Running hot

[dave88sw]

Hi,

I'm having a bit of a headache with my series 3, 2.25 petrol.  It always used to run with the temperature gauge bang on the middle of the "N" where it should, however, it's been laid up a while and since i've started using it again, the needle is sitting a little above the "N", about halfway between normal and the red zone.  It doesn't appear to rise any higher, even if i take it up a long hill.

I had this happen many years back and that turned out to be a crappy britpart sender unit, so first thing i did was change the sender again (genuine land rover one), i've also changed the voltage stabiliser for the gauges (solid state replacement) but the gauge is still reading exactly the same.

I don't think it is actually running particularly warm, i can hold the top hose quite comfortably and there's no excess pressure there.  So, i'm a bit stumped, where would you go next?  I'm probably going to order a new genuine thermostat and give that a go but i'm getting a bit bored of replacing bits that aren't at fault.

Any suggestions?

Thanks

Dave

[jordan_meakin]

You could use an infrared thermometer to see what temperature it's actually running at?  Have you checked your timing recently?  The next thing is to check for blockages - flush the system, hose pipe on the heater matrix, through the block and the radiator to get rid of gunge.  Careful where the run off goes though!  How's your water pump sound?  

[dave88sw]

I'll try and get hold of a thermometer but timing has been checked and set up following the advice in the third post on this thread:

Biggest trouble being i can't really find definitive figures for setting the timing.  It's currently at nearly 6btdc at idle (its a 8:1 compression head so manual suggests static figure of tdc but it runs much better at 6 before)

It's a brand new radiator and i'm fairly sure there's no build up, in the 12 years i've owned it it's not been in 1 piece long enough to accumulate sludge!!

Water pump is good.

 

Thanks

Dave

[David Sparkes]

My first (and only) thought on this is 'Earth', by which I mean a difference in earth potential at the sender (cylinder head) and the earth potential at the gauge.
There may be other effective ways of testing the status of this condition, but I'd start by connecting a digital voltmeter between the 'casing' of the sender and the earth connection (casing?) of the gauge. I will stress making these connections as close as electrically possible to the components. For instance, clipping the meter to the earth wire that is clamped to the instrument panel is too far away. Similarly, clipping the meter to the exposed thread on a cylinder head stud is too far from the sender.

I'd use a 2.5 or 1.0 volt scale. The advantage of using a digital meter is because you do not know, under fault conditions, which is the earthy end of the circuit, but the negative symbol on the meter screen will tell you, whereas getting an analogue meter reversed will just give you a slight backward flick of the needle.

What reading would I expect?
What reading is acceptable?

I do not know 🙂  Irritating isn't it?
Seriously, if it was mine I'd have to make a judgement, and decide whether to chase better connections (to reduce the potential difference), or think of something else.

Regards.

[dave88sw]

Sorry for the slow response, I do appreciate the suggestions. 

I've just changed out the thermostat, for some reason it had an 82 degree one, I've stuck a 74 in. Unfortunately it's still getting a little warm.

I'm fairly certain it's not an earth issue, it has multiple earth straps on the engine and the gauge earth is good and clean.

I did however pull a couple of spark plugs earlier and they're very pale so that might explain it if it's running fairly lean. 

 

Cheers

Dave

[lo-fi]

Isn't this a fault that can be caused by a faulty 10v stabiliser? Having been laid up, I bet its furred up inside and not giving the correct reference. 

[dave88sw]

I've already changed it for a solid state one in the hope that was the problem but no change. Thanks for the suggestion though

[Jon White]

I found a 10v solid state one was too high a voltage - I believe the old mechanical one is a “nominal” 10v which in reality never really is 10v. I swapped mine to a 9v and it’s much better now.

Jon