Hi there would love some help with a diagnosis. I have had my 2.5Dt for a little over 8months . I would say she's be very reliable but are near a grand worth off parts and labour from me and garages she not been the cheapest of cars but as a competent mechanic I refuse to part with her as she's also got something about her I am told its a Landy thing. Anyway

After a long drive to Andover over a week ago she over heated shortly after coming off the dual carriage way. To the point she lost most of her water I think through the header breather as their appears to be no other obvious leaks. She did the same last night after a stretch doing 70 odd fine but temp needle occasionally goes a third over normal mark whilst cruising. Once in town at slow speeds she over heats and dumps two litres of water.

Now the other parts to this are the viscous fan has little resistance and my friend has told me after a running there should be . I can physically stop it with my hand on idle after and hours drive. Also the other day she took ages to warm up. After a quick look and feel under the bonnet I discover the rad pipes both sides where empty. I squeezed them with the cap off the header and when I started her after several miles they refilled and then she started to over heat again.

Returning to when she overheated the other day she went straight to red within the blink of an eye. During being very hot the heater went cold which was odd

So I am thinking

Head gasket

Faulty thermostat

Airlock

Faulty water pump

Or something else

Anyway at a loss now so would appreciate any direction

Ment to add she runs fine pulls fine rough on start up but down to glow plugs me thinks as after several heats she fires up perfectly

I'd love to take the poll off this thread that I didn't mean to put on lol idiot

Sounds like exhaust gasses getting into and pressurising water to me!

I had a H/G fail twice on a 3.9 V8 classic and it showed very similar symptoms and would idle up to temp and run for ages without any signs. Always lost water when it had been under load and eased off. Logical when you think about it as that heat build up is no longer being cooled by high rotational speeds of the fan (a good plus for electric fans!) Not sure how prone to gasket failures the diesels are, but better it's a gasket than head or (worse) block!

You perhaps need to run up to temp and bleed off any air to be sure it's not just an air lock and there are tests I believe you can do on the water. I had mine done by an engine specialist first time, but when it went again I did myself. Not a difficult job if you're handy with tools, but allow plenty of time as it takes a while taking everything off! I don't relish the thought of ever doing on my new (to me) HSE as there's even less space under the hood!

I'm yes could well be still unsure why blower when cold and then the pipes went empty. Also if the fan I failing then surly high speeds would cool it until one slows. Also she remains cool on short journeys 10 mins or so and she's does not heat up on idle even after 15 mins she's still on cold

Could this be the water pump impeller coming off problem??

Cheers

Jerry

Previous owner could have removed thermostat to hide or as a dirty-fix for overheat. No heater and empty hoses/top half of rad are symptomatic of air locks as the air expands and forces water out via expansion tank. The concern is how the air is getting there - could be a leak when air is sucked in as she cools or, more likely exhaust gases under pressure from cylinder pushed through between head and block via faulty gasket.

I wasn't suggesting viscous fan was faulty, just the very nature of this design allows a 'spike' in engine temp when dropping off from high revs. The engine slows and so does the fan, but heat is still building in the block and takes longer to dissipate than it does to take foot off the gas. Overheats are more likely when motor has been running high sustained revs for a while and then suddenly eased off (like exiting a motorway onto a traffic queue at one of those roundabouts they always stick at the top of the slipway!). Next time you are on a motorway/dual carriage way, drop the speed off slowly and earlier before entering suburbia and see if the same thing happens...

Before you spend any money you want to get a sniff test on your coolant. These engines don't like being overheated and you could have a cracked head. If it passes the sniff test then you need to check out your cooling system.

The viscous fan should be stiff to turn before you start the engine. Then, at tick over before the engine warms up you should be able to stop it with a rolled up newspaper. Once the engine is hot it should shred the newspaper.
If your stat was faulty or has been removed then your temperature gauge should hardly get out of the blue zone, if everything else is working well.
Some P38s were fitted with water pumps with plastic impellors that can either come off the shaft drive or even break up inside the engine.
If the rad is blocked or silted up inside then you will not get good cooling at lower road speeds. Also the design of the rad relies on a central baffle at the top forcing the hot water down into the rad to be cooled before it leaves at the top on the other side. If this baffle has failed then the water can just pass across the top of the rad.

So - check your viscous fan first but regardless of what you find don't stop there. Get the rad out, give it a good wash out inside and out and try to run a pebble or marble across from inlet to output. If it rolls out then the baffle has gone. Check the stat in a pan of hot water. Take the water pump out and check for damage.

If you can stop the fan with your hand after an hours drive it is knackered change it. Your problems will probably go away. But it maybe a good idea to take a look at the water pump aswell.

Right we'll on further development she has now developed a tremendous shudder or vibration. It's worse between thirty an fourth. Changing gear helps reduce but still there even if you dip the clutch and wait for revs to drop. Is it related. Or desperate issue. Going to get the lads at Sutherland to check wheels room I had a buckle in one wonder if it's got worst or weights come of but was wondering if gasket is going and engine running bad is causing problems

For God sake. After a new clutch. New alternator New hubs both side at the front new crank dampener battery nearly 1200 quid later I am at the point where I have had enough.

Just finish rebuilding a hydro locked disco for my mate with a bent con rod now loads to do on my 38. Lol

rangeyroamer said:

Right we'll on further development she has now developed a tremendous shudder or vibration. It's worse between thirty an fourth. Changing gear helps reduce but still there even if you dip the clutch and wait for revs to drop. Is it related. Or desperate issue. Going to get the lads at Sutherland to check wheels room I had a buckle in one wonder if it's got worst or weights come of but was wondering if gasket is going and engine running bad is causing problems

For God sake. After a new clutch. New alternator New hubs both side at the front new crank dampener battery nearly 1200 quid later I am at the point where I have had enough.

Just finish rebuilding a hydro locked disco for my mate with a bent con rod now loads to do on my 38. Lol

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You have already found the viscous fan is faulty, look at that first.
You could use the aircon fans for cooling and chuck the viscous, I have a mod for this.