Diesel water pump failing?

[Sebastienclement]

Chaps,

i'm not terribly mechanically competent, so would appreciate some views on this.

Going into winter I noticed my 75 struggling to keep the cabin at a decent temperature when stood stationary in traffic. I have been running it with the onboard diagnostics on and have observed the following:

1. Normal driving sees the car achieve 87'c and stay there - whether I'm pushing it hard or feathering it. Cabin remains toasty.

2. After about 10-15 minutes of sitting in traffic, engine temperature creeps up to 90'c - this coincides with the heater cooling down. It never goes cold, but decidedly luke warm.

3. Holding the revs at 1500 rpm while stationary brings the heat back to the heater, and brings the engine temperature back down to 87'c.

4. One driving again all is honky dorey.

To my (very) simple mind this could be symptomatic of a failing water pump, which is not circulating water well enough at idle? Or perhaps a characteristic of the engine? other 75 owners have found the cabin struggling to maintain heat when idling - but I can't find any references to engine temps increasing too.

[TomRS]

This will be down to the efficiency of the engine.. what you are seeing here by being sat in traffic with the heater on you are taking away heat from the engine thus closing the thermostat hence the hike in water temperature, this means that the rest of the cooling circuit is cooler meaning you lose some cabin heat.

The drop back down to 87 degrees is the stat re-opening and controlling the flow.
Basically with the colder temps being sat in traffic for extended periods with the heater on high will cool the engine down much like being sat with the radiator fan running.

[Jakg]

Sounds pretty normal to me - don't think i've ever heard of a water pump failing ont he diesel.

[Mike Noc]

You have now, I've replaced two on mine.

First one failed just shy of 300k miles - bearing collapsed throwing the belt, and the aftermarket replacement from ECP, a Circoli, around 60k later.

[COLVERT]

For some reason or other that 90 degree reading is not accurate.

The heater running with the car stationary will remove more heat than the engine is producing. The dash gauge will drop from the 9 o'clock position.
Mine does exactly that.

As the engine temperature drops the thermostat will close. You are then removing heat from just the engine itself and not the rad. The longer you sit there the lower the temperature will go giving you a cold draught in the car.
The dash gauge drops, though how you are getting a 90 degree reading I just can't say.---

[TomRS]

Originally Posted by COLVERT

For some reason or other that 90 degree reading is not accurate.

The heater running with the car stationary will remove more heat than the engine is producing. The dash gauge will drop from the 9 o'clock position.
Mine does exactly that.

As the engine temperature drops the thermostat will close. You are then removing heat from just the engine itself and not the rad. The longer you sit there the lower the temperature will go giving you a cold draught in the car.
The dash gauge drops, though how you are getting a 90 degree reading I just can't say.---

Mine used to do exactly what he has written and it had new water pump/new aux belt/thermostat.

Unless there is underlying issues.

[T-Cut]

A partially silted up heater matrix would explain all the results noted here. The display temperature I'd say is correct because there's no reason to doubt it and they are rarely that inaccurate. I'd suggest it's simply the lack of adequate flow through the heater matrix at low revs (low pump pressure). Even with 90C coolant temperature, if it's not flowing fast enough there'll be poor heating in the cab.

TC

[COLVERT]

Originally Posted by T-Cut

A partially silted up heater matrix would explain all the results noted here. The display temperature I'd say is correct because there's no reason to doubt it and they are rarely that inaccurate. I'd suggest it's simply the lack of adequate flow through the heater matrix at low revs (low pump pressure). Even with 90C coolant temperature, if it's not flowing fast enough there'll be poor heating in the cab.

TC

My heater works really well. The matrix is so efficient that with the engine running ,while my better half does the shopping, the gauge drops from the 9 o'clock position quite quickly.

The likelihood of the impeller fins in the water pump of the diesel being eaten away by cavitation is quite remote considering how slowly it spins.
( Especially with OAT anti-freeze. )---

Most of my driving, up to 60 mph, is below 2,000 rpm. I would suggest the same for most DIESEL-- Drivers. A thing that you petrol heads wouldn't know too much about.---

These DIESEL engines are so efficient they use all the energy released from DIESEL to push the car along and not lose it into the atmosphere.

50 mpg plus is the UP side.--

The downside being a slightly inefficient heater when being used with the engine ticking over.---Guess you can't have it all.

You petrol heads throw away 25 mpg, just to make your heater work.--

[SD1too]

Mr. Colvert Sir, I do detect in your last post that your usual high standards of impartiality are being compromised by a sense of loyalty to Mr. Rudolf Diesel. I feel the need to restore a sense of balance.

Originally Posted by COLVERT

Most of my driving, up to 60 mph, is below 2,000 rpm. I would suggest the same for most DIESEL-- Drivers. A thing that you petrol heads wouldn't know too much about.---

Well John, my 2.5 litre V6 with automatic gearbox travels at 55 mph when turning over at 2,000 rpm. What's 5 mph between friends?

The downside being a slightly inefficient heater ...

Slightly inefficient? Although I haven't had the Rover 75 diesel experience, I have travelled in many freezing cold diesel London black cabs and "slightly" is not the adjective I would use!

You petrol heads throw away 25 mpg, just to make your heater work.

No, not just to make our heater work (and what's wrong with being comfortably warm?). Other advantages of petrol engines are lack of NVH (noise, vibration and harshness) and consistent power delivery over a much wider rev band. They also don't chuck filthy soot into the atmosphere and comply with far more stringent emissons regulations.

I'm sorry John, but when it comes to Dr. Diesel's "infernal machine", the petrol heads have it.

Simon

[grivas]

Originally Posted by COLVERT

My heater works really well. The matrix is so efficient that with the engine running ,while my better half does the shopping, the gauge drops from the 9 o'clock position quite quickly.

The likelihood of the impeller fins in the water pump of the diesel being eaten away by cavitation is quite remote considering how slowly it spins.
( Especially with OAT anti-freeze. )---

Most of my driving, up to 60 mph, is below 2,000 rpm. I would suggest the same for most DIESEL-- Drivers. A thing that you petrol heads wouldn't know too much about.---

These DIESEL engines are so efficient they use all the energy released from DIESEL to push the car along and not lose it into the atmosphere.

50 mpg plus is the UP side.--

The downside being a slightly inefficient heater when being used with the engine ticking over.---Guess you can't have it all.

You petrol heads throw away 25 mpg, just to make your heater work.--

And therefore the remarkable Webasto heater, the most important add-on for the BMW diesel, as has been said above these engines are so thermally efficient that they struggle to keep the cabin warm, as the guys whose cars are not equipped with one soon find out when is cold out there.