Duke

What's the difference between the 944-106-003-00 and the 944-106-921-X pumps? Roller mounting?

jeff968

I can't speak to the part numbers but Pete from RS barn did a great discussion on the 968s at the celebration and touched on water pumps. Apparently the original water pump had a plastic impeller. This impeller sometimes fails. The newer pumps that he uses have a metal impeller. Now the rated flow is not as high as the plastic but they have seen no difference in performance in many installations and feel better about the metal impeller.

RajDatta

I don't have PET handy but if you are referring to the difference between 951 water pump and 968 water pump, then one of the ports is blocked in a 968 water pump that is used on a 951. That is to connection to the coolant hardpipe on a 951.
Raj

Duke

No the 104mm blocks are different from the 100mm blocks so the pumps are different.
I'm comparing the 968 pump with the S2/2.7l pump.
Those blocks are equal so I cannot see why the don't share the same pump.

Luis de Prat

Possibly because the automatic tensioner in the 968 is hydraulic, whereas on the 944S2 it's a spring tensioner?

FRporscheman

Isn't that the connection with the plastic elbow fitting on the waterpump, that goes to the coolant reservoir?

I don't know what the difference is. I've taken apart a 2.7, a 944S2, and 968 engine and all the waterpumps looks the same, but i didn't look very closely I guess. I still have all of them, I can go compare them if you wish...

RajDatta

2.7 engines, s2 and 968's should all have the same waterpump. As a matter of fact, the pumo says 2.7l on it.
Arash, would you mind confirming this?
Raj

Thom

My new waterpump (for 104mm block) from Paragon came with no 2.5 or 2.7 stamping.

FRporscheman

Raj, you got it. The 2.7, S2 and 968 pumps I took off all had a "2.7" casting near the upper right.

I just ordered a new 968 pump last week for my other car and like Thom's it had no number at all. The impeller is the same size as the old "2.7" pump though.

nick_968

Raj, are you saying that a lot of cars (mine included) that are running 3.0 turbos with 968 waterpumps are infact not getting the correct flow round the system if they are not using a 951 waterpump with the 951 watercooling manifold for the turbo?

Julian Allen

The bypass Raj refers to is for the watercooled tubocharger--there's a small thermostat in the 951 water pump plastic housing (white rather than black), a crossover hard pipe and then an electric pump (to circulate for a short while after the motor is shut down), and other plumbing from the turbo to the coolant reservoir.

The overall body of the 2.5 & 2.7 water pumps is the same. The impeller is larger for the 2.7's and the receiving surface on the block is different to account for the different sizes of the impellers.

FWIW, I thought the -X meant the pump was rebuilt.

Duke

Exactly and the turbo water neck so to speak is always plugged on new pumps (has to be drilled out for a turbo).
But the question is why there is 2 different 2.7l pumps.
The plastic impeller might be it, or the different cam belt tensioner. Any other thoughts?

Julian Allen

My PET shows a supercession for both engines to the 944-106-021-24 number pump.
Supercessions may mean an improvement (seems unlikely for a model 15 years out of production) or just a new supplier (would seem more the case).

flipo

somewhere in 1994 the 968 waterpump got a bigger turbine wheel so it gets more water around ,I know becausse I put such a bigger pump on my 1990 951 and you have to grind down the engine block a few mm to make it fit.

nick_968

Ok so I need to drill out the extra next on my waterpump to get the turbo watercooling system to work properly.