Disco Heat

[Adrift]

Hey folks,

Quick question, The past couple of days when driving to class or just out and about the disco has started to run hot. When I notice the temp guage starting to climb I press in the clutch and start to pull over, and suddenly temps shoot back down quickly (within 30 seconds). I can then carry on driving as normal, of course always eyeing the guage for any movement. This has happened 3 times now, temp guage never gets high enough to get into the red zone.

Before throwing money at a possible solution I thought it out as to what it may be. I then remembered that the disco has been oddly silent on cold start-ups for the past week. So I go outside and start her up after she had sat over night, outside temp in the ~40s. No jet engine roar from the main fan at all. I then remembered that the electric fan has been kicking on alot lately as well. So I drove around for awhile till engine temps were @ normal operating range; stopped the engine and checked for free-spinning in the fan. Sure enough I can spin it all the way around without it stopping.

Here's the kicker though; later that day I started her up to run to the store and I got jet engine roar for about 5 seconds.

So what say EXPO? Fan clutch on the far side of failing? Check other components? Burn it?

 

[Adrift]

Cough... Kinda important. Anyone?

 

[dieselandmud]

First, how many miles are on the engine?

Second, does the fan turn freely by hand when the engine is hot? (engine turned off when testing this)

Third, look at the back of the alternator. See the big wire that runs to the battery? Is there any corrosion on the copper strands just before the protective plastic shield? Nut tight?

Fourth, inspect the fins on the radiator. Are they all intact? Also are all the fan blades intact? Coolant level ok?

 

[Adrift]

84K miles

Fan turns freely by hand when hot. I hear its only supposed to be able to spin 1/4 turn or so by hand when hot normally.

Will have a look at the alternator in a bit.

All fins on rad look good and intact. Fan is in great shape. Coolant level is full and stable (not losing any noticeable amount over time)

EDIT- Checked the Alt. cable on back looks fine, bolt is tight.

 

[dieselandmud]

I would say you need a new fan clutch. If there is no resistance on the current one.
I have part numbers for a Heavy Duty clutch if you want to go that route. It will be louder and you will take a small hit on horse power and mpg. I bet it will never over heat again.

 

[Adrift]

I was looking at a Hayden fan clutch from Summit. It says heavy duty, i dont know though.

part number = HDA-2991

 

[4xdog]

If this were an XJ Cherokee, I'd say air in the cooling system. Temperatures shooting up and down really fast sound more like a measurement issue. My British experience is all prehistoric, like my '62 TR3B, so I'm not your best source of info.

The title of this thread, though, does take an early lead for the most entertaining title of 2011 award! Just think of all the directions this one could go.

 

[Antichrist]

Definitely sounds like you need a new viscous clutch.
Std Duty Imperial 215257
Hvy duty Imperial 215158
The Hayden will work too, but I've never used one personally.
You'll need to drill the fan blade mounting holes larger, otherwise they fit.
Std Duty should be fine. Either one can be found at Advance Auto, Autozone, etc. I have one of each of the Imperial and they both do the job, though the HD one runs a lot more.

But also clean out the radiator fins. They are probably clogged with debris. Best way is to pull the radiator and use a pressure nozzle on your garden hose from the back side.

 

[Snagger]

You can temporarily botch the fan by using cable ties to lock the fan rotor to the viscous hub, but you should replace the hub ASAP. Remember it has a left-hand thread when you do it!

The auxiliary electric fans are for the aircon system when the vehicle is at low speed and the main fan is not providing enough cooling for the engine and aircon condenser together. They are not for primary engine cooling.

Have a good look at the condition of the radiator, looking not only for blockages of mud or insects, but also for corroded fins which have broken or twisted and blocked the airflow. This is a big problem after about five years on the UK's salted roads, so could be a problem for you if your roads get salted in winter or if the vehicle is often used near the coast.

Also check the condition and tension of the fan belt or serpentine belt, as it may not be turning the fan and water pump fast enough if slipping (though you would normally see low alternator performance if the same belt drives that - it depends on the engine fitted).

Finally, if everything else is in good order, use a couple of flushes with a good brand of cooling system cleaner to de-scale and clear out the whole system.

 

[jpc1818]

try the cheapest option 1st.

i would try flushing the cooling system.
I had the same problem in my 98 disco.
i hooked up the garden hose to the hose that leads into the heater core.
I flushed both ways (towards the core and towards the radiator), then replace antifreeze.

Let us know,