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Cooling saga - advice needed.


Accelerating Away
Afternoon all.

About 2 months ago the landrover (series 3, 2.25 diesel) ran very hot. I was hauling wood on a very hot day so thought little of it. Then last week it ran exceeding hot, near the red. Got it home and let things cool a bit. Then had a look in the rad - low on coolant, of course. Then noticed the lower pipe into the heater matrix had a hole.

Problem solved, I thought. New pipe fitted. New coolant. Bleed matrix (bit of a faff to say the least), and out for a spin.

Up near the red line again, but great heat out of the blower! So matrix air lock sorted. Suspected I had an air lock else where. So, burped the system (makeshift funnel jobbie), and got some bubbles. Out for a spin. Up near the red again. Then gauges died. Got home, sorted out electrical fault while the engine cooled. And set to burping the system again, squeezing hoses, etc, but no bubbles.

No leaks anywhere. So, I’ve flushed the system. Filled. Run for a few minutes. Flushed again, and refilled (heater matrix closed), and optimistically thought I’d be on to a good thing.


Rad hot at the top, cold at the bottom. Feed pipe into the top is hot, outlet at bottom cold, and gauge near the red. Guessing thermostat is ok due to top pipe being hot, and able to move fluid through it when engine running by giving it a good squeeze or three. Did notice that coolant is not moving in the rad when engine running and warm (hot).

Fitted a new rad last year, and just filled up and drove, no problems.

So, is my water pump knackered?

The vehicle usually runs the lower side of the ‘N’ on the gauge.

Also, how much damage have I done to my engine with all this running hot? If any? Anything else I need to look out for?

Been a long day!
Yes, as above, don't assume running hot is anything to do with the engine.
Clearly there are several issues that have all sprung up at the same time and come together to muddy the waters so to speak.
Be certain your gauge is correct via the voltage regulator and be sure the sender is ok.
If your top hose is hot, i'd say the stat isn't stuck shut, but it's a cheap bit of confidence to swap in a new one anyway.
As for the damage to your engine, probably nothing really.
Most cooling is done to the bottom end (the fragile bit) via the oil. The water jacket just scrubs heat from the cylinders, which can upset the rings and the head gasket etc, but if it works...well then it does. Might have taken some milage from the overall longevity of the engine, but I doubt you'd notice.
T-stat housing should be at stat temp (or gauge temp anyway).
Bottom of radiator should shed 40-45 degrees F versus the top. 180 down to 135-ish.
Short of that, look for vacuum leaks and retarded timing - closed points or seized centrifugal in your distributor. Don't use factory timing specs, as they're too far retarded for modern fuel.
Appreciate all the replies, gentlemen - thank you.

Will check gauges, etc when I can get back to it at the weekend.

Think it's going to be a circulation issue as bottom of rad is cold, as in ambient temperature, while top is hot.

Will try everything, including the whole airlock thing again while I wait for thermostat (no harm changing it - its at least 15 years old 😀 ).
The rad being hot at the top and coolish at the bottom makes me think its reduced coolant flow, so this could either be the pump not pushing coolant round the system or some restriction in the circulation.

You can get an airlock which will restrict flow, so perhaps just bleed it once more and burp any air out before delving too deep.

Lets assume the pump is OK for now as thats the hardest job. :whistle:

Most likely culprits to restrict coolant circulation are a faulty thermostat (take it out and run the engine and you will soon be able to tell, or test it in a pan of water on the stove) or a build up of crud in the block or radiator.

Once you have tested the thermostat (and if its good), run the engine with a dishwasher tablet as FTD says and then reverse flush the engine and rad.

Once you are fairly sure its clear and if its still the same then look at the pump. I've heard of some pumps that are running fine (bearings good, not leaking) but the impeller has rusted away.
Pump change isn't too bad, literally 9 bolts, harder if it has a shroud fitted.

@Fulltimedad thanks - just picked up some dishwasher tablets.

@mikeau thanks for this - it seems like a solid plan of action, and along my line of thinking, also. I'm going to have another go at the weekend. Hopefully the thermostat will have arrived by then and I can swap it out while I'm in there..

While I was forking out for delivery, etc. I decided to get a new water pump, too. Logic being I have it if I need it while trying to sort all this out, and if I don't its there on the shelf for when it inevitably needs to be done - there is a kind of logic in there somewhere.......

@Big Sandy - "Pump change isn't too bad, literally 9 bolts,"

I suppose in Series Landrover terms its all pretty relative.......spent an hour trying to shift one bolt last weekend....then it spiraled off into other things! Multiply by 9 and you have the fear of god put into me :whistle:
Pump change isn't too bad, literally 9 bolts, harder if it has a shroud fitted.

I know, but...

Screenshot 2024-06-12 at 09.01.36.png
These old iron engines can take a serious amount of overheating with no permanent damage. Obviously its not advisable but they are not like modern engines. Sort the cooling out and if you feel like it check the head bolt torque just in case but I doubt there's a problem.
@LightweightV8auto will do, but think they will be ok - replaced last year when i did the new rad.

@Big Sandy I went for the 82 - can get pretty nippy here in the Irish Midlands in winter (not a huge amount better in summer if this year is anything to go by), so figured the extra bit of warmth wouldn't do any harm.
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