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How warm should the water be ??


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Been looking at the output from my EFi ECU.

It would appear that while on the move my water isn't getting above 77 degrees Centigrade.

I replaced the thermostat recently and the one I received was 82 degrees opening temp.

I believe it should have been 88, but I just needed something that would actually close at the time as I was running very cool.

What should I be aiming for?

(I'm happy to replace thermostat again...)

For info., it's an old RRC 3.9 EFi engine....

Also interesting is that the Durite tacho is way off.... Ticking over at 760 is RPM is reading 1000 ish on the tacho.... 3.5k on the tacho is only 2.3 on the system direct from the ECU.... (Yes the switch on the back is set to 8 cylinders.. and no I don't want a nice diesel instead....) I'm wondering if it's wired incorrectly internally... Doing the sums, looks like it's reading out 6 cylinders but using 8 as a count...

Anyone suggest either an adjustable tacho unit (52mm) or digital one ?

Neil

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Been looking at the output from my EFi ECU.

Also interesting is that the Durite tacho is way off.... Ticking over at 760 is RPM is reading 1000 ish on the tacho.... 3.5k on the tacho is only 2.3 on the system direct from the ECU.... (Yes the switch on the back is set to 8 cylinders.. and no I don't want a nice diesel instead....) I'm wondering if it's wired incorrectly internally... Doing the sums, looks like it's reading out 6 cylinders but using 8 as a count...

Anyone suggest either an adjustable tacho unit (52mm) or digital one ?

Neil

Oh bugger..... just put a durite tacho into mine. I hope it doesn't show the same fault!!!

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Exactly.. What thread type am I talking as no site I've found yet tells you which sender for which vehicle !!

It can't be so hard.....

Edit:

Found a very helpful man at Merlin Racing... Water temperature unit for Rover V8 is 5/8 UNF for any others that need the information.

Neil

Edited by V8 Freak
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Well....

Divster.... The switch had been knocked over and was on 6 cylinders... Tacho was ok other than that.... Juts out a bit on the rear and must have been flicked by a wire or something when I re-inserted the dash...

VDO temp gauge and calibrated sender fitted, as well as new 88 degree thermostat to replace the 82 degree one...

(Not connected the PC back to check actual temps recorded by ECU yet)

VDO gauge now showing car running at approx. 60 degrees when mobile !!

Can someone clarify something for me please.... Are thermostats supposed to open and close during normal operation to try and maintain an optimum temperature?

Have I just had a run of duff thermostats or should I expect to see the temperature hold around 88 degrees ?

Thanks in advance

Neil

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I think this right --------------

the stat should open when it sense the correct water temp which will allow thw coolant flow to the radiator, if the engine drops below the stat's opening temp it should slowly close off, it won't shunt around during normal running to maintain the correct temp, i.e. if engine is at 88 stat opens when it gets to say 95 stat stays open, if temp drops to say 65 stat should close until back upto 88, if your new stat had a vent hole with a jiggle pin in it, the hole/pin must be at the uppermost position,

test the others in a pan of water with a thermometer & bring the temp up to find out when the suspect stats open.

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Is what I was thinking Ralph....

But not such a range I suspect....

I would imaging they should close nearer the opening temperature... If not, engines can run well under optimum temperature...

Anyone else have a view ?

Neil

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Well....

Divster.... The switch had been knocked over and was on 6 cylinders... Tacho was ok other than that.... Juts out a bit on the rear and must have been flicked by a wire or something when I re-inserted the dash...

Phew... thanks Neil

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The V8 should run at a constant 88 to 90 ……………….i.e. it should settle at the stat opening temperature. On a decent capillary gauge you can see the stat open ……….. the temp comes up to 90 ish and then suddenly drops back to 85 ish as the stat opens and allows colder coolant to circulate.

Its mighty unusual for a 3.9 to run cool, especially when in a defender. What Rad are you using ? How is the cooling system plumbed in as it is possible to unwittingly bypass the stat (very usual) ………… but the explanation of how this is achieved gets very complex……….

Ian

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Is what I was thinking Ralph....

But not such a range I suspect....

I would imaging they should close nearer the opening temperature... If not, engines can run well under optimum temperature...

Anyone else have a view ?

Neil

figures other than 88 were just a example, not definite figures :rolleyes:

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Can someone clarify something for me please.... Are thermostats supposed to open and close during normal operation to try and maintain an optimum temperature?

Neil

On my 300Tdi 90 with a VDO temp gauge, you can clearly see the thermostat modulating the water temp. If stuck sat in traffic it closes off, the flow as a Tdi idling doesn't produce any waste heat (unlike a V8..). When it gets going again, water temp goes up past thermostat opening temp, then drops back down as it opens and the cooler water from the rad gets added to the system.

On a V8, I would have thought the temp should be more constant, however a m8 had his Astra rigged up to a rolling road and the temp was measured using a IR detector. That clearly showed the thermostat modulating water flow as well.

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Rad is the one that was in there with the 3.5.... Looks standard kit and fits across the whole width of the gap in the 110.

3.5 ran constant temp.

Moved same sender unit over to the 3.9 and it has always run cool.

Stat changed as assumed it was stuck open. 88 degree stat installed and it appeared to be running hot.... Took it out and stuck 82 degree version in.

Connect up the electricery and is was running at 77 degrees, fairly consistently.

Installed another 88 degree stat (managed to drive over the last one and destroy it) and new VDO + calibrated sender gauge showing running at 60 ish. Will connect up electrickery for official number one evening this week.

I'm assuming the new stat is stuck open as there was no evidence of the temp climbing while driving last night.

Temp came up fine on tick-over and fans cut in at the required 88 degrees. (According to the VDO gauge)

Don't believe the stat is being bypassed as temp was holding at 77 degrees previously..... Plumbing all standard...

Ordered another 88 degree stat while ordering other parts onlien last night so will check temps and have another go later this week....

I'll also do as suggested Ralph and boil my collection of stats to see when they are opening and closing, if they are...

Neil

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V8 radiators ---

you've most likely got a ESR76 fitted [upto chassis FA428918 for 3.5 V8 without oil cooler

others are

ESR203 from FA428919 without oil cooler for 3.5 V8

ESR204 upto JA918061 with oil cooler

ESR1678 from TA976036 to TA977127 with oil cooler

ESR3685 from TA977128 with oil cooler

4 litre [3.9] EFI uses ESR3685 doesn't say if it has a oil cooler or not, not sure if the matrix is a different thickness front to rear either.

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