Thermostat housing stamped 3.1? Which stat do I need?

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euro24

Thermostat housing stamped 3.1? Which stat do I need?

Post by euro24 »

So I've read the threads on here about our cars being equipped with two different t-stat housings: the early one stamped "4.1", and the later one stamped "4.2 A". In my 1985 635 US-spec, I have neither. My thermostat housing is stamped "3.1".

Which thermostat do I need? Also, when I inevitably shear off the housing bolts trying to get them out, what tools do I need to drill them out without harming the housing?
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Post by GripGreg »

Never think you're gonna shear off anything!

Apply PB Blaster or WD-40 or something once a day, a week before the job to allow it to soak in.
Be gentle when removing! #-o It's your car, not the mechanic's car!!
Good luck,,,,Greg
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euro24

Post by euro24 »

GripGreg wrote:Never think you're gonna shear off anything!

Apply PB Blaster or WD-40 or something once a day, a week before the job to allow it to soak in.
Be gentle when removing! #-o It's your car, not the mechanic's car!!
Good luck,,,,Greg
Thanks Greg. Just hoping for the best but planning for the worst.

This weekend I was borrowing my dad's garage while doing a valve adjustment and he was working on his 1969 Landcruiser at the same time. He sheared off every bolt while trying to remove the front grill =D>

Anyways, that still leaves the question: what part no. thermostat do I need?
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Post by GripGreg »

Go to 'realoemBMWparts.com'. Enter your vin & you should be guided to the correct factory stock part?
I use to have problems getting on the site, but not lately.
Continue to use a lubricant. Apply it again! Then later, again! Before you start the job.!

Do you know how to bleed the thermostat? Very, very, very important!!!!

Also, make sure you get the upgraded bleeder valve with the nut, on top of the thermostat housing.
It's easier to work with.
Greg
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Post by ron »

GripGreg wrote: .....WD-40 or something once a day, a week before the job to allow it to soak in.
WD 40 is NOT a penetrating fluid! It is a lubricant and water displacement fluid.
They are ALWAYS rustier than you thought!!!!!!
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Post by jacko »

I agree with Ron. WD-40 has it's uses, but for a penetrating oil, go with something like Kroil or PB Blaster. Spray.....wait..... tap.....spray......wait.....try.
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Post by sansouci »

What about a little heat on the affected area as part of the "lube and pray" technique?
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Post by euro24 »

GripGreg wrote:Go to 'realoemBMWparts.com'. Enter your vin & you should be guided to the correct factory stock part?
I use to have problems getting on the site, but not lately.
Continue to use a lubricant. Apply it again! Then later, again! Before you start the job.!

Do you know how to bleed the thermostat? Very, very, very important!!!!

Also, make sure you get the upgraded bleeder valve with the nut, on top of the thermostat housing.
It's easier to work with.
Greg
By "bleed the thermostat", do you mean the standard "loosen the screw until bubbles stop coming out" routine? If so, yes. If no, enlighten me :)
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Post by GripGreg »

Yes!
And I keep forgetting WD-40 doesn't penetrate; it does so many things. :roll:
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Re: Thermostat housing stamped 3.1? Which stat do I need?

Post by matthewdesigns »

Bringing this one up from the dead as I'm on the same quest.

I also have this elusive housing stamped 3.1. Google searching for that number on a BMW t-stat housing turn up.....this thread and nothing else BMW-specific. Production date on my VIN tag is 11/83. Four years later, anyone have any new thoughts? I don't want to replace this twice if I can help it.

My car has never gotten up to temp in the winter. The t-stat that came out appears to be the wrong temp (71*), potentially damaged, maybe the wrong style, and perhaps installed with the o-ring on the wrong side. The RealOEM part number looks totally different from what came out, but ECS and NAPA both say the RealOEM number is incorrect for my car (read more below). Suffice to say I have no idea what was originally in the car from the factory, and what the 3.1 housing actually requires.

I ordered one from Advance Auto and the Stant 13558 came up for the car, which may not be correct from what I can make out after reading a bunch of threads here. But when I test fit the Stant part in the housing there is about 1cm between the end of the t-stat and the flange inside the housing, which I think I understand is how it is supposed to align. If the pics in this thread weren't missing I may have a little more luck sussing this out.

RealOEM says PN 11531710953 is correct for my VIN, which when searched on the ECS site turns up a part for E30/32/34 that is stated to be incorrect for my car: https://www.ecstuning.com/b-genuine-bmw ... 531710953/ If I enter my year/make/model and search, I get a different part which is said to fit E12/23/24/28: https://www.ecstuning.com/b-genuine-bmw ... 531251041/

Search the same RealOEM number on NAPA, and you get this which is also stated to be incompatible with my car: https://www.napaonline.com/en/p/MRD180472 Put my year/make/model in and search, and I get this https://www.napaonline.com/en/p/MRD180472 which looks like the one ECS says is correct except for the weep hole in the one I just removed. That's another question...do I or don't I need a weep hole in this?

Here's what came out (left) compared to the Stant 13558, which looks like the one ECS and NAPA say is correct when entering the car info, not by searching the OEM number.
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Re: Thermostat housing stamped 3.1? Which stat do I need?

Post by bpoliakoff »

Someone correct me if I am wrong, but my understanding is a weep hole is good and one can be drilled in.
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Re: Thermostat housing stamped 3.1? Which stat do I need?

Post by Brucey »

I looked into this years ago and I think this is what you need to know
…..A further wrinkle on the M30 is the thermostat itself; ~1985 onwards, the housing has an 'A' marking near the joint face and accepts a different thermostat (11 53 1 713 040) than the previous version (11 53 1 254 065). Some earlier engines will likely now also take the later thermostat, since they will have been fitted with the later type (the only housing now available as a spare part) to replace a cracked or corroded original. A late 'stat in an early housing (or vice versa) will cause various forms of poor warm-up and bad running. [edit: if the housing markings are not clear; the later type housing is ~35.5mm deep from the sealing face to the bypass port face; the earlier type is deeper than that by at least 6mm]….
from
viewtopic.php?f=2&t=20916&hilit=thermostat
There used to be some useful photos in this thread but they have been eaten from the bigcoupe server or something.

so

a) 1985 is the changeover year
b) you can measure the depth of the housing and work out which thermostat you need that way (remember an earlier car may be fitted with a later housing)
c) x-ref the BMW part numbers with any pattern thermostat to ensure compatibility
d) note that the dimensions of the thermostat itself are only loosely related to the housing compatibility

On the last point the heater bypass valve is spring-loaded . It has to both close and open, and it isn't always clear that it will do so by looking at it.

Re the weep hole; this slows warm-up slightly but makes the system easier to bleed. More useful than useless or harmful.

Re the sealing; IIRC early versions use the O ring as a cushion and a paper gasket to seal. Later versions use the O ring as both seal and cushion.


cheers
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Re: Thermostat housing stamped 3.1? Which stat do I need?

Post by matthewdesigns »

bpoliakoff, thanks for the notes on the weep hole. I have in the past drilled a hole in thermostats for other vehicles, but this is my first venture into the E24 cooling system and I didn't want to screw anything up!

Brucey, that depth measurement is exactly the nugget of info with which I was hoping someone could chime in...thank you very much! I didn't exactly trust that the A or no-A markings would be an absolute giveaway for which thermostat to use, especially since my housing does not have the typical 4.1 or 4.2 marking as well.
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Re: Thermostat housing stamped 3.1? Which stat do I need?

Post by matthewdesigns »

Alrighty, so I installed the Stant 13558 I had previously purchased, which looked relatively similar to the OEM early t-stat PN 11531254065 that Brucey listed above (but not exactly the same). Which is neither the one that RealOEM says is right, nor the one which comes up as correct on the ECS and NAPA sites ](*,)

The car came up to temp at idle, which it's never done for me, and on a test drive stayed between about 11 o'clock and High Noon, which also has never happened except in the middle of the summer...it's usually down in or just above the blue range to the far left. Gonna drive it for a few days and hope that nothing changes!

Edit: For posterity, I did drill a 2.5mm weep hole in the plate.
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Re: Thermostat housing stamped 3.1? Which stat do I need?

Post by Brucey »

it seems like you have a result! FWIW you should find the fuel consumption a bit improved; the difference would be even greater with a non-cat car.

cheers
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