At what temp does car enter hot running mode?
I thought it was 88 degrees c
But when looking for thermostats I see dayco dt18A is for these but is an 82 degree thermostat. Is that too cold?
I see they also have a 92 degree thermo that fits but I feel that is too hot.

**edit . never mind. i took the thermo out of my parts car, tested it and it is working.
then i remembered i had a spare from hen i swapped one before just as a precaution, and tested it, and it works.
so now i know i have 2 working thermostats.
one is waxstat and the other is motorrad.
not sure which i will use.
good to know i have two working ones.
just gotta get some gasket sealer now so i can replace mine.


**People always listing wrong parts is really annoying.
one place lists a 54mm flange thermo as for our cat
Another list a 67mm thermo.....
Why do people make it hard

 

On paper the closed loop is 88 C

radiator low fan mode is 86 C , High fan mode is 100 C

So just above 88 is just right . 92 not too hot as it gives you a margin above 88 to not keep going into open loop

 

Closed loop is somewhere just above 160F

 

ok so.....
I ran the car today without the thermo fans on, and it did warm up (almost to normal) and it ran better.

when i got home i took out the thermostat, see it is clearly marked as 87 degrees c.....
now when testing, i see that it is opening at 60 degrees c.
so it is opening way tooo early...
so this thermostat is less than 2 years old and less than 15000km on it and is dead

put a 2nd hand replacement i had around in and lets see how she goes....

 

What brand was the failed thermostat? I’d like to avoid that one in the future

 

honestly can’t tell you the brand. i wish i knew. Only marking on it is JDA and 87c
it was suppled to me by one of the biggest jag parts places here and was sold to me as an OE replacement.

 

Ok, so, update......

Few days since changing the thermostat and its driving like it never had a problem.

Crazy how bad it was running from a stuck thermostat.
Esp as It was running bad regardless if it had just been started or if I had been driving for half an hour

 

Great news. Thank you for chronicling this for the rest of us.

 

Hope it was really just the thermostat. In my experience, the car would behave like the problem never happened but might return some three to four weeks later. Never seen any permanent solutions for similar situations.

 

will keep updated on what happens

 

so update.

2 weeks on from thermostat replacement and car purring beautifully still.

 

so almost two months on since thermostat replacement and all is still great.
so it seems that when the jag is constantly being run cold it messes up the way the ECU tries to balance the air fuel mixture to the point where the car does not like to run.
a little bit running cold it boosts the fuel.
but obviously over time when it constantly fails to warm the car it is just trying more and more to warm it.
not sure if the car was constantly running richer and richer or just running rich for an extended period slowly makes the car run worse and worse.

 

Spud,
pleased to hear that all is still well, and that in the end the fix wasn’t too painful.
As I was re reading the thread, I watched your video clip again, which was before you changed the crankshaft position sensor.
A tangential point given you have now fixed the problem, but I didn’t notice the rev counter twitch as you turned the ignition on. From the dark recesses of my mind, is the needle not supposed to twitch up to about 200rpm, and if it doesn’t, it indicated a CKPS problem? Not relevant to your problem any longer, but I am now wondering whether I have mis-remembered this, or it is an old wives tale.

 

The 87 C marked thermostat is too close in manufacturing margins to the coolant temp sensor 88 C in it's margins to be in closed loop , the ECU connector has to be in good shape also

I noticed in reading someone a 92 C thermostat ?

The thermostat temperature regulation should have nothing to do with the radiator fans coming on and the subsequent coolant temp going back into the block

Fans 86 C ( low mode ) and 100 C ( high mode )

 

Starter rotation 300 RPMs ?

 

it is before you crank, just as it has the ignition switched on.
I could be imagining it, but it rings a bell.

 

On my car with the power off both the speedo needle and the tacho needle are at a rest position at less than zero. When the IGN is switched on the tacho needle moves to about the 200 rpm position and the speedo needle moves to the Zero position. The other indicator needles also come alive.

Cheers,
Jeff.

 

it did jump to about 200rpm when attempting to crank. not with ignition on but after cranking started where it stayed whilst trying to crank.

during my trouble shooting i did replace the ckps just to see. no difference was made from when i did that.