Thermostat Working OK??

The 'stat works, I know that because until she reaches an indicated 70 deg the rad hoses are cold. After that when the 'stat opens the temperature fluctuates slightly but remains at approximately 70 deg.

I know it should run at 90 because everyone tells me so and the new stat is stamped 88 deg; but does it need changing or is the temp sender faulty? Would a fault be shown on a diagnostic check?

Any advice welcome before I place the order with "Shop4Parts" @ £47 + tax.

Rob

id say change it it must be worn out and opening too cold

I would 2nd that, just done mine...easy job!

Just posted a similar reply on another thread but I experienced the same with my 1.9JTD - turns out my gauge reads incorrectly as confirmed by temp reported by ECU using ODB reader. I am also sure my stat is ok as temp drops slightly at about 85deg when stat opens and cold water from radiator enters the system.

diag wont show faulty stat - but will show temp in case guage wrong

not so easy on a jtd as a TS

Try to measure the actual temperature of the water. The indicator may by showing 70 but in fact it can be 88. Heard that from couple of friends it happens sometimes.

Every few weeks we get a post like this. It's always the thermostat.
When it works properly the temperature will climb steadily to 90c and then stay there.
If yours is going up to 70 and the falling rapidly, It's faulty. The unit is sticking then allowing too much cold water in before sticking again.
I can't understand the debate. It was one of the first 'known faults' published and sooner or later you'll need to change it.

My 1.9 JTD used to go up to just past 70 C before it dropped slightly (thermostat opening) and would then sit around the 70 C mark. I had it checked by the dealer and they said the temp was at the correct temp (90 C) on the diagnostic machine - just that the display was wrong.

I have recently changed the thermostat as I was changing the radiator and the temp guage now goes up to just past 90 C before the thermostat opens and the temp drops slightly and it then sits around 90 C.

I have since checked the old thermostat and it only opens once it is over 90 C, so it must be the temp sensor (part of the thermostat) that was faulty and making it read 70 C.

As I said, if it drops it's sticking.
The diagnostics machines can't be any more accurate than the the sensor tells it. The only thing that can be checked is whether the gauge is the same as the machine. Both can be reading a faulty sensor.
Mine opened at 70 and dropped like a stone. Repaired; it just creeps up to 90 and stays there.
Back to my main point... If it goes to 70 and stops (or falls) it's the thermostat. Always is. Don't bother with any other testing.

Just ordered a replacement 'stat. On a long run it sat at just under 70 degs; the only time it got near 90 was on a long incline.

Rob

i tried to get mine done at thorobred last week with the service, but they said its working fine: 'pressure tested' and the diagnostic reads a temp of 92c while the needle on dash stays at 70 or crawls to 92 and drops again. they changed the temp sender/sensor as I was unsure the engine fan was kicking in on time, they said the temp sender wasnt triggering the fan and the new sender triggers the fan at 88c?
shes running much nicer but that would be the service!

Thanks everyone for advice, the 'stat has been changed; temp now at 90 deg or just a fraction under. I also cleaned the EGR valve; despite the "low temperature" she was running at there were only slight deposits of soot, which makes me think it was the sensor that was at fault.

A good clean with carb cleaner and she does seem to be running better; the trip to Essex tomorrow and Exeter on Thursday will tell!

Rob