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Be sure to inspect you pulley's and their bearings often!
I guess I'm an abusive owner...I've had factory pulleys fail at something like 12k miles. Now have the billet pulley bearings fail at somewhere between 15-20k miles.
I just want to make it clear...the pulley system works and has been great. What failed was the bearing which caused the belt to shred. This post is simply a PSA for all who drive hard to inspect your pulleys every oil change or every other oil change. To properly inspect a billet bearing, you'll simply need to remove your belt. For factory plastic pulley's the backside of the pulley's themselves may develop cracking around the bearing support. A good shake and tug should let you know if the pulley is still in good order for the most part. Even then without full removal, you may still miss something. Better yet, just replace those plastic things...they're bound to fail regardless. From what I do see...the bearing is a quality Nachi bearing from Japan. From my experience Nachi and NSK are high quality and before today I haven't had a failure. Now I'm trying to think if I should replace the bearing with a Timken, or replace with a Nachi once again. Oh well. I guess you gotta pay to play.
Cant speak for the quality on the billet ones, but if you killed stock ones in 12k you have other issues. Do you spray salt rust and acid on them or something lol.
I drive my car like it was a 3 cylinder geo metro and I'm trying to merge into the hwy. With the latest...I don't think 7,500rpm is favored by these bearings so ordered a higher spec bearing which should be arriving tomorrow. Let's hope this one lasts longer than a 1-2 years.
previous to the set of new OEM pulleys I killed at 12k the ones prior lasted 40-50k? I changed them out for safe measure not because of a failure. I do drive a lot more harsher than I used to. the ones that failed at 12k failed on a double gear kick down. that jolt of torque just broke the bearing support within the center of the pulley. It also took out my thermostat and housing.
here are the specs of the bearing.
NACHI 6203NSE bearing d - 17 mm
D - 40 mm
B - 12 mm
C - 12 mm
r min. - 0.6 mm
da min. - 22 mm
Da max. - 35 mm
ra max. - 0.6 mm
Weight - 0.065 Kg
Basic dynamic load rating (C) - 9,55 kN
Basic static load rating (C0) - 4,8 kN
(Grease) Lubrication Speed - 12000 r/min
(Oil) Lubrication Speed - 21000 r/min
this is what i'm replacing it with
NTN
6203LLBC3/EM
Type
Deep Groove Ball Bearing
Bore Type
Round
Material
High Carbon Chrome Steel
Cage Type
Pressed
Cage Material
Steel
Ball Material
Steel
Limiting Speed - Grease
18000 RPM
Seal Type
Non-Contact
Seal Material
Nitrile Rubber
Precision
ISO Class 0
Configuration
One
Factor
12.8
Radial Internal Clearance
C3
Static Load Rating
1030 lbf4600 N4.60 kN
Dynamic Load Rating
2160 lbf9600 N9.60 kN
Enclosure
Double Sealed
Weight
0.141 lb0.064 kg
Operating Temperature Range
-40 to 250 ºF-40 to 120 ºC
Dimensional Specifications
Single Row Radial Ball Bearing - Double Sealed (Non-Contact Rubber Seal) - Dimensions
d
0.6693 in17.000 mm
D
1.5748 in40.000 mm
B
0.4724 in12.000 mm
r
0.0236 in0.600 mm
r1
0.0197 in0.500 mm
da min
0.8268 in21.000 mm
da max
0.9055 in23.000 mm
Da max
1.4173 in36.000 mm
ras max
0.0236 in0.600 mm
Just order them all from FCP for 100 then just change them every oil change for free, no more issues!
going to end up doing this from now on. the new bearing has failed as well. the excessive wobble due to the single bearing design over time just gets worse and worse.
does anybody know if any brands offer a dual bearing design or a needle bearing design on an aluminum pulley? sad to say that the design is inferior and really has no place on a high reving engine.
Compared to ball bearings and ordinary roller bearings, needle bearings have a greater surface area in contact with the races, so they can support a greater load. They are also thinner, so they require less clearance between the axle and the surrounding structure.
11’ C63 AMG; D2 Audi A8; 15’ Golf TDi; 97’ F350PSD; B6 Audi S4; D1 Audi V8; A2 VW GTi
Needle bearing style wouldn’t last much longer. What limits small bearings load capacity are the speed of the rolling elements and their size. The larger in diameter the rolling elements (***** as opposed to needles) the longer it will last at a given speed, and the higher loads it will take.
If a bearing is meant to operate at very high speed with grease for lubricant it needs to have lots of internal clearance for component growth due to heating. So if you install a bearing with tight internal clearance and ask it to operate at max speed all the time it will not last long at all.
Also, a deep groove ball bearing will deal with some thrust, where a needle style will not deal with any.
You said it though, the main failure mode is the single row ball bearing. Bearings like to work in pairs. If you only have one row of *****, you turn thrust load into a moment load, and no bearing likes moment load.
A special pulley could be made I suppose, or the billet ones could be modified to take a double row setup but stacking height will be the limiting factor.
two more bearings on the aluminum pulley's stiffened up... then went to install OEM style pulleys and the threads pulled from too many removal and install cycles over the past 6 months.
I was chasing down an issue with my belt jumping for a long time so pulley's were being swapped and replaced quite a few times. that issue was due to my power steering pump missing it's rear bracket which was allowing the power steering to move back and forth on heavy load.
I'll be placing an order for a set of pulleys from FCP and new belt tonight. also looking into repair with Time Sert or Keenserts.
as far as abuse...I take my engine to 7,500rpm quite often. also at 155k now. took ownership of the car at 79k...the remaining miles have been fun to say the least.
Last edited by hachiroku; Dec 16, 2020 at 09:22 PM.
also, my own mistake of not replacing all bearings of the aluminum pulley's at the same time. when the other went bad the others were very solid and smooth...now 2 out of 3 are stiff.
looks like bs sls uses different idler pulleys for the top 2, uses the same 137 v12 pulley though. Also does your car have the lower pulley in between the ac compressor and crank shaft pulley?
Mb sells a fancy billet add on pulley kit for that bottom one you dont have. Just to clarify the pulley is the normal upper one, but the bracket adapter is billet. I added one on a clk63 bs one time. It was like $600 or something crazy though. cheaper than replacing the front cover i suppose if it comes to that.
Mb sells a fancy billet add on pulley kit for that bottom one you dont have. Just to clarify the pulley is the normal upper one, but the bracket adapter is billet. I added one on a clk63 bs one time. It was like $600 or something crazy though. cheaper than replacing the front cover i suppose if it comes to that.
no, this time the mid pulley and mid top pulley are overly stiff. the top left grooved pulley seems to still have decent rolling tension, but I plan to service this bearing as well. the tensioner pulley of which I swapped the bearing out 2-3 months ago still feels like new good rolling tension, not too much, not too little, and no oil seepage. I figure, with the abuse I put my engine through especially while tuning and high loads, I probably have a service life of 20k. as much s the lifetime warranty of factory pulleys from FCP entices me...i'd rather have the piece of mind of dealing with a bearing coming out of spec than a pulley snapping. i'll just have to pull off my belt every oil change to inspect bearing play and tension.
hopefully my choice in NTN was a solid choice. in my hand, although both C3 clearanced, the NTN has more play than the Nachi bearings they replaced which should aid in heat expansion, but only time well tell if that is enough.
NTN Bearing 6203LLBC3/EM Single Row Deep Groove Radial Ball Bearing, Electric Motor Quality, Non-Contact, C3 Clearance, Steel Cage, 17 mm Bore ID, 40 mm OD, 12 mm Width, Double Sealed
The frustration of finding a suitable replacement is the amount of variety of similarly sized bearings available. Some are dry bearings, generally with steel side casings. Some have completely open side casings. Others have different precision fit or groove spec. Then there is operating RPM and temperature. Honestly, most if not all bearings are simply packed with generic grease. None seem to register with high load, high speed grease that is commonly available in the aftermarket space.
Radial clearance is the play between the ball and raceway perpendicular to the bearing axis. Axial clearance is the play parallel to the bearing axis and is typically at least 10 times greater than the radial clearance. Generally, internal radial clearance will be reduced 80% of the interference fit amount.
Too little or too much internal clearance will significantly influence factors such as heat, vibration, noise, and fatigue life.
In extreme applications that see high or low temperatures this clearance needs to be considered in the overall design to compensate for thermal expansion and contraction of housings and shafts.
Internal clearance being C3 means that the bearing has room for expansion if needed between the races of the bearing, whilst holding the outer ring and moving the inner ring in a radial movement you will detect a little amount of play between the two rings. All standard clearance bearings have this movement, it may only be a small amount of movement but is controlled by international standards. C3 means the bearing has more clearance than standard.
For example we may use C3 clearance on bearings where a cold start up application my cause the ***** to heat up quickly, the heat needs to go somewhere. Some of the heat gets passed through the outer race to the housing and the inner race to the shaft, this causes expansion which closes up the clearance in the bearing. If you did not allow for this clearance the bearing would not have room for expansion and lead to bearing failure.
It is never advisable to replace a bearing with one having a lower initial clearance. By the same argument, it is usually safe to substitute a larger clearance when the desired clearance is not available.
Equal cross reference – Cross compatible replacement parts (list pulled from the internet but not actually validated for likeliness):
Yep. I.would say checking the pulleys is an important thing to do. This happened last year, but was an easy fix. Unfortunately I did not see any issues with the pulleys and decided to just put a belt back on on. They are now on my winter project list.
yeah, initially the reason I picked up aluminum pulley's was because the mid pulley or tensioner pulley failed kicking the belt up to destroy the thermostat bubbler/vent. well you can't replace that one piece so there went something like $220 or so for the part alone.
I also placed an order for a time sert kit. although keenserts are known to be better, they require a bit more meat removal than I am comfortable removing on my front cover. I'll probably end up inserting a time sert on all 3 pulley locations just to prevent threads from stripping again in the future. we'll see...
Last edited by hachiroku; Dec 17, 2020 at 04:43 PM.
thanks! can't seem to find a photo of it anywhere though. when I previously inspected my front cover in that lower area, there are no additional mounting holes.
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d - 17 mm
