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2Addicts | BMW 2-Series forum Technical Topics N20 (228i) / B46 (230i) Engine, Transmission, Exhaust, Tuning N20 Thermostat housing bolt(s)

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      04-02-2022, 06:54 PM   #1
Uridian
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N20 Thermostat housing bolt(s)

So somehow my water pump housing managed to crack and spray all my coolant on the road. BMW wanted $1400 to replace, so I bought a new pump, thermostat and block thermostat hose flange and dove in.

Well - the 2 T30 bolts holding the thermostat housing to the block are so rusted to bits that one snapped the head off, and one I can't budge since there is no longer a torx head on it, just a rusty donut.

Since this car has an electronic water pump and thermostat, what's the risk if I just cut the head off that one bolt, replace the thermostat and don't bother trying to extract the bolt pieces from the block? Nothing seals to the block besides hoses and and those are fine and secure. If the thermostat just floats, held in place by all the hoses connected to it, is that such a problem?

...and another thing. On the 228, the lower bolts on the water pump are covered by the damn steering rack!! Can barely fit just a bare socket in there, no chance at all a ratchet fits, even with a rube-goldberg extension, wobble, u-joint set up. Ordered some e-torx box wrenches and I hope they fit. What a headache.
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      04-03-2022, 09:23 AM   #2
delvec03
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Thermostat- you'll probably be OK without that one bolt...but it might be worth going at with an easy out and drill bit combo.

Water pump- I found the same issue you did with the steering rack. My plan was to drop the rack and hang it out of the way without disconnecting it electrically. However, i was unable to remove the steering column easily....I left the rack attached with the exception of the passenger side control arms. That took a few larger sockets and wrenches, but it was easy enough to do the job.

I wouldn't recommend trying to do the water pump without dropping at least the passenger side control arms. It's hella tight in there.
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      04-03-2022, 12:33 PM   #3
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I've got an easy out set that I'm going to attempt, but it's possible the outcome here is 2 short lengths of rusty threaded stud sticking out of the block lined up with the thermostat holes. In that case, it might still be ok since nothing needs to seal, right? I could also ghetto it up and jb-weld the inside of the thermostat mounting holes to the "studs" if necessary. Then just sell the car when it's time for another new thermostat, haha!

So far I have gotten 2 of 3 bolts out of the water pump and my E12 box and ratcheting box wrenches arrive today. I really REALLY don't want to drop the rack or mess with suspension this weekend. I have air, so I'm not concerned about wrench sizes, but I don't want to futz with geometry if I don't absolutely have to.
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      04-03-2022, 02:22 PM   #4
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Quote:
Originally Posted by Uridian View Post
I've got an easy out set that I'm going to attempt, but it's possible the outcome here is 2 short lengths of rusty threaded stud sticking out of the block lined up with the thermostat holes. In that case, it might still be ok since nothing needs to seal, right? I could also ghetto it up and jb-weld the inside of the thermostat mounting holes to the "studs" if necessary. Then just sell the car when it's time for another new thermostat, haha!

So far I have gotten 2 of 3 bolts out of the water pump and my E12 box and ratcheting box wrenches arrive today. I really REALLY don't want to drop the rack or mess with suspension this weekend. I have air, so I'm not concerned about wrench sizes, but I don't want to futz with geometry if I don't absolutely have to.
You won't mess with the alignment if you don't touch the control rod adjustment. The steering rack will maintain the same lengths, etc. I'm amazed you've gotten as far as you did!
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      04-03-2022, 03:03 PM   #5
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The ratcheting box wrench just got delivered and did the trick. Got the pump out! It was very slow going - a couple of clicks at a time - but it did come out no problem after it was far enough to finish with my fingers.

So my big obstacle now is the seized thermostat bolts. And... my drill is too long to fit between the engine and the radiator fan.

Because of course.

Thoughts on resting the new thermostat on two little cut off nubs of bolts and calling it a day?
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      04-04-2022, 07:46 AM   #6
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Quote:
Originally Posted by Uridian View Post
The ratcheting box wrench just got delivered and did the trick. Got the pump out! It was very slow going - a couple of clicks at a time - but it did come out no problem after it was far enough to finish with my fingers.

So my big obstacle now is the seized thermostat bolts. And... my drill is too long to fit between the engine and the radiator fan.

Because of course.

Thoughts on resting the new thermostat on two little cut off nubs of bolts and calling it a day?
So ...I'd recommend fastening it down somehow ....even if it's just zip ties. I've had the plastic coolant piping fracture due to heat. Hate to have that happen after taking a bump or pit hole.

You could always drill and tap the rusted bolts....hahaha 🤣🤣
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      04-04-2022, 10:30 AM   #7
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Haha! Upon closer inspection, there does appear to be a fair amount of meat around those holes, so I could drill out and tap larger for an M6 insert.

Well, my shorter drill arrives tomorrow so I guess I'll see where I end up!

The money saved over dropping it at BMW to deal with is dwindling, but at least I've gotten carte blanche from my wife to expand the tool collection!
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      04-04-2022, 10:56 AM   #8
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If you can't get the old bolts out with an easy out, helicoil is a good option for rethreading with the same size. I used that on my belt tensioner after I stripped some threads out.
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      04-09-2022, 11:55 AM   #9
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I have news!

The easy outs got me as far as breaking off the head of the other bolt, leaving me with two threaded studs, but the thermostat housing was still seized on. The metal sleeves in the holes were rusted to the studs. I had to use a pry bar to try and get the thermostat off and it actually pulled the plastic housing right off the sleeves! They were extremely stuck! That actually gave me hope that the threads in the block were fine and it was just the outside that was the problem.

Once I crushed the sleeves off I found rusted, but more or less intact, threads. So I got some M6 nuts and threaded two on to make a lock nut and pretty easily backed the "studs" out of the block!

Success!

Now when I reassemble everything is getting a liberal coating of anti-seize!
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