Temp up & down..

[~Rob~]

Shes back on the road after the new rad and FMIC. when filling up the rad on the drive, the temp was stable, however now on the road, the temp will creep up to about 3/4 up the gauge and then drop back down to normal temp, then back up again, and back down. it will keep doing this while driving, but not as frequently when just idling, and not at all with the bonnet up!
ive tried letting more air out of the system, however cant seem to get any more out! does this just sound like air still in there, or could it be a sticking thermostat?
also, what are peoples thoughts on totally removing the 'stat, and leaving it out?

[Martin F]

It sounds like you still have air in the system. Did you have the heater on full hot and the front of the car raised when you were filling and bleeding the system?

Removing the thermostat is not a good idea (you did fit it with the jiggle valve in the right direction?) as your car will struggle to come up to temperature and whilst there is a lot to be said for keeping various parts of the engine cool, they can be too cool.

[~Rob~]

Did you have the heater on full hot and the front of the car raised when you were filling and bleeding the system?

yep, thats how i did it..

you did fit it with the jiggle valve in the right direction?

i didnt remove the stat when i did the coolant and rad so it shouldnt be any different from before..

so assuming its air..do i just keep trying to bleed it out?

what the best way, undo the cap and run the engine or carefully undoing the cap once hot. ive been doing the latter.

[UltraFlynn]

You've got to find a steep hill to do it on havn't you? (Or jack the front of the car high up)

[Martin F]

i didnt remove the stat when i did the coolant and rad so it shouldnt be any different from before..


Ahh sorry I thought I recalled you saying you were going to fit a TRD thermostat.

I suspect you may well have done the following, but just to re-iterate.

Jack front of car up as high as poss.

Remove rad cap and top up rad.

Start car and turn heater on to full hot.

Bring car up to temperature and keep topping up rad as required.

Rev engine a few times to approx 3.5k to allow water pump to increase pressure.

Top rad up to the brim.

Switch off and re-fit rad-cap and top up expansion bottle.

Its worth noting that all hoses should be hot by the time the temperature needle is up to normal, if they're not then that's where you have air. Try squeezing the cooler hose.

The only time i had the same symptoms as you was when i'd filled my car in a hurry and had air in it as well. Naturally the system will bleed itself over time but if you are seeing your temperature needle moving like that you still have a fair bit of air in there and need to try and remove it.

[~Rob~]

....Remove rad cap and top up rad.

Start car and turn heater on to full hot.

Bring car up to temperature and keep topping up rad as required.

Rev engine a few times to approx 3.5k to allow water pump to increase pressure.



would this procedure be done with the rad cap back on? or would the cap be left off to allow the air to just bubble out? i did it with the cap on then undid the cap later to let the air out.

i didnt rev the car up, just let it idle.

it seems to be the return / top hose to the rad that stays cool, but i figured thats just how the thermostat works..? but then it gets noticably HOT after a while..

[Martin F]

There's your problem, you need to do it with the rad cap off ;)

[~Rob~]

Aaahhh ha! thanks!

:)