Over Cooling

[SMITHEREEN]

So I've just finished the body off restoration of a Samurai SJ413 94 model soft top. Whilst body was off we replaced thermostat and radiator fitting an alloy rad all works great except it takes about 20 mins to reach half way up the temp gauge which is a little longer than Id like as it's burning through the fuel at 1500rpm. When the temp reaches halfway if the carb has been fully sprayed over with WD40 the engine revs will settle at 800RPM which is great however take it for a drive up the road and within 1/2 mile the engine temp is down to cold so choke kicks in which robs it of power etc.

I've tried covering half the rad to reduce cooling but doesn't really do much it still cools down whilst driving.

Plenty of hot air out of the heater unit

Anyone got any experience of this/ ideas how I can keep it running at optimum temp?

Cheers in advance

[lundigee]

This sounds like one of those brain teaser questions, and probably way out of my league because you will have a computer in there somewhere that will influence the outcome.
My thoughts are faulty thermostat.
The reason is if your heater is giving out lots of heat but your radiator is cold are you getting only a partial circulation through the system?

[Anton]

That's typical of a bad thermostat. It should be closed until the engine reaches temp, then it should open. The whole point of them is to bring the engine to temp quickly, and close again if the engine gets too cold (i.e. keep the engine at the correct temp).

I ran my SJ for a while without a thermostat and it behaved exactly the way you describe - 20 minutes (or more) to get up to temp, and it would get too cool at 50mph on A roads. Fitted a thermostat and the problems went away.

[SMITHEREEN]

Thanks guys, the thermostat is new so wasn't sure this was the problem as it will reach temp at standstill and stay halfway up the gauge which I figured meant the thermostat is good but it's just when you drive off as you say to 50mph temp drops

I've got another thermostat so will try it

[Anton]

Sounds to me as if the thermostat is stuck open, or it's opening at too low of a temperature. For example, if it opens at 30 degrees C, it'll look like it works correctly because it'll be closed when you fit it, and it'll open if you dip it in hot water.

I believe that the thermostat should open at 82 degrees C. Get a thermometer, heat some water with the new thermostat in it, and measure the temp when it opens. If it's much lower than 80, it's faulty. If it's much over 90, it's faulty. It should open somewhere around 82(ish).

I'd be interested to see what temp your current one opens at (assuming it's not stuck open). Be careful not to burn yourself when it opens, if it's faulty (sticking) it might pop open violently and splash hot water around.

https://www.youtube.com/watch?v=KTwoSgq ... JamesonDIY