Just posted this on a few sites, lots of help so far from Pete GP Fisher, John JSR and Dan Webster…but just wondering if anyone’s seen similar and what it may have been…
I’m fairly sure on start up prior to changing expansion tank I saw a high initial reading drop to normal but I’m now a little hazy on this point. From cold the temp rockets to 90, panicking I’ve messed around bleeding it with help from a good bunch of community folk after likely inducing more air but now I’m very sure I have no air left to bleed but the temp still rockets to 90 initially from cold before dropping to normal, pipes all hot including heater, rad hot. Temp climbs normally to 92 fan on (that’s what it’s set at), 88 fan off. If I leave it 3 maybe 4 hours then switch on the ignition the temp reads 82 and will slowly climb to 90 odd the slowly drop back to 80 without even starting the engine!
Any ideas, anybody experienced this before on a Toyota 2zz, still air in the system maybe or faulty sensor…I’m leaning towards the sensor now.
Jonnym, have you set the fan to come on at 92 or is that the factory standard? On my way home a trackday at bedford a couple of weeks ago I ended up stuck in a jam and the temp was fluctuating between 95 and 99 (when I think the fan was coming on). It sorted itself out once I started moving again though.
you should not need to drain to change the sensor, release any pressure from the system (undo cap) refit cap to give you a sealed system again. Remove temperature sender, a little bit of coolant will come out, but as no air can really get in (sealed system) not much can come out, replace sender and top up with fluid as required when hot.
As for reuse, when I drained my system to change the rad it all went into clean containers and I put it back in 2 weeks later after proalloy did their magic converting it to triple pass