[the_darksyd]

This is a side bar off of my 90k maintenance thread, but I'm trying to understand something and the more I read, the more I get confused and figured this is specific enough not to toss in the middle of the other thread.

#1, I am getting ready to do the coolant flush, so from suggestions and reading I have decided to also do the water pump as it seems like that is the hardest thing to do, and easiest to do while the coolant is out. But as for the thermostat, do I really need to replace it right now? My gauge sits right in the middle and gets there in just a couple of minutes and never fluctuates. I realize that there is a high probability that it will eventually die, but will I really save myself a ton of work and headache by just doing it when I do the pump?

#2, now I've also read a lot about removing the expansion tank (which from reading doesn't excite me all that much), but my question is, what does it actually do? And also, I read another thread where it talked about a transmission thermostat in it. I know it has it's own thermostat, but how is it related to the transmission? And also, why is this one particular item so prone to failure?

Any help is greatly appreciated here, and as far as I can tell, I couldn't find any threads that were dedicated to this discussion, or at least could answer my questions. Thanks!

 

[fcpeuro]

If you are doing the pump, do the thermostat. It is better to just get it all done while the coolant is out of the car.

As for the expansion tank, when coolant heats up, it expanse. The tank gives it room to expand without blowing a hose.

 

[iskoos]

2003 and 90k miles, it would be a good idea to change the expansion tank, water pump, thermostat, belts(if you haven't done it before) and some related parts (look in other threads). Yes, it won't be easy to remove the thermostat.
If automatic, most people change the tranny t-stat as well because they break it while removing the expansion tank. So no question if they should change it or not. If you do not break it, you do not need to replace it in my opinion. It is not one of the items known to go bad. I have been in this forum for several years and I haven't read a single article where it say the tranny t-stat failed and caused a damage.
When I did my coolant overhaul, I was able to save the tranny t-stat and did not change it.
If it is going to worry you so much, then you might as well change it. It is about a $60 part.

 

[the_darksyd]

Thanks for your help everyone.

Is this the tranny thermostat that you are referring to?

Also, my hoses look good, should those be replaced as well though?

 

[iskoos]

Thanks for your help everyone.

Is this the tranny thermostat that you are referring to?

Also, my hoses look good, should those be replaced as well though?

Yes it is the tranny t-stat.
Hoses always look good.
If they haven't been replaced before, do it.
If they have been replaced, then when and how many miles on them?
They are not expesive itmes you know right?

 

[jcourcoul]

American cars get away with not having expansion tanks cause they have an overflow tank where the fluid goes when pushed out as the system pressurizes. Then it has to be sucked back in and that entails a more complex pressure cap. Having a totally sealed system with an expansion tank, IMHO, is a better idea from the engineering viewpoint. The problem is the execution of the idea: using plastic throughout the system for saving weight is good only on the short term but guaranteed to fail on the long run. But by then, warranty will have run out and the car won't be the latest and snazziest model, so it represents no liability to BMW.

Side note: how hard and how recommendable is it to take the radiator out of the car while you're doing the cooling overhaul? In all the DIY's, no mention is made and I can think of at least two good reasons to pull it:

• Fill it partially, vigorously shake it and empty thru the hose openings. Dislodges and removes any deposit in the side tanks.
• Clean the cooling fins with a stiff poly brush, removing dust, dead bugs, etc. Improves airflow and cooling capability.

 

[Tangent]

...My gauge sits right in the middle and gets there in just a couple of minutes and never fluctuates. ...

Our temperature gauges are very buffered. It will point straight up all the way from 167 to 240* F. When my thermostat failed open in April of last year I had no idea until the check engine light came on. In warmer temperatures the light wouldn't even come on, and except for a couple of unusually cold (for SoCal) days the gauge never strayed from dead center.

When comparing the cost of replacing a still-good thermostat with the hassle of rebleeding the cooling system, I recommend doing it all at once.

 

[the_darksyd]

alright...so this is what I'm looking at buying then, all from Bavarian Autosport (I've already got the belts and the fluid):

Thermostat
$67.95

Water Pump and Seal - with upgraded metal impeller
$56.95

Radiator Expansion Tank
$54.95

Expansion Tank Thermostat
$57.95

Bypass Hose - Expansion Tank To Water Pipe
$21.95

Hose - Upper Radiator
$28.95

Hose - Lower Radiator
$26.95

Coolant Temperature Sensor
$23.95

Comes to $339.60...ugh. Which I know isn't awful, but also, not expected.

 

[chitown_bimmer]

Thanks for your help everyone.

Is this the tranny thermostat that you are referring to?

Also, my hoses look good, should those be replaced as well though?

If you are not going to change the trans thermostat be careful when you remove the expansion tank. I had a tough time taking out the tank and broke the trans thermostat when I was finally able to the tank out. The outer body on the piece is plastic as well.

 

[Scott ZHP]

If you are not going to change the trans thermostat be careful when you remove the expansion tank. I had a tough time taking out the tank and broke the trans thermostat when I was finally able to the tank out. The outer body on the piece is plastic as well.

Pretty much everyone breaks it getting it out. At 90k miles, you are way overdue. $350 is cheap insurance for known maintenance issues.

 

[Mo.licious]

Bypass Hose - Expansion Tank To Water Pipe
$21.95

I don't know how many people have replaced this hose (probably not many), when doing the overhaul, but I figure it can't hurt. If you're trying to save cash I'd remove this item from your cart (although it isn't too bad in price).

 

[Rich_Jenkins]

Just a couple "while you are in there" suggestions:

1281738605 Idler Pulley/Roller; Water Pump/Alternator; Offset Mounting
13-62-1-433-077-M9 Coolant Temperature Switch
Adjusting Pulley,11-28-1-748-131-M40
A/C Belt Tensioner, BMW E46 330i, 11-28-7-512-758-M40

E46 seem to be known for squeeling pulley's, I replaced the above ones when I did mine.

The coolant temperature switch is another item I replaced to avoid any problems with worn o-rings on the existing unit.

Also, I didn't know if you ordered a radiator cap, but my tank did not come with one:

17 11 17 42 231 Radiator Cap

 

[the_darksyd]

Went ahead and purchased everything listed above, plus:

Radiator Cap
$11.95

I'm going to try and get through without destroying the thermostat in the expansion tank, but this way I at least have a back up.

 

[iskoos]

Just a couple "while you are in there" suggestions:

1281738605 Idler Pulley/Roller; Water Pump/Alternator; Offset Mounting
13-62-1-433-077-M9 Coolant Temperature Switch
Adjusting Pulley,11-28-1-748-131-M40
A/C Belt Tensioner, BMW E46 330i, 11-28-7-512-758-M40

E46 seem to be known for squeeling pulley's, I replaced the above ones when I did mine.

The coolant temperature switch is another item I replaced to avoid any problems with worn o-rings on the existing unit.

Also, I didn't know if you ordered a radiator cap, but my tank did not come with one:

17 11 17 42 231 Radiator Cap

Coolant temp sensor is already in his list.
It would be a good idea to replace some of the pulleys and tensioners. Most people go that route. I replaced some of them when doing mine.
I do not think you need to replace that by-pass hose. Up to you.
You will need a few more items to complete your list.
One of them is engine bolck drain bolt crush washer. Then you will need O-rings for the tranny heat exchanger.
All those are listed in other related posts. I believe I listed all those part numbers in my thread. Look for "Coolant system Overhaul"

 

[golforcars325i]

Anyone have a part number for the Trans. Thermostat?


Never mind.............. I found it! (17111437362)

 

[3beemers]

Thanks for your help everyone.

Is this the tranny thermostat that you are referring to?

Also, my hoses look good, should those be replaced as well though?

In addition to hoses, fan belts and anything with bearings. You would not want to go back just to replace a noisy one.

Regards

 

[the_darksyd]

Anyone have a part number for the Trans. Thermostat?

The part # for my 2003 330i is 17 11 1 437 362.

 

[the_darksyd]

So crazy update and I guess a good thing I went ahead and ordered everything. On my way home from work yesterday, my service engine light popped on. With all the stuff I've recently done to the car I was a little worried that something got messed up in the process. I checked all the fluid levels and everything looked good, so thought it could possibly be something as simple as the gas cap not being sealed completely. So tonight I ran to an auto store and had them pull the error codes:

P0128 - Coolant Temp Below Thermostat Regulating Temp
P1620 - Manufacturer Control Auxiliary Inputs Auxiliary Outputs

After a little research on here, it looks like the thermostat is on it's way out...good thing I already placed my order, it shipped this morning :thumbup:

 

[golforcars325i]

So crazy update and I guess a good thing I went ahead and ordered everything. On my way home from work yesterday, my service engine light popped on. With all the stuff I've recently done to the car I was a little worried that something got messed up in the process. I checked all the fluid levels and everything looked good, so thought it could possibly be something as simple as the gas cap not being sealed completely. So tonight I ran to an auto store and had them pull the error codes:

P0128 - Coolant Temp Below Thermostat Regulating Temp
P1620 - Manufacturer Control Auxiliary Inputs Auxiliary Outputs

After a little research on here, it looks like the thermostat is on it's way out...good thing I already placed my order, it shipped this morning :thumbup:

I just threw a P0128 myself yesterday. Looks like I'll be following in your footsteps!

 

[golforcars325i]

Darksyd...... did you also order a new Coolant Level Sensor? I believe it fits into the bottom of the Expansion Tank. I was wondering if that's typically replaced as well.