011 E91 328xi 6MT Join Date: Aug 2017 Location: Kingston, Ont iTrader: (0)	Thermostat Housing Leak Just under 160k kms on my E91 (N52), have not replaced the pump or thermostat. (Have both on-hand, as I expected them to go out) It appears that the Thermostat Housing is Leaking. But before I dive in and replace the thermostat and pump, I wanted to ask for a second opinion from those that have already replaced theirs once - Just to make sure that it is in fact the Thermostat Housing and not one of the hoses (since I don't have all the hoses on-hand) It appears to be a slow leak, so I think I've got a few days before it becomes an urgency, in case I do need to order a few more hoses etc...
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12-28-2020, 09:06 AM	#2
moantreal New Member 2 Rep 5 Posts Drives: E93 335i Join Date: Dec 2020 Location: Charlotte, NC iTrader: (0)	I recently did my thermostat and waterpump. After replacing them I still had coolant leaks from two of the hoses that connect to the thermostat. Those plastic connectors warp overtime and need to be replaced as they wont seat properly. I ended up having to replace the lower radiator to t-stat hose as well as the lower coolant tank hose cause it connects to the t-stat as well. Better safe then sorry. Order those hoses!
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12-28-2020, 05:57 PM	#3
Jagaer Private First Class 430 Rep 170 Posts Drives: 2011 E91 328xi 6MT Join Date: Aug 2017 Location: Kingston, Ont iTrader: (0)	moantreal Thanks for the tip on the hoses, I'll take a look at them while I'm in there. I believe the source of the leak is a cracked thermostat - Maybe the bolt expanded as it rusted, cracking the housing and creating a slow leak. As an aside, the job isn't too difficult. It just takes a lot more time in the winter...(Garage is insulated but not heated, so it was only 3C in there... had to take a number of breaks since I kept getting my hands wet/cold with coolant)
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