Water pump change in design ?

lightguy

Member
Have to replace the Water pump on my 06 and the top idler pulley (part of the water pump housing) mount point is threaded for the attach/pivot bolt.
I've shopped a local parts store AND the Dodge dealer and the ones they have have a smooth drilled hole instead of threads. It would look like a different bolt and D shaped nut is the current design.Hole is too big to tap with the current bolt.
The parts dept image at Dodge shows a threaded bolt and no nut.
Any ideas as to what is going on ?
 

talkinghorse43

Active member
Did you check with Freightliner or MB Sprinter dealerships; or online in MB's EPC?
 

220629

Well-known member
...Any ideas as to what is going on ?
Yes. DO NOT THREAD TAP THAT HOLE.

The fastener has is a thread forming style. By design it makes its own threads as the fastener is installed. The formed threads have greater strength than regular tapped thread design. Just make certain that the bolt is aligned properly as you thread it into the new pump.

I think if you search for "thread forming" from the blue bar above you will find more information.

Have you found this thread? You might want to go to post #1.

https://sprinter-source.com/forums/showthread.php?p=142617#post142617
vic
 
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talkinghorse43

Active member
But, OP wrote "Hole is too big to tap with the current bolt."
 

220629

Well-known member
But, OP wrote "Hole is too big to tap with the current bolt."
Yep. :idunno:

But all the other information about an untapped hole fits what has been reported here other times. I'm thinking that after reading through the thread which I provided the guy will find that the parts fit as designed.

If not, I'm certain he'll get back to us.

vic
 

lightguy

Member
Yep. :idunno:

But all the other information about an untapped hole fits what has been reported here other times. I'm thinking that after reading through the thread which I provided the guy will find that the parts fit as designed.

If not, I'm certain he'll get back to us.

vic
Sorry;
Had some other work to do non-sprinter related.

Thanks for the link to the water pump change thread.

I'm going to bring my old pump and stuff to the dealer to see whats going on.
May need a new bolt, idler pulley, and or whatever. IIRC the old bolt fit in the new pumps bore loosely therefore cannot tap it. Larger bolt would mean a different pulley.

Kind of a goofy design if you ask me.
 

lightguy

Member
FYI
Turns out the pumps at Oreiley auto parts AND the Dodge dealer had larger hole bores for the self tapping bolt.
The one at the Feightliner dealer was correct.
 

220629

Well-known member
Interesting. An O'Reilly part may be a rebuild or otherwise different, so that's a buyer beware thing. The Dodge dealer should have OEM factory parts. Did you happen to find out whether the Dodge part was MB OEM or aftermarket? The Dodge water pump I purchased from our local dealer for my 2004 a while ago was an exact fit.

I'm not questioning you or your information, it just seems odd that the Dodge part would not be correct. :idunno: It's definitely something worth checking before walking out with the part.

I don't think that I kept my old leaking pump, or I would measure the original bore and put that information in my water pump Write-up. Would you please measure the backside bore diameter (that sould be less affected by the fastener) on your old pump and get back to me? Or maybe the new unthreaded bore if it isn't installed yet. Thanks.

Glad that you got it sorted out. vic

FYI
Turns out the pumps at Oreiley auto parts AND the Dodge dealer had larger hole bores for the self tapping bolt.
The one at the Feightliner dealer was correct.
 

lightguy

Member
I returned the "bad" pumps so dont know what the bore was.
The bolt threads all the way through the boss; there is no unthreaded portion on the old pump to measure. Old pump threaded bore measured with calipers (top of thread to top of thread) is .270.
Bolt OD is .312.
Bolt bottom of thread to bottom of thread = .275 = .005 interferance fit or else I measured wrong :thinking:
Hard to measure threaded bore with calipers.
Factory bolt was definitely sloppy in "bad" pump. Factory replacement bolt the same.
Dodge pump was factory Mercedes part for sure.
Beware of wrong bore in some pumps.
 
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