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2.25 diesel Series III 109 running hot when working


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My series III 109 2.25 diesel runs up to just under the red part of the gauge when driving in the current warm weather (30+ C), when working uphill it gets even hotter! Something must be wrong. Any ideas?

As soon as I start the engine (was cooled down to ~33 degrees) the temp in the rad also starts to rise up to 71.5 degrees (71.5C after correction). Needle then sits in the middle where I want it.

Temperature in radiator is measured with a Chinese meter and figures here are after correction (based on boiling water i calculated the deviation it had)

When I start driving some hills in france it will soon raise to just below hot(red) and yesterday after ~20 minutes on the road it was in the red. A clear sign something is to hot :P

What do I know so far:

- The behaviour when revving in Neutral seems 'nice'. Climbs to middle of needle and stays there

- Temp in radiator isn't crazy when revving a bit in neutral (71.5 degrees)

- Driving uphill temp raises into red

- Driving flat or downhill it manages to keep it just under the hot level, just above the top of the letter N.

- Coolant seems 'brownish' might be years old

- top of the radiator is warm, not funny to touch but neither burning my hands. after 30 minutes revving in Neutral.

- lower hose is warmish, not hot, same for top hose, feels cooler than top of the radiator.

- fluid level is consistent the same.

- power to fuel and temp gauge is light green and leads to the voltage stabiliser. Can't be red with multimeter, so likely the old classic stabiliser. Not a replacement LM7910

- sender is replaced by a new one

so far that does make sense. Running without load it sits at ~72C which equals center of gauge.

Then why does it run hot when loaded. It has new oil, oil warning light doesn't come on so there should be basic pressure.

HOWEVER: the oil pressure gauge sits at or just below 2 kg/m2 which is 28.4 PSI. It stays there at any RPM or at any workload. Not sure how reliable the sender and gauge is, could this be related to overheating when working?

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your oil pressure is a bit low going by the guage, not significant on the heat front .

There are 3 major possibles,

1 guage is wrong

2 thermostat isnt working properly

3 radiator is clogged up

what temp thermostat is fitted ? I would start there , you will then have a known datum of water going to rad to check your temp reading against

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  • 3 weeks later...

Well... I'm out of thoughts for a moment. On a normal day cruising, taking it easy... the needle is perfect middle. However up slopes / hills in a hot day will make it over heat. i assume:

- gauge is fine, as it operates perfectly middle in normal slow (<35 Mph) road driving and soms mild forest roads

- thermostat should be fine as it keeps needle spot in the middle, broken thermostat should cause more fluctuating temps

leaves me with a clogged radiator, I bought the 109 a year ago and it had an old radiator with it. So a new one was installed at a certain point. seems the radiator consists of 2 parts. looking at the front 1/3rd part on the left hand seems to be seperate from the other 2/3rd. Is that as expected? As in normal temps the thermostat functions fine only working hard in hot temps the system cannot keep up. So I'd have to assume I lack cooling capacity in my radiator......

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This would be controllable from inside the cab and able to be set for what temp you want. And instead of being dependant on engine revs, this would be flowing as per the water temp alone.

hmmm up hill in 4th might be heavier than in 3rd with more revs on the heating system then.

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yes a normal fan on the original engine. Belt is tight, blades look good. Running rev's standing still doesn't cause overheating (have hand throttle :) :) )

Supprised that my new water already looks rusted after 2 weeks. Refreshed all the water an added 2L cooling fluid to be mixed with water in the system.

Started foaming a bit (running with rad cap off). Will see later on this week if I can still get it to overheat. (doesn't overheat THAT fast, just annoying that it starts heating up after 45 minutes driving hills. Shouldn't do that!)

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The fan is on the right way round isn't it? (Curved blade face should be forward.)

France has better hills than England. What's your altitude?

If the water looks dirty I'd start by flushing it thoroughly, fill and run it and possibly do it again if I thought there was a build up of sludge somewhere.

The proper radiator has tanks top and bottom. Yours does this doesn't it? (Many vehicles now have crossflow radiators with tanks at the side rather than top and bottom. These are excellent - but if the coolant is dirty the tubes start to block from the bottom. All is well until one too many pipes is blocked and the vehicle is stressed)

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I have rad with tank on top / bottom.

Hills are not that bad. Can run up most in 3rd. we're talking hills not mountains yet (although i'd expect it to cope there as well)

will check fan, pretty sure that's fine

flushed water twice in 3 days. Second time still rusty.

Should I fill it with coca cola and leave that overnight???

I've found a bottle of chemical radiator cleaner at a big Carrefour (supermarket). Will try that and thereafter fill it with premixed coolant in stead of mixing concentrated coolant with the 'hard' tap water here.

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ola, flushing the radiator 3 times with tap water. All 3 times the water turns mild brown in ~15 minutes of running. After 3 times filling, heating, draining I used the chemical cleaning stuff, after that another water flush. Now I'll put proper coolant in.

All the times clean stuff goes in, light brown water comes out.....

no (severe) oil/water loss/consumption however.... still leaking head gasket???

recently changed oil, nice black oil, no water found.

when the car starts it gives a plume of white smoke (and plume black if I hit the throttle) for the first 30 seconds, thereafter all is nice.

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it does sound like the water system is a bit sludged up , I'd just keep flushing it through every couple of weeks . There is a block drain as well under the manifolds , removing that and pushing the garden hose up against the hole will help to loosen any crud around the bottom of the bore casting



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I cleaned a cooling system very quickly and easily with caustic soda and water. It made a huge difference tot he heater's output, and would be down not only to clearing the heater matrix but also the block and head, allowing them to transfer heat into the coolant. You just have to flush very thoroughly afterwards - I don't think protracted exposure to such strong alkali would do the water pump a lot of good.

I did have exactly your symptoms with a 2.5 NAD in my 109 while running on a 2.25 petrol exhaust. I think the mufflers are different, and the 2.5 exhaust is much wider, but couldn't say whether the same is true of the 2.25 NAD exhaust. Fitting a 2" pipe with the correct muffler stopped the problem instantly and permanently.

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  • 7 months later...

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