help!!!....overheating!!

[khem]

HELP!!!!!.......My Sj runs fine generally, the temp is usually quarter way on the guage for my driving and it takes abt half the reservoir to tap it up every week.
The problem is, everytime i go on a certain high speed highway in which the vehicle has to climb the steepling hills, the temp runs up relatively quickly pass the half way mark.....what is causing this???
i can drive normally on the flat without problems, however after abt 5 to 10 mins on that highway the temp runs up!!!
the only modification on my sj is that i'm using a solex mikuni carb.......

[Tramp]

well you said ti yourself, the only thing different is the solex mikuni are you sure the carb isnt running lean? if it is, it burns alot hotter and would make your engine temperature increase. And again like you said its only noticeable at highway speeds because thats when its working hardest. when you fitted your carb did you have it set up? did you do it yourself? did you use a gunsens colour tune kit?

Luke

[Kirkynut]

Hi there,

How much past the half way mark does it go? Most run just over the half way mark by about a needle's width or so.

I agree you want to ensure that you are not running too lean though.

I'm not too sure that the temperature guage sender unit or the guage may be that acurate now days due to their age if you are running the original.

The other thing to consider is the thermostat. Might be worth replacing it, just in case it's not opening enough. They cost less than a tenner and are easy to replace.

When you say you are topping up your coolant regularly, have you look at why? It has to be going somewhere.

Have you checked you have not got a head gasket in it's early stages of blowing? Check for excess pressure in the radiator once the engine has cooled and oily deposits / mayonaisse in the radiator cap and similarly mayonaisse in the oil filler cap.

If you can't get this sorted yourself with the above advice if your mechanical knowledge is limited, take it to a garage that will not rip you off and that will give you honest advice without suggesting the most expensive thing they can think of on the spot and ask them for their advice. If you overheat it properly you will warp your head and blow the headgasket anyway, which will then be expensive!

Do the checks above, come back with the results on this forum for advice in the short term and go from there.

kirkynut

[khem]

thanx for thge advise guys....i did the entire carb swap by myself.....i'm pretty sure it isn't running leann, if anything it burns a bit extra fuel. i reved it without the cap and saw water rising out the radiator... does this mean the head gasket is blown??..it does not have any mayonaise looking deposites as well as the oil level remains ok.

to answer yr questions..
it moves up abt 3/4 the way up the guage...did wait for it to get hotter:D
i replaced the temp guage sender with one from a toyota starlet engine( 2E)....works fine
i top up every week...didn't think i was missing a lot of coolant.
i think the thermostat has been removed....i live in a tropical climate so we don't really use all that heating mechanisms.

i have been doin all my repairs on my Sj and i'm a trainimg under in the mechanical maintenance department of one of the larger companies here....so i think i'll be able to handle changing the head gasket if it comes to that...also i have the SJ manual

[zukimoo]

mine run about a 1/4 at slow speed and go to half on the highway. Check the fan clutch. If it's worn it will not turn at full speed and cause a lack of cooling.

[khem]

ok thanxx
quick questions
how do i check it?
does the water rising out of the radiator mean that the head gasket is blown?

[Tramp]

in fairness when the engine is hot the water expands and it does put abit of water back into the expansion tank but excessive amounts can indicate the head gasket, i ran my sj for 6-12months with the head gasket gone ( i.e. just excessivly using water) after a while i started to get the mayonase build up in the oil filler cap,

to check your fan is working, rollup a newspaper, and when the engine coolant is cold and the engine is running you should be able to stop the baldes with the paper, when the coolant is hot, repeat the test but this time you shouldn't be able to stop it,

finally put the original temp sender back in, the one you have fitted might not have the same resistance readings as a standard, different senders have different resistance readings at different temperatures so although it might be alright while the engine is cold, when it gets hot it could be giving spurious readings

Luke

[ScottieJ]

if there are bubbles coming out of the radiater when you rev it, that could be a sign of a blown head gasket, sometimes if you rev it and then have a bit of a sniff over the radiator while its bubbling you can smell exhaust gas with a blown head gasket so try that.

Scott

[Zukipilot]

Have a look under the inlet manifold. It's easier if you use a small mirror. You should see two core plugs that are made of mild steel. These rust and create pinholes where the water leaks out. Under normal conditions the rust seals the holes as the pressure is low, but as you tear down the motorway at ta top speed of 65mph, or go offroad, the pressure can increase and water is forced out without you knowing there is a leak. Check for rust stains and replace the core plugs if they are rusty.

[khem]

thanxx broo.....i changed the head gasket today and the water has stopped coming out the radiator.....i'll give it a run next weekend and see how the temp behavess......and i'll check the plugs alsoo.......FYII...i was ablee to push my sammy pastt 80 mphh and this with a blown headd gaskett....gotta lovee my new carbb:D:D...cant wait too see what i can get with the new gasket:)