* E46 Cooling Guide (Information w/parts list/bleeding) *

I would add brass bleeder screw, cheap insurance at 10 bucks.

Originally Posted by ddaniel1

I would add brass bleeder screw, cheap insurance at 10 bucks.

Cool mod, and I'd use one if I got it for free. But really unnecessary. OE/OEM plastic replacements are fine. (comes w/ upper hose, IIRC)

Great write up

A bit jealous of those US prices, if I had those prices here I could afford the overhaul every 30k miles

I had to do the cooling overhaul on every BMW I've owned, never replaced the radiator thou as I dont think it poses a danger at the mileage I had my cars with.
I havent heard of a rad failure before 100k miles so I personally dont recommend replacing it any time sooner then that. I was never for preventative maintenance and I still am against it. To me its just money wasted because I know exactly how long the parts can last before replacement. For example , early the water pump failures are usually on prefacelift automatic cars and are due to the fan clutch thats gets the water pump unbalanced. When I bought my current car at 96k miles , I took the water pump out and it slid as ROCK, no side to side play in the bearing whatsoever(pump was stamped '03). I still replaced it with a Stewart EMP because I was planning that anyway regardless of the condition of the old one, but it was quite interesting to see that OE one held so good. On the other side, I had an E39 530i before and only at 65k miles that I bought it with the waterpump was complete TOAST (way too much side to side movement). All E39s have a clutch fan (regardless auto or manual) so I can bet my money that it was the cause.

My current E46 is coming up for a rad replacement this summer, I purposely didnt replace the rad when I did everything else to see how long it would last, but now I think its time , dont feel like waiting anymore.

Another thing I'd like to add, I didnt see it mentioned or simply missed it.

The ET cap on our cars is the very big thing and gets overlooked WAY to many times. ET cap is a pressure valve in our cars, our cooling system is pressurized and runs at 2bar/29psi(on the bottom of the cap it says 200 kpa). Whenever the pressure gets higher the cap releases it (this is why you may see dried up stains of coolant on your ET eventhou its new and NOT leaking). Everyone knows that PRESSURE is the biggest problem , as its what gets our ET to crack. So, the less pressure you have in your cooling system the less chances you have of a failure.

E30s have a 1.4 bar/20psi ET cap (on the bottom it says 140kpa) which when installed on E46 will maintain a lower pressure in your system, thus having less chances of failure. Its a cheap and effective way to be protected.

'91 325i ET cap part # 17111742232

Another way to reduce pressure is to install a high volume water pump. We know that more water flow means less pressure .EMP Stewart is able to pump 20% more water thus reducing the pressure inside the system. How much less pressure??? I dont know, but even if it lowers by 3-5psi its worth it. They offer stainless steel High Flow water pumps that are also lifetime warrantied. This is the reason why I installed one in my car. Its not as cheap as the cap, this one will set you back $170 but in my opinion is well worth the investment

Amazing write up

I myself will be doing my first real mechanical work in the following months.

Cooling system being number one, soon followed by ofhg, vcg, vanos seals. 2002 325, 100k.

Thanks again mango!

Originally Posted by Blocked Out

Great write up

A bit jealous of those US prices, if I had those prices here I could afford the overhaul every 30k miles

I had to do the cooling overhaul on every BMW I've owned, never replaced the radiator thou as I dont think it poses a danger at the mileage I had my cars with.
I havent heard of a rad failure before 100k miles so I personally dont recommend replacing it any time sooner then that. I was never for preventative maintenance and I still am against it. To me its just money wasted because I know exactly how long the parts can last before replacement. For example , early the water pump failures are usually on prefacelift automatic cars and are due to the fan clutch thats gets the water pump unbalanced. When I bought my current car at 96k miles , I took the water pump out and it slid as ROCK, no side to side play in the bearing whatsoever(pump was stamped '03). I still replaced it with a Stewart EMP because I was planning that anyway regardless of the condition of the old one, but it was quite interesting to see that OE one held so good. On the other side, I had an E39 530i before and only at 65k miles that I bought it with the waterpump was complete TOAST (way too much side to side movement). All E39s have a clutch fan (regardless auto or manual) so I can bet my money that it was the cause.

My current E46 is coming up for a rad replacement this summer, I purposely didnt replace the rad when I did everything else to see how long it would last, but now I think its time , dont feel like waiting anymore.

Another thing I'd like to add, I didnt see it mentioned or simply missed it.

The ET cap on our cars is the very big thing and gets overlooked WAY to many times. ET cap is a pressure valve in our cars, our cooling system is pressurized and runs at 2bar/29psi(on the bottom of the cap it says 200 kpa). Whenever the pressure gets higher the cap releases it (this is why you may see dried up stains of coolant on your ET eventhou its new and NOT leaking). Everyone knows that PRESSURE is the biggest problem , as its what gets our ET to crack. So, the less pressure you have in your cooling system the less chances you have of a failure.

E30s have a 1.4 bar/20psi ET cap (on the bottom it says 140kpa) which when installed on E46 will maintain a lower pressure in your system, thus having less chances of failure. Its a cheap and effective way to be protected.

'91 325i ET cap part # 17111742232

Another way to reduce pressure is to install a high volume water pump. We know that more water flow means less pressure .EMP Stewart is able to pump 20% more water thus reducing the pressure inside the system. They offer stainless steel High Flow water pumps that are also lifetime warrantied. This is the reason why I installed one in my car. Its not as cheap as the cap, this one will set you back $170 but in my opinion is well worth the investment

Nice. I thought you were in the US? Your plate looks American-ish. Anyway good info and I agree the radiator usually lasts longer than 100k. But I mentioned that this is just a guide and your mileage may vary.

And the expansion tank cap is listed in the parts list. DODO HEAD!

Please show us your radiator when its out so we have some documentation on E46 radiator failure. I want to know where/how specifically these radiators fail. I know the E36 radiators fail at the neck where the upper hose attaches.

Originally Posted by FenderGuy05

Amazing write up

I myself will be doing my first real mechanical work in the following monthes.

Cooling system being number one, soon followed by ofhg, vcg, vanos seals.

Thank god for these forums, I will save a ton of money on labor!

Thanks again mango!

No problem, FenderGuy05!

Originally Posted by E46Mango

Nice. I thought you were in the US? Your plate looks American-ish. Anyway good info and I agree the radiator usually lasts longer than 100k. But I mentioned that this is just a guide and your mileage may vary.

And the expansion tank cap is listed in the parts list. DODO HEAD!

Please show us your radiator when its out so we have some documentation on E46 radiator failure. I want to know where/how specifically these radiators fail. I know the E36 radiators fail at the neck where the upper hose attaches.

Im in Canada.

Well, I saw the cap was listed but didnt see the info on ability to use E30 cap to reduce pressure.

I wont hold till my rad breaks , been waiting to long and I'll just replace it but I'll upload some pics later of my friends '00 328 auto that just ruptured its rad a week ago so we have some documentation.

Awesome. Good stuff. Wasn't aware we could use the E30 cap. Are you using one? And if so, how long?

Great write up Mango! Should definitely be stickied.

Btw there's a reason the cap is set for 200 kpa. Water under pressure will have a higher boiling point than water at normal atmospheric pressure. If you switch to a 140 kpa cap then you are lowering the efficiency of your cooling system.

Originally Posted by ImolaSix

Great write up Mango! Should definitely be stickied.

Btw there's a reason the cap is set for 200 kpa. Water under pressure will have a higher boiling point than water at normal atmospheric pressure. If you switch to a 140 kpa cap then you are lowering the efficiency of your cooling system.

Thanks! I hope it does. And re: the cap. Thats what I kind of figured. I figured the stock expansion tank cap was designed/specced for its intended usage. Just as the E30 was.

Originally Posted by E46Mango

Thanks! I hope it does. And re: the cap. Thats what I kind of figured. I figured the stock expansion tank cap was designed/specced for its intended usage. Just as the E30 was.

Exactly. BMW used it for a reason. If it wasn't important they would have just used E30 caps to save money.

Originally Posted by E46Mango

Awesome. Good stuff. Wasn't aware we could use the E30 cap. Are you using one? And if so, how long?

I have it for about 20k miles.

Originally Posted by ImolaSix

Great write up Mango! Should definitely be stickied.

Btw there's a reason the cap is set for 200 kpa. Water under pressure will have a higher boiling point than water at normal atmospheric pressure. If you switch to a 140 kpa cap then you are lowering the efficiency of your cooling system.

True but the change isnt drastic to significantly reduce the efficiency but is big enough to reduce the pressure to prolong the life of ET.

Reason why I personally think E30s used a 1.4 bar cap is because back when E30s were made BMW didnt have the technology to make plastics (Expansion tank for the biggest part) withstand the pressure of a modern E46 cooling system which is 2.0 bar. E30s cooling systems are plenty efficient. E46s have a 2.0 bar system due to the fact that technology enables BMW to make ET with the plastic that can withstand the pressure, but as we clearly know E46s ET are cracking open all the time , its THE weakest point in the whole cooling system .

You do lower the boiling point of your cooling system but its still plenty enough to keep the car cool. The change isnt that significant to get scared off.

Its the same when using 50/50 mix of coolant. Its to raise the boiling point and, well mostly to prevent from freezing, but if your country never sees temp below freezing(and also not as hot as texas) you can drive on water only, sure the boiling point will be low but it'll never be significant enough.

Originally Posted by Blocked Out

I have it for about 20k miles.


True but the change isnt drastic to significantly reduce the efficiency but is big enough to reduce the pressure to prolong the life of ET.

Reason why I personally think E30s used a 1.4 bar cap is because back when E30s were made BMW didnt have the technology to make plastics (Expansion tank for the biggest part) withstand the pressure of a modern E46 cooling system which is 2.0 bar. E30s cooling systems are plenty efficient. E46s have a 2.0 bar system due to the fact that technology enables BMW to make ET with the plastic that can withstand the pressure, but as we clearly know E46s ET are cracking open all the time , its THE weakest point in the whole cooling system .

You do lower the boiling point of your cooling system but its still plenty enough to keep the car cool. The change isnt that significant to get scared off.

Its the same when using 50/50 mix of coolant. Its to raise the boiling point and, well mostly to prevent from freezing, but if your country never sees temp below freezing(and also not as hot as texas) you can drive on water only, sure the boiling point will be low but it'll never be significant enough.

Great points. Personally I'll be sticking to the stock cap. But if the E30 cap works for you and provides the benefits you say, then that's great too. The way I see it, I'll be back in there replacing parts anyway at the 75k interval. Expansion tank is just $60 bucks anyway.

Great thread! I agree with the Sticky idea... It will be easier to refer the inevitable cooling system questions here.

Another part I'd consider adding is the fan switch (13621433077, $20.97) and fan switch o-ring (13621743299, $1.32). These mount in the lower radiator hose and are a good idea to replace when replacing the hose as the old o-ring may not fit correctly in the new rad hose.

Originally Posted by 325kev

Great thread! I agree with the Sticky idea... It will be easier to refer the inevitable cooling system questions here.

Another part I'd consider adding is the fan switch (13621433077, $20.97) and fan switch o-ring (13621743299, $1.32). These mount in the lower radiator hose and are a good idea to replace when replacing the hose as the old o-ring may not fit correctly in the new rad hose.

Those are included in my list. The ring comes with the switch. Thanks

Thank you for taking the time to thoroughly put this together (parts, prices, places to buy)!! AMAZING.

Fantastic write up Mango, will definitely use this over the summer as that's when I plan to replace my entire cooling system. Thanks!

Originally Posted by TRIPLE_O

Thank you for taking the time to thoroughly put this together (parts, prices, places to buy)!! AMAZING.

No problem. Believe it or not it actually took me two hours. Halfway into it I was thinking what am I doing

Originally Posted by Cyanide72

Fantastic write up Mango, will definitely use this over the summer as that's when I plan to replace my entire cooling system. Thanks!

No problem. Summer's coming!

I have a question with regard to omissions in the coolant carrying hoses. The two main radiator hoses are always mentioned to replace, but the heater core hoses and hose #5 in the diagram are never included. Come to think about it, I've never seen a mention on more than one e46 board of anyone ever having one of these hoses fail? Anyone?
And if I wanted to prophylactically replace the heater core hoses, are they not connected in impossible to reach locations?
I know the large hoses are under more stress, and smaller hoses can stand up to higher pressures more easily, but eventually all rubber will wear out. I'd like to hear from anyone who has already replaced these as preventative maintenance.
(or otherwise for that matter?)

Stinger, I changed both hoses off of the expansion tank with my coolant refresh, 4 and 5, the other hoses from the heat control valve to heater core looked like they had been changed recently, I saw some rust stains underneath the car so it confirmed a leak there at one time in the past, nothing particularly tricky, the heater core connection was easy to get to when I was doing CCV so I already had the air filter tray removed, the connection under the intake was on there pretty tight but loosened up ok once I got a hold of it. My hoses were pretty spongy and were definitely ready to be changed but I did notice most DIYs don't mention these. I chalked it up to having high mileage.

The brass bleeder screw is a good investment.