engine coolant impeller

[REBrueckner]

Can anyone provide some insight into checking the coolant pump on my 8V71TI. Any special tools required ? I assume this is a centrifugal pump...how can you tell when the impeller needs replacing?

My stbd engine runs a bit warm and if recentlycompleted work on my intercoolers didn't fix it, my mechanic suggested I look at the coolant pump rather than the thermostats (now about 7 years old). The HE will be phosphoric acid cleaned my next visit per Genesis instructions.....I 've made the hose connection kits and am ready to go....I've checked just about everything else.

[Nonchalant1]

Yes, it's centrifugal. It's a bronze impeller on a stainless shaft, but it's tough to work on.

First, you gott'a know if you have the newer high volume pump or the old pump. If yours has 5 bolts on the faceplate, it's the old one. If it has a big retaining ring faceplate, it's the new one. Hmmmm........ sounds like DD was fixing a problem.

And BTW - you can't just put the new bigger pump on. It needs a bigger oil cooler inlet and a smaller camshaft vibration damper.

You have to take the whole heat exchanger off to get the pump off. Taking off the retaining ring can be hazardous if that big strong SOB gets away from you. You need a special puller to get the old ceramic seal out and you have to bake the impeller at 500 degrees to get the ceramic face out, and then need special aligning inserts and a clamp to bake the new seal adhesive at 375 to put a new one back in.

Since these are pretty much bullet proof, I'd look elsewhere first.

Doug Shuman

[Traveler 45C]

And BTW - you can't just put the new bigger pump on. It needs a bigger oil cooler inlet and a smaller camshaft vibration damper.
Doug,

Do you have a reference for that? I didn't see all that in the DD manual. It does however, state that the newer pump requires a different drive gear then the old.

I've got to replace the pump on my 871. It's leaking coolant from the weep hole.

[Nonchalant1]

Trav,

It's in my 8V71 service manual, which also includes many other pump differences, removal, overhaul and reinstallation. I just wanted to 'splain that it seems like a really big job unless you know you have to do it.

My manual is on CD and it comes up in Adobe Acrobat. I don't think I can copy/paste it, but I could try, or at least quote whatever parts you are interested in.

Doug

[Captned]

I just replaced my starboard one. $280 with core charge from DD. It was 29 years old. FWIW, when I replaced my port one last year, my creeping temperature problem in that engine went away...

Captned
8V71TI
78 46 CONV

[Nonchalant1]

Ed,

That's really good info. Could you tell if or what was wrong with it? Not sure what can go wrong with one if the metal's still all there and original shape. I guess it's not bullet proof after all.

Doug

[REBrueckner]

I'd also like to know what can go wrong.

I just replaced the coolant circulation pump on my Webasto diesel heater. It's a minature centrifugal. (The boiler was getting hot, but ten feet away the hose was luke warm via hand so I figure there must be a water circulation problem.) Before installing the new one, I compared output pressure by running each in a pail of water and putting a finger over the outlet.. Sure enough the old one had a lot lower pressure than the new...and it had trouble picking up water to develop suction.....so it appeared "worn"...these are magnetic driven, sealed in an outer covering, so I did not bother cutting the old one apart to see what was inside... besides, I was too busy cursing having to work in a very awkward (naturally, it's a boat!!) position...

[Captned]

All I know for sure is that when it was on the counter at the DD shop, I would spin the pump, it would squeal slightly, and all the cuban mechanics looked at it and went" Ahhh, si, si!" and nodded thier heads..
I guess it was time to replace it! :)

Captned
78 46 CONV

[REBrueckner]

A squeal likely means the bearings are going...just like the water pump sounds on a car when it's tired....but that shouldn't affect the actual coolant circulation....

[yachtsmanbill]

Generally speaking, centrifugal pumps contain pressure by two wear rings around the impeller. The case ring on the frame ( along with the mechanical seal ) and the suction eye wear ring on the front. On a 3 inch diameter impeller, you probably run about .006" clearance. In laymans terms, thats about 3 blond hairs. Anything more and you start to lose pressure. A new pump may squeel, and thats a DRY seal. Thats a HIGHLY polished carbon ring against a HIGHLY polished hardened (chromed) ring with spring pressure. Thats why its paramount to run glycol or at least a water pump lubricant. Water isnt slick enough.
Bad bearings will growl when you turn it. A new pump should feel real smooth with a little resistance. Once the seal starts to leak, it goes right into the bearings. Thats why the tell tale weep hole is there; to see the leak and reduce coolant / bearing contact. ws

[SKYCHENEY]

I'd also like to know what can go wrong.

I just replaced the coolant circulation pump on my Webasto diesel heater. It's a minature centrifugal. (The boiler was getting hot, but ten feet away the hose was luke warm via hand so I figure there must be a water circulation problem.) Before installing the new one, I compared output pressure by running each in a pail of water and putting a finger over the outlet.. Sure enough the old one had a lot lower pressure than the new...and it had trouble picking up water to develop suction.....so it appeared "worn"...these are magnetic driven, sealed in an outer covering, so I did not bother cutting the old one apart to see what was inside... besides, I was too busy cursing having to work in a very awkward (naturally, it's a boat!!) position...

The biggest problem I've had with Webastos is getting the air out of the system. Once you get it bled they seem to pump fine, but that little pump is just not strong enough to force the air through the whole system. A well designed system will have all of the runs slope up to the expansion tank so that the air collects there, but it's hard to do that especially on a boat.

What do you have hooked up the it? I put one in a bus conversion and we used it for interior zoned heat, domestic hot water, and engine block heating. Those are pretty neat little boilers.

[Nonchalant1]

Thats why the tell tale weep hole is there; to see the leak and reduce coolant / bearing contact. ws

The genius of the weep hole is also that if either seal wears out, it can't cross contaminate oil into coolant or vice-versa. It just dribbles out.

Doug

[Traveler 45C]

And dribble mine does...

I'll have another look at my DD manual.

[REBrueckner]

Webastos: "...The biggest problem I've had with Webastos is getting the air out of the system..."
I have not had that problem; mine seems to purge air well, but it's a common problem...A local mechanic who works with them suggests a "tee" at a low spot for connection to pressure water supply...let the external water pressure push through the hoses/radiators/appliances etc. I guess you could also pump an antifreeze/water mix this way via an impeller pump from a bucket...

If the boiler is relatively low or at the level of other appliances and the expansion tank higher thanother components, the air should move through more easily...

My webasto is for heating the boat interior only..via car like fan heaters..I did not want to go the added mile to heat engines/genny/domestic water because I would have used a heat exchanger for each....and more pumps... but's it's a real nice set up, especially in cold weather... When I run my genny for battery charging, I also run electric block heaters and the electric water tank coil to give the genny some load...

[doc g]

As far as I have seen ,the coolant pumps on DD's almost never fail . When there is a problem it's leaking from the weep hole but I've never seen a temperature change when I changed one. They still pump fine even when they're leaking....................................Pat

[Traveler 45C]

From what I gather after taking a look at my DD Manual there are 3 pumps discussed: a former (old), a current (DD changed the driven gear) and a high capacity pump (this one has the larger in/outlets).

If I’m reading this correctly, the former pump is discontinued. The current pump has a different driven gear than the former, so replacement of the drive gear on the cam is necessary to use this pump.

When I rip the old pump off my eng and take it to the DD guys, what am I gonna’ get as a replacement, a former or a current pump? Is the current pump the high capacity pump discussed?

What’s involved with RR the drive gear? Is that something I can do while sitting in front of the eng?

The pump comes off tomorrow… please straighten me out on this…:confused: