Water Pump Failure - Diagnostic Steps?

This weekend I started troubleshooting an engine clattering noise at idle (500RPM) on cold start-up. Clattering dissipate at higher RPMs (800 and up) and after engine warms with gauge reading (160F). Idle oil pressure cold is 60 to 62 and 30 to 40 when warm/hot after good run.
Briefly ran engine from cold with fan belt removed to isolate any rotational noises and noise was eliminated. Generator was replaced with a good spare one, attached fan belt, ran engine from cold and clattering noise returned.
So, if the clattering noise is not from the Generator / alternator, could it be the water pump? How could this be tested? There’s no apparent telltale leaking or loose pulley. I have good spare water pump (lightly used from early 2000) available to test this idea. I’d like to avoid “plug and play” approach, but if there's no other diagnostic suggestion, then I'll give it a try.

Any shared thoughts are appreciated, GONZO

usually if a water pump is going bad to the point of making a noise, you can wiggle the fan.

Just replace water pump with new or have it rebuilt

If you have a decent older pump you can rebuild it with a kit from Mike Salter, or have him do it. I've done it both ways and it is easy for anyone who's handy to do it themselves.
You have to clean up the sealing surface on the impeller. I did it with a file on a drill press.
Michael.Salter:atgmail.com

pull the drive belt and run the engine. If the noise goes away it is belt driven (generator or water pump).

Another idea short of replacing the water pump would be to get a belt short enough to run the generator only.

Since you've had the problem with two generators, the problem must be in the water pump.

Free spinning the water pump and generator /alternator does not reproduce the noise; it's only under "load" with belt attached and correctly tensioned. There are none of the typical water pump symptoms;overheating, weeping or loose pulley etc. but it is about 20 years old so maybe age plays into this.

I was also thinking of a shorty fan belt to put the generator / alternator under load for a more definitive test. A replacement WP (NOS) and new gasket are at the ready. Prepping the car for the San Juan Capistrano Car Show Sat Feb 3rd. Thanks all. GONZO.

I'd be listening for a loose timing chain due to a bad tensioner . The chain can rattle against the cover a bit. Just a thought.

You could try listening in, using a long extension from your socket set - grip the top in your fist and put the bottom end on the 'offending' area and put your ear to the top end, alternatively use a stethoscope if you have one. Just be careful of that fan/pulley etc.



Bob

When you're at the car show, you could use Bob's suggested stethoscope method to compare the sound of your cam chain/water pump with someone else's.

I once had a dry rocker end that started making a terrible clatter - sounded like someone was beating on the engine with a hammer. You could try adding some Marvel Mystery Oil and see if it goes away.

I bought one of these years ago:

https://www.harborfreight.com/mechanics-stethoscope-63296.html

Believe it or not, it doesn't suck!

Good suggestions. Some initial checking with HF stethoscope shows only some light whirling noises emanating from dyno/alt and timing chain cover area - I was worried of getting too close to rotating fan and belt etc. I'll be checking again. I'm hoping it's not the cam sprocket and timing chain. But if I decide to replace the water pump, then 50% of the disassembly to access the timing gears and chain is done. Thanks, Gonzo

Gonzo -
Weather's pretty cold by SoCal standards right now so you could drive your car without a fan belt for a ways...
Returning to the idea of removing the fan belt completely - you could even remove the thermostat to make it take longer to heat up. Do this a couple of times from cold and you'd have a comfort level that it wasn't the timing chain...or you'd know it was.

If you want to be really sure it's the water pump, then install a short belt to the generator and do the same thing a couple more times. If no noise at that point, reinstall the regular belt and see if the clatter returns.

I'm having a hard time visualizing (audiolizing?) a water pump making a clattering sound if the shaft isn't wobbly. Grinding/grating sound yeah, but clattering, no. I guess if the ceramic seal is broken you'd get a clattering sound, but you'd also be leaking.

On another forum there was a discussion about aftermarket chain tensioners coming apart*, which would make a clattering noise, at least until the pieces settled in the timing cover, but it doesn't sound you're hearing that.

* DWR makes a re-engineered part to address this. Wish I'd known about it when I recently built my engine.

As a thought and please don't shoot me for this - has your crankshaft damper been renewed in the recent past for one of those bright shiny types or is it the old original type? - The old ones can come apart with age.



Bob

At cold start up and engine idling: fan belt off no clattering, belt on clattering. Clattering goes away with RPMs >800 - 1000 and engine temps warm up but can be reproduce when engine RPM drop or under load - like when slowly rolling in 1st or 2nd gear engine lugging. I have a couple more test conditions to try with stethoscope probing before tear-down.

BTW, an aftermarket chain tensioner was installed about three years ago, despite its cheap construction. The BJ7 has a two piece harmonic balancer with damper ring bolted up in 6 places to the drive pulley. This was inspected and in good shape. Redisleeved pulley shaft to properly seal and finally new timing chain cover gasket and seal to finish the job. A DWR chain tensioner was purchased afterward and its impressive. I also may have the original tensioner resurfaced / renovated.

Grabbed my NOS water pump off shelf and inspected. Good condition but has bolt-on 3/8 in. pulley only compatible with puny original and not any aftermarket fans. I may be going OG with this fan, but it'll be re-painted bright yellow for show. Gonzo.

Pulled radiator for a closer look at the Harmonic Balancer etc. and quickly found a loosened crankshaft nut with its locking tab just barely holding. HB was a little loose too which allowed for a small degree of rotational movement observed earlier (3 to 5 degrees). Re-tighted nut and re-folded locking tab, mading sure to lock two flats on the nut instead of just one tab as before. The "clacking" noise at idle attributed to all this looseness or play is now eliminated. So, it was not the water pump, generator/alternator, or timing chain etc. For those who suggested a Harmonic Balancer issue get rewarded with a cookie!

Now I can drive with confidence again. Thanks all, Gonzo