Water Pump Replacement

[PeterW]

If you don't change the water pump at the same time as the timing belt, what's the risk? Do water pumps failures end up in catastrophy, or is it just that you could have saved the labour cost if you'd done it with the timing belt?

[Senninha]

I believe you've answered your own question in that to get to the pump you need to remove the TBelt so most recommend as a precautionary and cost effective time to do the work. I dont know how/if you can test the pump to know if it needs changing.
If it fails then an over heating engine is not a good thing and results could be more costly then not changing when you have the opportunity.

HTH, Paul

[Kaz-kzukNA1]

Hi, PeterW.

Depends on the spec of your Water Pump (WP) and the Failure mode.

If your WP was the old design, then quite often, it no longer line up/seat well against the seeping hole at the Timing Belt (TB) Lower Cover (old design).

Under this condition, quite a lot of coolant can leak inside the TB cover when WP got very-very old.

With this design, it is difficult to spot the first sign of the failure so it could end up in catastrophe as described below.


By the time when you noticed the coolant leakage (tiny-tiny amount over many years is normal) under the TB cover, some coolant may have already in contact with the TB.

Because of this, Honda modified the design of both the WP and TB cover long time ago so for quite a while, even if you ordered just the WP, it was delivered as a set of new design WP and TB Lower cover.

Nowadays, you can order the WP and TB lower cover separately (if you want) but I don’t see much point in doing so if it is for the TB service.


Unlike the TB on old Prelude, the one on NSX is quite robust/strong but if your TB was not tensioned properly, it could easily jump a few teeth if it was wet by the coolant and applied sudden reverse torque such as stalling the engine.

Not good...

Your engine will run reasonably well at high rpm if it was just a single tooth jump so you may not notice the timing issue.


If you kept the TB contaminated for longer period, the ribs on the TB could be stripped off but I don’t have any test data for this on NSX TB.

It was tested on other models.


If your WP has seized (I know at least two NSX in Japan and one NSX at my local Honda garage), that’s a different story…

Only one’s fate will decide the outcome.


Water Pump (WP) is driven by the back surface of the Timing Belt (TB).

Therefore, if WP has seized, it will apply significant drag to the TB.

Who knows what will happen under this condition.
All three NSX above managed to escape the serious engine failure but two JDM ones over heated the engine but without any head damage.

Overheat condition won't immediately damage the engine and it depends on at what point you have noticed the hot condition.

Personally, I recommend replacing the WP at the time of TB service regardless of the mileage covered.

If you don’t replace it, you are going to rely on it until the next TB service which is another 5 or 8 years (TB service schedule for UK models) time...

I hope I didn't scare you too much ....

Kaz

[PeterW]

Hi Kaz,
v informative answer thanks.