[jimmyjames408]

i did some searching and was surprised to find out my 335i has a timing chain instead of a belt.

but what i'm not sure of is the water pump. on my family's s500 w/ a timing chain, the water pump isn't changed until it starts making noise/fails.

is that the same for bmw's? or do i have to change it at 60k?

[kevin@bavarianx]

I would change the water pump by 60k along with the thermostat. That is one of the weak points in all BMW cooling systems. It is better to be safe than sorry with preventative maintenance.

[ENINTY]

The water pump is electric and not driven by the engine belt system. The thermostat is separate from the engine block (it's actually mounted to the water pump). Being that the water pump is electrically driven, the failure of it is more related to production anomalities rather than wear. Waterpumps that are belt driven usually fail because the lateral pressure the belt exerts on the pump shaft eventually wear the seals and then bearings. Because the E90 water pump has no belt pressure as mentioned it will not fail for that reason. The only problem with this design is that you can't tell when the pump is starting to fail. Belt driven pumps have a weephole in them which provides indication that the inner shaft seal is starting to fail because it will allow a small amount of coolant to leak out for detection. If the E90 waterpump fails, it will show an engine overheating warning indictor in the gauges.

The thermostat fails open, so it won't overheat the engine if it does fail. Also, the thermostat operation is monitored by the OBDII system, and if not operating properly will trigger the "service engine soon" light.

You should replace either one when they fail. They are not a "preventative maintenance" item.

[Chriztofor]

Read this, some last a long time, some others not so long. YMMV. http://www.e90post.com/forums/showth...er+pump&page=2

By the way, someone mentioned changing the timing belt if applicable. Well, it is not applicable for our cars. We have a chain and not a belt and NEVER heard of the chain failing even on cars with over 200,000 miles.

[ENINTY]

So there is confusion going on here and in the other post cited. The OP is confusing different engine designs. A lot of Japanese cars and a lot of older European cars have an engine design using a toothed-rubber timing belt to drive the camshaft. Usually, this type of engine design utilizes the timing belt as mechanism to also drive the waterpump. Because waterpumps driven by belts tend to wear out over time, and because rubber timing belts, like all other engine drive belts, require replacement on a schedule as a preventative maintenance item, the best practice (and recommended by most manufacturers) is to replace the waterpump at the same interval as the timing belt. The concept being that since you are in that part of the engine changing the belt, it is economical sense to just replace the waterpump at the same time so as to prevent from going back in to just replace a failed waterpump at a later date. Timing belt driven water pumps are relatively inexpensive ($40 - $60) so the added cost to the job is minimal as compared to the labor to replace the waterpump at a later date.

The N52/54 design with a timing chain and electric water pump alleviate the need for replacement of the waterpump as it is not driven by the camshaft drive mechanism. The N52/54 waterpump is a $500 part and the Thermostat is a $120 part (not counting discounts), and obviously are not considered preventative maintenance items.

[NaTuReB0Y]

my car overheated.....at around 60k

bought the waterpump & thermostat at 20% discount....

had neighbor installed for $200.....

[Chriztofor]

Originally Posted by NaTuReB0Y

my car overheated.....at around 60k

bought the waterpump & thermostat at 20% discount....

had neighbor installed for $200.....

Curious, did you ever change the coolant before the water-pump failed?

[jimmyjames408]

Originally Posted by ENINTY

So there is confusion going on here and in the other post cited. The OP is confusing different engine designs. A lot of Japanese cars and a lot of older European cars have an engine design using a toothed-rubber timing belt to drive the camshaft. Usually, this type of engine design utilizes the timing belt as mechanism to also drive the waterpump. Because waterpumps driven by belts tend to wear out over time, and because rubber timing belts, like all other engine drive belts, require replacement on a schedule as a preventative maintenance item, the best practice (and recommended by most manufacturers) is to replace the waterpump at the same interval as the timing belt. The concept being that since you are in that part of the engine changing the belt, it is economical sense to just replace the waterpump at the same time so as to prevent from going back in to just replace a failed waterpump at a later date. Timing belt driven water pumps are relatively inexpensive ($40 - $60) so the added cost to the job is minimal as compared to the labor to replace the waterpump at a later date.

The N52/54 design with a timing chain and electric water pump alleviate the need for replacement of the waterpump as it is not driven by the camshaft drive mechanism. The N52/54 waterpump is a $500 part and the Thermostat is a $120 part (not counting discounts), and obviously are not considered preventative maintenance items.

i'm just more confused now. so the water pump and therostat are not considered preventative maintenance items?

so the only time i'd really replace it is like the chain, if i start hearing noises/it breaks?

[ENINTY]

Originally Posted by jimmyjames408

i'm just more confused now. so the water pump and therostat are not considered preventative maintenance items?

so the only time i'd really replace it is like the chain, if i start hearing noises/it breaks?

NO NO NO No! There are two basic engine designs when it comes to operating the camshaft. One design uses a rubber belt that has teeth on it that runs off of the crankshaft up to the cam shaft. The timing belt is located behind an unsealed cover and is somewhat exposed to the elements (i.e. water, salt, and dirt). Because it is a rubber belt it has a specific life expectancy, so it is replaced on a periodic basis to prevent it from breaking unexpectedly. If it breaks the engine will not run. Timing belts ARE a preventative maintenance item; and if they drive the waterpump then the waterpump is a preventative maintenance item.

The other type of engine design is a camshaft drive that uses a metal chain called a timing chain (instead of the rubber belt). The timing chain is driven off of the crank shaft up to the camshaft. The timing chain is encased in a sealed cover on front of the engine and is bathed in engine oil for lubrication and cooling. Timing chains are very robust and unless there is a manufacturing defect in the chain, or the engine is really abused, they RARELY break. Timing chains are NOT a preventative maintenance item.

Now what you are confused about is what type of engine design (timing belt or timing chain) also drives the water pump. On a traditional engine, if the engine has a timing belt, usually the timing belt is also used to drive the waterpump because it has to loop up around the camshaft (which is in the cylinderhead above the crank shaft) so it goes right by the waterpump pulley, so the engineers just drive the waterpump using the timing belt rather than the alternator belt. An engine that has a timing chain does not use the timing chain to drive the waterpump; the waterpump is driven using the alternator (i.e. serpentine) belt. In either design, the waterpump is mounted into a hole in the front of the engine block and is replaceable once the coolant is drained.

Now onto the E90 engine. The N52 and N54 engines in the E90 use a waterpump that is directly driven by an electric motor (i.e. there is no belt used to drive the waterpump). Because it is a separate, electrically driven assembly, it can be mounted anywhere near the engine. BMW mounts it on the lower right side near the front of the engine just above the steering rack; it is not mounted in a hole in the engine block like a traditional waterpump. Because the electrically driven waterpump is not susceptible to the normal wear that a belt-driven waterpump is, it does not normally wear out (like a belt-driven waterpump) and need replacement. However, like any mechanical device it can break for unknown reasons and need replacement.

If and when the thermostat fails is when you replace it. A failed thermostat on the E90 should not cause a breakdown, just an engine that is slow to warm up; so that is why it is not a preventative maintenance item.

I hope this clears the subject up for you.

[NaTuReB0Y]

Originally Posted by Chriztofor

Curious, did you ever change the coolant before the water-pump failed?

nope.....one rainy day my car just overheated

been great since.....

[Saintor]

If and when the thermostat fails is when you replace it

So you prefer to wait and potentially be left on the side when you could have avoided it?

Not me.

I am annoyed by the high cost but it is not much $ worse than cars that require a new timing belt + regular water pump + thermostat.

[Vasil]

Originally Posted by ENINTY

The water pump is electric and not driven by the engine belt system. The thermostat is separate from the engine block (it's actually mounted to the water pump). Being that the water pump is electrically driven, the failure of it is more related to production anomalities rather than wear. Waterpumps that are belt driven usually fail because the lateral pressure the belt exerts on the pump shaft eventually wear the seals and then bearings. Because the E90 water pump has no belt pressure as mentioned it will not fail for that reason. The only problem with this design is that you can't tell when the pump is starting to fail. Belt driven pumps have a weephole in them which provides indication that the inner shaft seal is starting to fail because it will allow a small amount of coolant to leak out for detection. If the E90 waterpump fails, it will show an engine overheating warning indictor in the gauges.

The thermostat fails open, so it won't overheat the engine if it does fail. Also, the thermostat operation is monitored by the OBDII system, and if not operating properly will trigger the "service engine soon" light.

You should replace either one when they fail. They are not a "preventative maintenance" item.

Excellent summary. Thank you.

[ENINTY]

Originally Posted by Vasil

Excellent summary. Thank you.

Hey, you gotta live it to love it.

Thanks. I'm just here to help

[Tom K.]

Originally Posted by Saintor

So you prefer to wait and potentially be left on the side when you could have avoided it?

Not me.

I drove my E46 for 2 months with a failed thermostat (no SES warning on my '99 model, just an old fashioned water temp gauge). As Eninty repeatedly stated, they only fail in the open position - meaning that water always freely flows through both radiator and engine block. Therefore the problem is the motor being slow to warm up, or not reaching operating temperature at all in colder weather. Since I got tired of not having enough heat in the car and the decline in gas mileage as the weather turned colder, I finally had it replaced.

So there is no way a BMW thermostat failure will leave you stranded on the side of the road!!

It is not a preventative maintenance item, but if you want to do so, it costs over $500 at a dealer as it requires a coolant flush. Personally, I'll save my $$ for the ever increasing cost of 93 octane.

Tom

[Saintor]

Actually I should have quoted this instead.

You should replace either one when they fail. They are not a "preventative maintenance" item.

I don't care about the thermostat, I was thinking water pump.

And if they are known to fail and the result is that you are left stranded, in my book, they automatically join the 'preventive maintenance' club.

Turnersport agrees (although they are obviously biased);
http://www.turnermotorsport.com/c-10...ter-pumps.aspx

Referring to the electrical water pump;

BMW Water Pumps are common failure items. We recommend replacing them every 80,000 miles.

[Tom K.]

Originally Posted by Saintor

I don't care about the thermostat, I was thinking water pump.

I understand.

As both the OEM water pump and radiator were in fine shape when I traded my E46 after 10 years and 97,000 miles, I think I'd hold off on both until needed.

But if you'll sleep better at night...

Tom

[ENINTY]

Originally Posted by Saintor

Actually I should have quoted this instead.



I don't care about the thermostat, I was thinking water pump.

And if they are known to fail and the result is that you are left stranded, in my book, they automatically join the 'preventive maintenance' club.

Turnersport agrees (although they are obviously biased);
http://www.turnermotorsport.com/c-10...ter-pumps.aspx

Referring to the electrical water pump;

Yeah, you'd like to replace any part that may fail as a preventative maintenance item, but waterpumps are just too unpredicatable and too expensive to call for a periodic maintenance item. My car is at 135,000 miles and the water pump is original. I just can't justify replacing a $500 water pump every 60,000 miles.

[fdriller9]

You guys should also look into the oil filter housing gasket. The gasket is common failure point and when it deteriorates, chunks can clog the thermostat and/or damage the propeller in the water pump.

Changing the ofh gasket on our cars requires you to drain coolant as well though.....

[Saintor]

Originally Posted by ENINTY

Yeah, you'd like to replace any part that may fail as a preventative maintenance item, but waterpumps are just too unpredicatable and too expensive to call for a periodic maintenance item. My car is at 135,000 miles and the water pump is original. I just can't justify replacing a $500 water pump every 60,000 miles.

The question is; do 75% of the original pumps make it to 120000 miles or 25%.

In the first case, I agree with you (you don't have to bother I guess at 135K).

In the second case, I prefer to pay upfront and avoid an emergency repair. 60K miles is probably a bit too early.

the statistic is hard to assess.

[Saintor]

Originally Posted by *********

You guys should also look into the oil filter housing gasket. The gasket is common failure point and when it deteriorates, chunks can clog the thermostat and/or damage the propeller in the water pump.

Changing the ofh gasket on our cars requires you to drain coolant as well though.....

Very interesting theory and I can't wait more info to support this.

Can somebody show an exploded view from realoem? I tried but could put my finger on.

[M3 Eater]

mine just went at 68K. CPO covered it! $50

[73tnh]

preventative maintenance on a water pump??? crazy. That's really OCD.