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Webley1991

Well-Known Member
What is the normal operating temperature of the 2.25 Diesel series engine?

Last weekend I got stuck in a traffic jam during the hot weather. The dashboard gauge rose to just below the bottom of the hot section. I pulled over and measured the engine temperatures with a non-contact thermometer. I got a reading of around 90c (194f) from the block and 85c (185f) for the head. The cooling system is standard apart from having a 4 blade white plastic fan from a 2.5NA engine fitted.

I took it out again today and got readings of around 80c for the block and head. The gauge was in the upper "N" range. A few minutes later the needle dropped again slightly, which I assume was due to the thermostat opening.

I am aware that the standard gauges are not very reliable. I also have some digital gauges with the probes attached to the top and bottom of the radiator. I have never got round to fitting an aftermarket gauge with a sender in place of the original.

I have not driven many times before in weather as warm as last weekend. The engine was completely rebuilt when installed, so the cooling system should be clear of sediment or blockages.

Are those temperature ranges normal?

Thanks for any replies.
 
My 2.25d sits on the bottom of the N when up to temperature. If the outside temperature is over 25 degrees and I'm going up an incline or have all the family loaded in and pushing 45-50mph for a while it can rise to midway or rarely above midway. It never gets near the red. I would thoroughly flush the system and heater matrix too and mix with a 50/50 antifreeze solution.
 
Engines tend to run 90-100 deg C but can go to around 105 without trouble. Hotter water shifts more heat through the rad. The pressure cap tells you the max as its designed to raise the boiling temp. I would expect the water in some parts (ie the cylinder head) to regulalry be over 100 C otherwise the system could run withut a cap, which it can't. As the rad caps are in PSI you may find the graphs for temp are in F. (212F is boiling) If the water is going into the bottle then its lifting the rad cap, some of that will be expansion, but the pressure still has to be there.
 
Thanks for the replies.

I have read that some aftermarket senders can give incorrect readings. I remember the gauge reading lower before the engine was reconditioned. There was no sender fitted when I got it back so I bought and fitted a new one. The dial has always read on the high side of the N. It seemed to rise a bit higher when driving in the recent hot weather. There are no signs of leaks or coolant loss.

I had read that around 80c was normal operating temperature for an engine.

The digital gauges I fitted myself as a temporary measure have probes attached to the outside of the top and bottom radiator hoses under pieces of foam insulation.

I did flush and refill the cooling system with de-ionised water and fresh blue antifreeze last year. When I removed the cap earlier today, the water has started to look very slightly brown again. As both the head and block are cast iron, is this normal?

What readings do the durite type gauges usually give?
 
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There's a lot to be said for this style of gauge (common fit on old tractors). Cuts out a lot of worry and other unecessary thinking!
s-l300.jpg

The oil gauge is great:
s-l1600-2-10.jpg


What more do you need?
 
What temperature is the thermostat that you have fitted Landrover used to do two versions on the petrol 74 deg and 82 degrees offhand cannot recall what was fitted to 2.25 diesel. 200tdi is 88 degrees.
Your temperatures seem fine to me if gauges reading high could be voltage regulator if you have one fitted.
 
When I did my Scotland trip sitting at 55ish on long runs the gauge just touched bottom of red on my 2.25 diesel but then would drop after a while and then go back up again , I thought it was thermostat opening to but was worried it was going to go higher but it didn’t dosent lose water not even sure if any gets in expansion tank!
 
I had the Series out this afternoon. After driving is slow traffic, the needle got to the top of the letter N on the gauge, but not near the red. With the needle at this position, the block temperature was 80c and the head temperature was 75c. This was measured using an IR non-contact thermometer. Outside air temperature was around 19c.

I bought a new old stock Japanese made sender that I bench tested using a multimeter, digital thermometer and mug of hot water. These are the readings I got:

20c - 321 Ohms
30c - 248 Ohms
40c - 188 Ohms
50c - 144 Ohms
60c - 111 Ohms
70c - 85 Ohms
80c - 64 Ohms
90c - 54 Ohms

Below are the readings from the sender currently fitted to the cylinder head. The head did not get hot enough to test the 80 and 90c readings, which is a good sign. Between 40 and 70c, these readings seem very similar to the new sender I tested. The 30c reading doesn't make much difference as that was too low to register on the original gauge. I am hoping that this test rules out any problems with the sender without needing to remove it.

30c - 387 Ohms
40c - 194 Ohms
50c - 147 Ohms
60c - 115 Ohms
70c - 85 Ohms

rob1miles said:
There's a lot to be said for this style of gauge (common fit on old tractors). Cuts out a lot of worry and other unecessary thinking!
Click to expand...

How easy are those copper capillary type gauges to fit? It seems like it would be a pain to route the capillary through a Series dashboard and bulkhead. Fitting on a tractor seems like it wouldn't need as many bends in the tube.

I am looking for a way to fit an extra sender for another electrical gauge but still keep the original working.
 
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rob1miles said:
There's a lot to be said for this style of gauge (common fit on old tractors). Cuts out a lot of worry and other unecessary thinking!
s-l300.jpg
Plenty of holes in series dash and the pipe is easy enough to route and support in a couple of places, rubbered P clips are good.
Click to expand...
 
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The tractor style gauges (ie 95 go 5% no-go) come in mech and electrical versions. Having driven cars with the caplilliary gauges they are a bit of pain as you have to be carefull not to damage the line. It usually starts somewhere near the front and winds its way all the way to the dash, and if you move the dash you have to be very carefull not to kink it. The trouble is they are sealed so if you take the dash out you have to leave the calipillary gauge behind, you can't take the pipe off. Because the engine moves you can't clip the capilliary too tightly so that leaves it hanging and vulnerable.
 
The gauge is designed for 10V if it is getting say 12V -14V with running engine that will make a significant difference to current flowing and gauge reading.
 
These were the readings I got from testing a brand new Cambiare (Italian) branded sender that I ordered from my local spares supplier. These seem to be notably higher than the first one I tested. The manufacturers part number for this sender is VE718038.

20c - 793 Ohms
30c - 544 Ohms
40c - 364 Ohms
50c - 251 Ohms
60c - 173 Ohms
70c - 122 Ohms
80c - 95 Ohms
 
Readings from a known good unit awhile back . your new one seems too high resistance.
Temperature 13 15 18 56 100C
series sender 460 385 323 118 56
 
I think I have read posts before which said that these sender readings can vary despite them being supposedly an equivalent part.

That is what their system recommended. I though it would be worth buying another to compare the readings against the two I have already tested.
 
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Have you looked inside one of the senders? Its very low tech, the chances of it even being repeatable within +/- 10% must be very slim.
 
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