Thread: More over heating

Thanks Booney.

I have given the google thingy a go and still I am not all that happy with the results so far as a good description of what i am in for. I have the RAVE and a bit of other stuff.

From the rave for overheating :

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 system is contaminated with
coolant, suspect inlet manifold or front cover gaskets.

I am also disappointed with the advice for draining the system and refilling it.

The advice in the rave if followed scrupulously still seems to leave airlocks in the heater system. various posts recomend removing a plug in the plumbing to the heater and refilling with the disco on a slope (front up hill)

following the RAVE procedure doesn't do it and following the advice in this forum doesn't do it. I have managed to get rid of the air bu undoing the top pipe to the heater inserting a garden hose into that pipe ( flow toward the heater) and waiting 'til I have full flow coming out of the engine side hose. I quickly reconnect hoses and it seems to get rid of all the bubbles.

If I don't do this I get gurgling in the heater hoses and no warm air...or very little when I turn heater on.

Some advise me to make sure I refill with heater turned on. On my disco 1 1999 with a 3.9 I cant see what difference that would make as mine does not have a water valve. I have physically checked the entire length of the pipes to the heater radiator in the heater box and the system in my disco has heat all the time which is modulated by the hot cold flaps in the heater box.

So I guess if you can see you have a heater valve in the line to the heater box by all means turn it on when filing the coolant system otherwise it makes no difference.


Service repair no - 26.10.01
Draining
WARNING: Do not remove expansion tank
filler cap when engine is hot. The cooling
system is pressurised and personal
scalding could result.
See coolant requirements before refilling system.
1. Remove expansion tank filler cap by slowly
turning it anti-clockwise, pause to allow pressure
to escape. Continue turning it in same direction
and remove.
2. Remove radiator filler plug and ’O’ ring to assist
drainage.
3. Disconnect bottom hose from radiator. Drain
coolant into a clean container. Reconnect bottom
hose, re-tighten hose clamp.
NOTE: It is not possible to drain all coolant
retained in heater system. It is not
desirable to flush through system, after
draining.
4. Remove engine drain plugs, one each side of
cylinder block, beneath exhaust manifolds. Drain
coolant, refit and tighten plugs.
5. Pour correct solution of water and anti-freeze
into expansion tank until radiator is full.
6. Start engine, run it until normal operating
temperature is attained, topping up as
necessary.
7. Refit radiator filler plug and ’O’ ring, with new ’O’
ring if required. Tighten to 6 Nm.
8. Fit expansion tank filler cap.
9. Allow engine to cool, check coolant level. Finally
top up expansion tank until level reaches seam
of expansion tank

Ok so in another thread they recommend checking the viscous fan .

Given I don't have even the slightest hint that a head gasket is blown but I do loose pressure when pressure testing I am still plugging away at the coolant system eliminating everything there. Top and bottom radiator hose off and full flush and clean of radiator. Likewise flushing the heater radiator and the line in through the inlet manifold box.

The barr's leaks stuff gets into everything. Verry sorry i used it but I was desperate and a long way from home. I should have got out the thermos and had a long rest before doing anything.

bars leaks blocks up the radiator check the front of the radiator mine looked like abirds nest replaced radiator runs perfect even with air on 40deg outside in sydney riverstone radiators do a1 recors

thanks redmon

checking viscous coupling on fan is also a difficult thing.
Various methods discussed in forums have no definitive check.

Spinning it by hand on a cold engine should show some resistance. running engine just after start up should show a fair gush of air against your hand if you hold your hand just above the alternator on a disco 1 with 3.9 engine.

My experience is that when the engine is at operating temp there is not all that much difference in the volume of air pushing past the alternator.

I have compared my coupling with a spare I have and both seem about the same.
If there is signs of leaking fluid from the coupling then thats good enough reason to replace it. If the coupling is seized then the problem would be over cooling not overheating. My problem is overheating so seized coupling is not an issue.

If the coupling will not activate and the fan only freewheels than that will cause overheating. That means either the fluid has run out of the coupling ( leaks) or the valves inside the coupling are not allowing the fluid to run to the rear. How to check??? there is no simple way of absolutely eliminating that as a possibility.
It is fair to say ,though, that if the engine is hot and lots of air is being blown from the fan over it then the coupling is working.

Some one suggested getting a rolled up newspaper and gently brushing it against rotating fan with engine at operating temp. If the fan slows down then unserviceable coupling. My problem with this is that if the temperature sensor on the front of the coupling is coolish thats exactly what should happen . The fan is a thermostatically operated device. If the thermostat is operating correctly the fan will be decoupled from the engine until the thermostat on the front of the coupling warms up.

The only absolute test procedure I can think of is to have a device that spins up the viscous coupling then heat up the thermostat with a heat gun to its specified temp and see that the coupling engages.

So if anyone has an absolute certain way of testing the viscous coupling I would love to hear it.

The RAVE offers no test procedure and only a replacement in the repair section.

I have now pumped a couple of litres of air from the header tank through some blue test liquid. No change in colour.

I have puffed in a small amount of the used liquid through a straw just to reassure myself that the liquid is in fact ok and that the CO2 in my breath turns it yellow.

So I was told there was a small leak in the head gasket when I got the mighty disco. That was diagnosed by a mechanic unknown to me .
The symptoms of a blown head gasket are.

I bubbles in the coolant when looking into the header tank with engine running.

2 overpressurizing of coolant system with some blow by of the header tank cap.

3 water in oil as evidenced by milky deposit on dipstick, inside of oil filler cap, on the rocker gear when viewed through the oil filler cap.

4 some water in bottom of sump evidenced by loosening sum plug and letting about a quarter of a cup of oil run into a glass jar. Holding jar up and looking for water at the bottom ( this could also be caused by condensation over time so best done some time soon after an oil change.

5 blowing air from header tank through CO2 detector fluid and seeing fluid turn yellow. Any combustion getting into water will contain CO2, however small the bubbles, that will increase the CO2 concentration in the header tank.
The indicator fluid seems to take about 1 liter of breath @5% CO2 concentration to turn completely yellow. Best to test header tank gas with engine running ( so if the leak is tiny ..so tiny you can't see bubbles) you will get a continuous stream of CO2 through the fluid.
Atmospheric CO2 is ,04% so it will take a huge amount of air through the fluid for it to turn yellow with no combustion products in the coolant.
For it to be as much as in your breath , 4%, a couple of litres of air from the top of the coolant tank will turn it yellow. Combustion producer 12-15%CO2 thats about three times as much as breath . But if the leakage into the header tank is small it could take quite a while for the gas in the top of the tank to reach that mark and it would smell very distinctly of exhaust gas is my guess.
Any CO2 above normal atmospheric levels must mean its getting past the head gasket. But testing for microscopic levels is something this little red duck is not up for.

6 pressure test the cooling system. if there is a head gasket leak you should loose pressure through the hole and blow water into the cylinder. I used an adaptor on top of the header tank and found it very hard not to loose pressure through that adaptor. U used a standard brass gas reducer fitting so i could connect my pressure tester to the brass radiator bung . pumped it up to full operating pressure 15psi and loose at the rate of around 1/2 psi /minute. That was me pumping air into the top of the radiator and compressing the air out of the header tank. If I start with by filling header tank to the top after connecting pressure tester then no loss of pressure untin I hit 15psi then water dribbles psat header tank relief valve. . The header tank relief valve did not seem to relieve but water dripping past indicates all is well. .

7 differential cylinder head pressure test. Using the same technique used on aircraft and a standard differential pressure tester. This gadget gives you an indication of the overall condition of the rings and valves. If there is a head gasket leak you will loose pressure and get bubbles into the header tank. You can work out which cylinder is the problem because it will be substantially lower in pressure than the others. Air whistling into the exhaust indicates valve seat problems on the exhaust side , air whistling into the inlet manifold indicates inlet valve problems. and the sound of air whistling out of your dipstick hole means there is blow by the pistons. Its a great gadget. Use it according to instructions on the packet. aircraft spruce sells them http://www.aircraftspruce.com/catalo...rs_orifice.php

I tested mine by driving until the temperature started to climb then I pulled over and tried to move the fan, if working correctly the fan should be locked solid, mine could be spun fairly easy.

Thanks Boony I will give it a go