I was driving today and suddenly I smelled coolant so I looked at my temperature gauge and it was at ¼ (cool end), I stopped and opened the hood. The coolant reservoir was bubbling and letting-out the coolant. All the hoses were fine and no apparent problem so
I borrowed a container and refilled the reservoir (and I bleed the system by opening the little plug at the radiator). The water pump seems in working condition since I could see a recycle through the radiator opening. My mechanical fan has being out for a while and the electrical fan works fine… starts by itself off and on.

I drove on a bumper to bumper traffic for about 15 minutes and everything was fine. As I was entering the expressway, then the problem started again (cold at the temp gauge but obviously overheating).

I got home and purged the radiator again… test drove and same thing happened after about 10 minutes.

I suspected a thermostat stuck closed so I took it out and it seems in good working condition. Is dark now so I will try and see what happens with out the thermostat tomorrow.

Any ideas why I will have cool temperature at the gauge but bubbling and escaping coolant at the reservoir? Is my diagnosis of bad thermostat right?

Thanks

 

Ed,
You may have a failing temp sensor so your guage is not getting correct info. Why are you running around with out a working main fan, are you try to see howw long it will take before your engine is TOAST???
Yes, your t/stat could be acting up, for $12 I would change it and put on a new fan hub today if you don't want any long term head or block problems.
Mike

 

Hi Mike,
Is there a way to test the temp sensor... with a voltmeter that is? It puzzles me because the gauge does move as normal (down when cold and goes up as it warms up… just not HOT)

NO… of course not. Here is the story:

About a year ago, I posted a question about running with out the mechanical fan (I can’t remember if it was here or a UK forum I was following). I explained that my fan clutch was bad and the previous owner welded it to the fan and it was extremely loud; not to mention that I have heard numerous stories of disasters after fan blades brake (especially in this case that my fan was spinning all the time according to my engine’s RPMs.) I received a few answers telling me that some people in the UK (that don’t do off terrain with their Rovers) take the fan off and are running with out problems. With this, they “gain” gas MPG since there is less friction to the engine and the engine is a lot quiet for regular street use.

So… needless to say, I took the fan off my Disco and it was fine for a year. I suspect that if I start off-roading, then I will for sure put the fan back for peace of mind.
Although I hardly used the truck during that year, I did not have any overheating issue with out the fan until now.

Well, a year ago when I was looking for the fan clutch, it was $200 and with the option described above, I decided to try it out the no-fan option.

I will be taking the thermostat off today!

 

One thing you have to remember is that it is much cooler over in the UK. Plus if the PO welded the fan to the fan clutch this could have cause some damage to the bearings in the water pump since Im sure he didnt balance the assyembly (or even come close) with the welds.

You can buy a clutch from Napa for less than 100.00 you will most likely have to elongate the holes to 10mm but that is no biggie.

Part # 215157 (light duty) 71.59
Part # 215158 (heavy duty) 76.69 this will keep it cooler but also be a little louder!

 

Get yourself an aftermarket electric fan kit, jeggs has one in the 5.0 section but it would work for any model of vehicle, mount it and done, if you want to take out the termostat you should cut out the center and put the putside hosing back in to work as a restrictor somewhat so that the water doesn't circulate too fast and not allow enough heat to tranfer from the block evenly. I have seen in chevy and fords where the valves closest to where the water comes in or at the end of the system where water leaves get burnt cause they retained too much heat.

 

Well, I drove around with out the thermostat. After driving for about 15 minutes (and 100 F outside), the truck ran fine with no problems. I continued using the truck a little longer and when I got home, although no bubbling, it was leaking small amounts of water around the water reservoir cap.

Can I buy any water reservoir cap and replace it or I must buy the one at the dealership!

I think the previous owner (or his mechanic) did a good job because when the fan was on, it did not wobble at all.

As far as the water pump, please correct me if I’m wrong but I think it works fine because when I take the radiator top plug out and a rev the Disco, there is good water flow (recirculation) that changes in intensity along with increase RPMs… Is that a true statement about a good working condition water pump?

My intention is not to drive around with out a thermostat. I only took it off to make sure I rule-out the thermostat from being the culprit.

Yesterday I looked around my garage and I found my old fan (with the welded clutch). I am going to put it back but I really think that my problem is not the fan… I think that the previous owner welded it together and probably he never found the real problem. In addition, when I first got the truck, I posted here that it overheated. I replaced a hose and it did overheat again one more time but never found the problem. Short after, the A/C acted up so we never used the A/C… then the fan was removed and the truck was used for less than 300 miles over last year... with no additional problems.
Now that I am ready to start using this truck and trouble shoot its problems, I fixed the front diff and fixed the A/C along multiple other little things.

So… any one out here with an insight on my cooling problem?

 

You could try and use some K&W block sealer, if there was a head gasket problem then it would seal it and then you would know what it was. Have you had the radiator checked out to see if it restricted? It may need to be rodded out or a flush done to it. Another possiblity is that the fins in the water pump have rusted off enough so that they do not push the water through good enough. If you know for sure it is actually overheating then this one is not going to help but check to make sure the sending unit is reading correctly, maybe it says it is hotter than it is. Another thing is to get one of those additives that make the water more efficient (one I can think of is water wetter but there are others).

If it was only heating up while using the AC I'd say the electric fan in front is not kicking in, but it doesn't sound like that is your problem.
so I would have to say that you probably have a blockage somewhere in your system or the pump for what ever reason is not cirulating the water good enough.
Or a blown head gasket (Do you notice an unusually high amount of water dripping from the exaust, or worse water in the oil?) or a bad sensor if the heat is not actually getting that high.

Your biggest problem may become deciding if you are going to replace the things you cannot test in some way to see if fixes your issues. Welding the fan, if done right, should not affect its function. clutches are designed to make the fan quiet compaired the direct drive ones, other than that not much else different.

If it was me, I whould either take to get a good flush done or get the best stuff I could and do it, do the block sealer after that if the flush didn't fix it cause it won't hurt anything if there's not a bad gasket and it is cheap. If still not fixed then replace the water pump cause after that you gotta start thinking raidator then motor which gets costly quick.
I didn't see any mention of leaks except a minor one from the resivor cap so I assume you don't have one. you don't say if you are having to add water or not though, could you clear that up?

 

This is the fault diagnosis part of the Land rover Factory workshop manual:

ENGINE OVERHEATING
Before conducting any cooling system diagnosis: See
Description and operation, Engine Cooling
1. Is coolant level correct?
NO - Allow engine to cool, top up level to
expansion tank seam.
YES - Continue.
2. Is drive belt tension correct?
NO - See ENGINE, Repair, Drive Belt
-Check Tension
YES - Continue.
3. Is ignition timing correct?
NO - See ELECTRICAL, Adjustment,
Ignition Timing
YES - Continue.
4. Is coolant in radiator frozen?
YES - Slowly thaw and drain system. See
Adjustment, Coolant Requirements
NO - Continue.
5. Is air flow through radiator restricted or blocked?
YES - Apply air pressure from engine side of
radiator to clear obstruction.
NO - Continue.
6. Are there any external leaks, from water pump,
engine gaskets or the heater unit?
YES - Investigate and rectify. See Adjustment,
Coolant Requirements
NO - Continue.
7. Are fan blades fitted correct way round, concave
side towards engine?
NO - Rectify.
YES - Continue.
8. Is viscous unit operating correctly? See
Description and operation, Viscous Fan
NO - Renew. See Repair, Viscous
Coupling, Fan Blades, Pulley and Fan
Cowl
YES - Carry out a pressure test on radiator cap
and system. Check thermostat type,
operation and correct fitting See Repair,
Thermostat
If pressure test leads you to suspect coolant
leakage across gaskets, go to check 11,
otherwise: Continue.
9. Are the air conditioning fans operating correctly?
See Electrical Trouble Shooting Manual.K5
NO - Rectify.
YES - Continue.
10. Is temperature sender and gauge giving
accurate readings?
NO - Substitute parts and compare readings.
YES - Continue.
11. Carry out cylinder pressure test to determine if
pressure is leaking into cooling system causing
over pressurising and loss of coolant.
If problem is not diagnosed, check the coolant system
for engine oil contamination and engine lubrication
system for coolant contamination.
If the coolant only, or both systems are contaminated,
suspect cylinder head gaskets or radiator.
If only the lubrication stystem is contaminated with
coolant, suspect inlet manifold or front cover gaskets.

Viscous fan info

The viscous drive unit for the engine cooling fan,
provides a means of controlling the speed of the fan
relative to the running temperature of the engine. The
viscous unit is a type of fluid coupling, which drives
the fan blades through the medium of a special
’silicone fluid’ injected into the unit during
manufacture.

Operation
The viscous unit consists of two principal components:
An inner member 1 which is secured to water pump
spindle and is driven by the fan belt.
An outer member 2 which has the fan blades
attached, houses the working parts and is driven
through the medium of the viscous fluid.
The inner and outer members have interlocking
annular grooves machined in each, with a small
running clearance 3 to allow the silicone fluid to
circulate through the valve plate 4.
The unit also contains a valve 5 which is controlled by
an external bi-metal thermostat 6.
Starting engine from cold
During the time the engine is at rest the silicone fluid
drains down, half filling chambers A and B. Thus when
the engine is first started sufficient fluid is present in
chamber A to provide a positive drive between the
members, as is evident by the initial noise of the fan.
However within a very short period of time, after
starting the engine, the fan speed and noise will
decline indicating that the fluid is being centrifuged
into chamber B (as seen in RR3757M) causing the
drive to slip.

Hot conditions
When operating in high ambient temperatures or
when stationary in traffic, the bi-metal thermostat will
operate and open the valve port between chambers A
and B.
Opening the valve (as shown in RR3758M) allows the
fluid to circulate between the two members, causing
the unit to couple, thus increasing the fan speed and
cooling effect.

 

CronicJoeBlunt, thanks for your help/ideas…


I hate to tell you guys that I put back the mechanical fan and the PROBLEM PERSISTED! Of course, as mentioned before, is not as evident now and I could even drive the truck for small trips with no problems.



1. No but I did a complete flush twice… I will do it soon
2. I doubt this happening since there is significant water recirculation unless… watching the water at the top of the radiator is not a good indicator.
3. Nope… it does acts up with out A/C use
4. Could be… I have being contemplating this but up to this morning, still no sign of head gasket problem (no milky oil on engine oil cap, no oil residue on coolant, no need to add coolant, no water on tail pipe)
5. I’ll take your advice
6. Sorry, I failed to clear that up earlier… well I answered that on this post on #4
7. Thanks for the insert of the workshop manual. I have a CD called “Range NAS” and I had read all and carried out all that section except:
• Checking the timing. (Since I don’t really know the truck, I will do this next week)
• Carry out a pressure test on radiator cap (I will buy a new cap)
• Carry out cylinder pressure test (Hmm, I guess I will get to that after the above)


Do you see a good troubleshooting lead just by the fact that WITH the thermostat on, the water reservoir will bubble a lot and while troubleshooting with the radiator cap off, the water will shoot up AND with OUT the thermostat on, I will have no bubbling and not water shooting up from the radiator… just a leak from the reservoir cap?

I was thinking that the reservoir cap WILL intentionally leak water if the pressure is exceeded so with this I can not assume the water reservoir cap is the culprit… right?

 

Radiator caps are designed to allow overflow depending on the pressure in your cooling system.