Advantages of running a cooler thermostat:
... Is getting coolant flow happening sooner.
Coolant entering the radiator at 195' ... leaves the radiator at about 180'
Coolant entering the radiator at 185' ... leaves the radiator at about 170' ... which gives the thermostat some cooler temp liquid to play with when dealing with the hot liquid temps generated by the engine.
............ all depending on cooling system efficiency of course
As the radiator is a heat exchanger ... not a refridgerator that forces temps down to a minimum preset temp.
Lower temp thermostats are NOT an overheating fix ..... but they can be used to gain a
slight advantage in maintaining a constant operating temp ... depending on operating conditions.
Its nigh on impossible to get the 4.0l XJs running temp down to a
constant,
low temp due to the size of the radiator and the small engine bay.
The best Ive managed is a
constant 195' in operating temps of 30' to 110'+ for the past 12mnths.
That is with;
A 2row copper/brass radiator, (always used 2row factory aluminium/plastic before)
30/70 coolant mix ( less actually - due to local ambient temps),
Separate AW4 oil cooler,(always relied on the useless factory system before)
Heavy duty fanclutch,(always fitted a std factory one before)
1/2" bonnet spacers & induction blocker.
.... and a thermostat that is 1/4 open at 195' ... and fully open at 205'.
Its sold here as a 195' thermostat but performs probably, similiarily to what a U.S. 188' thermostat does.
By comparison ... the factory thermostat starts to open at 195' and is fully open at 220'.
The XJ thermostat is NOT some special item either ... Its just a common ol garden variety thermostat that fits a variety of vehicles and comes in a bunch of temp ranges .... brand quality is probably the most important issue ...
Ive tried 180' thermostats ... made
very little difference to fuel use ... but OBDII goes closed loop at 65' and the factory service manual mentions 160' is a satisfactory warmed up temp anyway ..... and the temps still spiked under load due to the inefficiency of the cooling system size ...
Longer warm up times are not usually an issue ... unless your climate is the cause, with ambient temps regularly under about 65'.
Take note of joe_peters "Spring thru Fall" comments as an example.
If anyone wants to play with thermostat temps to see if they get a
stable improvement ... I would suggest trying some of the ones from 182' up to 192' ... along with an efficient radiator and fan.
As for that article ...
160' & 180' thermostats being recommended ???? ... by some mob that did a cooling system upgrade ... and left the dinky little light duty,
original, fan clutch in there ???
I would be reading a few more articles as comparisons I think ....
