Water Pump, Underdrives and Serps!
 

I would like to do a poll. I have, ready & waiting to fit, the RSS underdrive pulley and new serp belt - but i just thought i'd check with you guys who has experienced any of the following scenarios:

Option1: Water Pump failed - No Mods or Maintenance
Option2: Water Pump failed - After changing serp belt only as maintenance item
Option3: Water Pump failed - After fitting U/D pulley and serp belt
Option4: No Failure - No Mods or Maintenance
Option5: No Failure - After changing serp belt only as maintenance item
Option6: No Failure - After fitting U/D pulley and serp belt

Hopefully everyone on this forum fits in one of the six. I am trying to explore if there is a link to failure and if for that very reason i should not bother with the planned modification.

Haven't worked out how to do a proper poll thingy yet!

With the under drive pulley the belt speed would be lower and all the belt driven accessories would be slower to protect them from the extra wear and tear of driving at highter revs a lot.

I don't think the belt tension would change and in theory the slower speed would make the accessories driven by the belt last longer.

I guess your trying to get some stats to see if this is actually the case?

What is the diameter of the original vs U/D pulley I'd be curious to calculate what percent slower it makes things over the original?

Hi jb,
Yeah, trying to get some stats along those lines and also trying to ex-sponge thoughts from my mind that the pumps may possibly fail once they have been disturbed.

I totally agree with your theory about them lasting longer as they are underdriven. However i want to work out if that would only really be the case if it was underdriven from day 1. Sometime, disturbing certain areas on these cars in the pursuit of power and vanity seems to upset their balance and result in the failure of a part which may have continued quite happily for a number of years if it had not be disturbed. Somethings are better left alone and i am wondering if this is one of those.

I have the part waiting, just unsure weather or not its wise to fit it to old smokey!

I had the water pump fail after installing the UD pulley and shorter belt - but with 120,000 miles on the original water pump its hard to find any correlation between the UDP and the water pump failure.

The UDP should prolong the water pump life by not turning it as many times as the stock pulley.

Read this thread: http://986forum.com/forums/general-discussions/37563-underdrive-pulley-questions.html

Thanks T-man,
You can see where I am going with this pole eh!

Essex....
You are correct re disturbing componants - within 2,000 km of me installing a new belt @ 65,000 km, one of the idler pulley bearings started making a rattling noise & a second bearing felt gritty. This my just be a coincidence, but one never knows....
I replaced all three idler pulleys anyway & also installed the underdrive pulley + new shorter belt.

I think that the only downside to the underdrive pulley is (maybe) that the battery charging can be low IF you drive short trips in traffic (low rpm) with the lights / accesories on.
When I installed my new pulley, I checked the voltage of the alternator and the volts were normalised @ 13.5v when the engine revs hit 1,800 rpm, so keeping above 2,000 rpm should be sufficient to charge normally - sometimes difficult in heavy traffic.

AT 30,000 my car was 7 years old and had not had a pump changed. The front motor mount was shot. Suggestions were do both at save some time. I installed Napa's best with a metal impeller, UD pulley and new belt. 23,000 mile and 2.5 years later it was still running. I rebuilt the new motor in the car with a Napa's Best again. Both the original in the 2.7 and the one that was in the 3.2 motor were good at the time they were removed. The Napa's best in the 2.7 is the same as when it was installed visually and by feel turning the pulley.

Bump..........
Push this back up the board - i'm hungry for data

I know England is small, but you must be really bored. :p

Gotta get to the bottom of these things PW. It's a Brit thing.

PW, at least tick a box man, come on!