[igell]

So recently got the P0128 code on the 07 335i (Bad thermostat)
Also still on the original water pump (currently at 80k)

Over the last 6 months or so I also noticed that I get low coolant warning every couple of month. No other symptoms.
1. could the occasional low coolant be an indicator of a bad pump?
2. how likely is the pump to go out at the same time as the thermostat?

Looking for some advice... should i go ahead and replace water pump at the same time as the thermostat? I'll save myself a couple of hundred dollars in labor overall... but its about $600 price difference w parts.
or
risk it and do just the thermostat now and hope the pump lasts.

[Jacblack]

Yes save yourself the headache and replace the pump at the same exact time. Usually one is behind the other in failure.

[BashShah]

Replace them ASAP.

[jon_335]

Replace both at the same time. You don't want to have to go back in there later. If I'm not mistaken, the water pump has to come out to get to the thermostat. Or if nothing else, makes it a lot easier to get at.

[BMW_drei]

Originally Posted by jon_335

Replace both at the same time. You don't want to have to go back in there later. If I'm not mistaken, the water pump has to come out to get to the thermostat. Or if nothing else, makes it a lot easier to get at.

This.

If the tstat or wp aren't leaking, you will also have a coolant leak somewhere that needs to be fixed.

[jon_335]

You also could have a cracked flange in one of the coolant hoses. I replaced my wp and t-stat last month. A day after the repair, I was left stranded because I had a catastrophic failure of the hose that connects the oil cooler to the t-stat. And 2 days later the plastic flange on the upper radiator hose let go and almost left me stranded. Wish I would have known about those damaged hoses first because I could have replaced them when I did the wp. Instead I ended up paying a shop to diagnose and repair.

[igell]

so there are 4 hoses there.. do you recommend to replace all 4 when the work is being done?

[jon_335]

I replaced the U shaped hose between the t-stat and wp when I was in there ... figured might as well since it gets removed anyway. I wish I had replaced the others. The upper radiator hose looks to be fairly simple. And the hose from the t-stat to the oil cooler doesn't look too evil. If you do replace it, be sure to order the o-ring. I did my OFHG the same weekend and pulling that hose would have made life a little easier. The lower radiator hose looks to be a bitch, but I don't know for sure.

Your call if you want to replace the hoses or not. When I did my research, I didn't see many people suggesting to replace those hoses. And the guy in the BavAuto water pump video suggested NOT replacing the hoses. Maybe I was one of the unlucky ones? Also, replacing all of the hoses can add a bit of money to the project.

[igell]

well .. ended up replacing upper and lower rad hoses as well which cost $75 a piece :/