Viscus fan and water pump?

Hello,

My p38 overheats at infrequent intervals: i lose power and need to wait for the engine to cool down.
How do i tell if the water pump is not working?
How do i tell if the viscus fan is playing up?

If i replace the water pump will i also need to replace the viscus fan? (do they work in conjunction with each other or completely separate ?)

Iv'e tested the thermostat twice, boiled water from the kettle placed it in a jug with the thermostat and on both occasions the thermostat opened.

I also have cold air coming out of one side of the cabin when the heating is turned on could this be part of the same problem?


Thanks for any help and guidance that my help resolve this situation.


MIke.

In reverse order;
the cold air in one side of the cabin means that you've got hot air in the other so the heater is heating so the heater core is heating up so that's almost certainly a fault in the electrics of the heater.

The viscous fan and pump are totally separate.

Without an old fashioned rad cap to look down into and see the water being pushed along it's difficult to prove/disprove a pump. You're as well to whip it out. At your age you've probably got one with the plastic impellor. They can break up so you're as well changing it. If you find that it's already broken up make sure that you get every bit of the old one out. Replace it with a metal one.

Testing the fan sounds a bit black magic. When you first start from cold it will spin quite vigorously then, once the viscous fluid gets moving inside, the fan turns but with no power behind it until the engine, and therefore the fluid, heats up then the fan is driven round. So, start your engine from cold, wait a minute then stick a rolled up newspaper into the fan. You should be able to stop the fan. It's not over technical but it's about the best that you can do. If you have working air-con try turning that on if you overheat again. The fans on that are as powerful as the viscous and can even be used instead.

im having this problem also on my disco, how hard is to change the pump and viscous fan unit???? (found lots of units but no complete fan units??)

i suspect mine is shot as isnt very stiff at hot temp (temp gauge well up)

sorry for hijacking, just thought i might be able to piggy back on the problem

dogsbody said:

In reverse order;
the cold air in one side of the cabin means that you've got hot air in the other so the heater is heating so the heater core is heating up so that's almost certainly a fault in the electrics of the heater.

The viscous fan and pump are totally separate.

Without an old fashioned rad cap to look down into and see the water being pushed along it's difficult to prove/disprove a pump. You're as well to whip it out. At your age you've probably got one with the plastic impellor. They can break up so you're as well changing it. If you find that it's already broken up make sure that you get every bit of the old one out. Replace it with a metal one.

Testing the fan sounds a bit black magic. When you first start from cold it will spin quite vigorously then, once the viscous fluid gets moving inside, the fan turns but with no power behind it until the engine, and therefore the fluid, heats up then the fan is driven round. So, start your engine from cold, wait a minute then stick a rolled up newspaper into the fan. You should be able to stop the fan. It's not over technical but it's about the best that you can do. If you have working air-con try turning that on if you overheat again. The fans on that are as powerful as the viscous and can even be used instead.

Click to expand...

Sorry that will prove nothing, it's the opposite of what is needed. With the engine hot, stick your rolled up newspaper into the blades taking care not to insert the had, if the fan stops it's fecked
I can give you a mod to use the aircon condensor fans instead of the viscous fan if it's a diesel or as a supplement if it's a V8. On the V8 the fans should come on in an overheat situation in any case
Again if it's a diesel, repeated overheats will crack the cylinder head.

im having this problem also on my disco, how hard is to change the pump and viscous fan unit???? (found lots of units but no complete fan units??)

i suspect mine is shot as isnt very stiff at hot temp (temp gauge well up)

sorry for hijacking, just thought i might be able to piggy back on the problem

Not a hard job on a v8 Dodge.
But its well worth getting a viscous fan spanner before doing the job,so much easier than a hammer and punch/chisel
Also water pump bolts have a habit of shearing off when you least need them to,so a tap and die set and quality drill bits would be a good back up plan.

make sure you check the rad, it must be hot all over,if you have any cold patches then i would dump the rad,flushing is useless.i change rads aound here(wiltshire)on a 10 to one ratio against broken finned waterpumps

No problem,

when i sort my problem i will give feed back. Elimination is a pain.

Cheers...

Thank you all for helping.

Right, I have had the air con fans wired up so they can be operated manually from a switch inside the cabin. There is also an inline electrical sensor fitted to the top water hose on the right hand side of the rad as you look at the front of the engine. If the water heats up to 87 degrees as it passes the sensor the air con fans kick in.

I can't remember if the air con were working automatically at the time of overheating, i think i used the manual switch. (good call having that fitted.)

I've tested the thermostat three times (you know putting it in boiling water) it worked each time.

I took off the small hose (the one that feeds the header tank) at the radiator and the water flow was only about two to three inches. I think it should have more pressure than that.

Now the thermostat is out is there a way of testing the water pump?

Once again....

Thanks guys.