Toyspeed.org.nz Message Board

by **FXGTV** » Thu Mar 12, 2009 4:38 pm

Car in question - 1992 sw20 - 3sgte.

As i am trying to sell the mr2 im trying to sort out its main issue. Its been over heating, and I incorrectly identified it as having a BHG. After getting a 2nd and 3rd opinion we suspect its a problem with the radiator/thermostat/cooling system. I have flushed it twice, and bled all the air out of the system, but when running it for 15 mins or so the radiator fan doesnt want to kick in. I have searched the net and this forum for answers, and have learnt a little bit, but what I want is a more detailed reason why the fan isnt kicking in. My first though is faulty thermostat and or faulty radiator cap. Ill be replacing the cap regardless but I want to know if its worth replacing the thermostat as well. Also, if you guys think it is the thermostat, care to let me know how I would go about replacing it?

Thanks in advance guys and gals,

Ryan.

by **sergei** » Thu Mar 12, 2009 4:48 pm

If you disconnect thermo-switch the radiator fan should kick in full time.
If that does not do it, then you have dud fan or faulty relay or blown fuse or some other wiring problem.

by **Twolitre** » Thu Mar 12, 2009 4:48 pm

There is a water temperature sensor on the bottom of the radiator. Unplug this and the fan should come straight on, if it doesn't then chances are the relay is dead or the fan is dead.
If the thermostat was poked then it would overheat pretty quickly, how long does it take for the water temp gauge to go over halfway?
The thermostat housing is on the drivers side of the engine next to the catalytic converter.

by **FXGTV** » Thu Mar 12, 2009 5:03 pm

Thats the thing - the gauge doesn't go over half way ever, so i assumed this meant the thermostat was poked, i.e the engine doesnt know its getting hot, so it doesnt let the fan kick in/show its over heating on the gauge. So the plug is on the bottom of the radiator, under the black plastic cover?

by **sergei** » Thu Mar 12, 2009 5:14 pm

if thermostat is suspect then check radiator when car is hot, it should be hot as well. If you don't mind getting dirty and wet, you could pull the thermostat out and check it in boiling water (or try running the car without it to see if it still overheats).
Also maybe your water pump "lost" its impeller?

by **FXGTV** » Thu Mar 12, 2009 5:30 pm

Yeah, after reading up on it it sounds like ive just got to work my way through all the possibilities. Im a car nub, the thermostat is located in a housing, near the oil filter? So i have to remove the ic piping/some of the AC bits to get to it? It doesnt help that all my tools are back in Aus :lol:

I think this problem steemed from my garage letting their apprentice change the coolant when I last got it serviced. It sounds like you need to know what you're doing to avoid getting air locks. I let the car run with the r cap off to get rid of the air lock, but it still takes a long time for it to take coolant. i.e, I fill it a little, let it drain in and repeat this many times. I guess I should just bite the bullet and take it in my mechanic - but im guessing they will take a few hours to diagnose the problem. Hmmm.

by **fivebob** » Thu Mar 12, 2009 5:31 pm

FXGTV wrote:Thats the thing - the gauge doesn't go over half way ever, so i assumed this meant the thermostat was poked, i.e the engine doesnt know its getting hot, so it doesnt let the fan kick in/show its over heating on the gauge.

Both the gauge and the ECU take their readings from the output end of the cylinder head, not from the radiator, so if it was really overheating then the gauge should show it.

by **MR2SIK** » Thu Mar 12, 2009 5:44 pm

my temp gauge has started reading lower, I knocked the plugin the engine bay and broke the plastic surround, link display still reads normally though (does link read temps from somewhere else?)

if fan relay is triggered by factory ecu, then it not reading high enough could be a reason to check out?

by **FXGTV** » Thu Mar 12, 2009 5:47 pm

ok, well then maybe there is a slight head gasket problem if thats the case. There was steam pissing out of the overflow bottle hose after i flushed it/replaced the coolant the first time around, after running the engine for about 30 mins and revving over 3 grand for a total of 5 minutes over that 30 minute period.

by **fivebob** » Thu Mar 12, 2009 6:24 pm

MR2SIK wrote:if fan relay is triggered by factory ecu, then it not reading high enough could be a reason to check out?

Radiator fan in completely independent of the ECU.

by **fivebob** » Thu Mar 12, 2009 6:32 pm

FXGTV wrote:ok, well then maybe there is a slight head gasket problem if thats the case. There was steam pissing out of the overflow bottle hose after i flushed it/replaced the coolant the first time around, after running the engine for about 30 mins and revving over 3 grand for a total of 5 minutes over that 30 minute period.

What procedure did you use to flush the coolant and refill the radiator?

If you suspect a head gasket failure then get it tested with TK Head Check liquid.

by **FXGTV** » Thu Mar 12, 2009 7:02 pm

Reading up on it I used to wrong procedure

I'm going to re-do it using all the drain plugs, as explained on the site below. I knew about the one on top of the radiator, but not the one on the heater core/the two under the car itself. http://www.toyotaownersclub.com/forums/lofiversion/index.php/t5848.html

this site is pretty damn good too. I know its a common knowledge type thing, but it would be good to have this somewhere on Toyspeed where other nubs like myself can find it :twisted:

http://www.lovehorsepower.com/MR2_Docs/mr2_bleeding_cooling_system.htm

These sites also explain the bubbling sound I could hear after running the car and turning it off. Air pockets ftl.

no grip · by **Akane** » Fri Mar 13, 2009 1:20 am

I had a fried Fan relay / control module (The black box thing) before, car wouldn't turn off properly and does all sorts of crazy shit with the fan.

by **Adamal** » Fri Mar 13, 2009 1:49 am

I hope you've bled it properly. You just about need a degree in quantum physics to do the damn thing.

by **RomanV** » Fri Mar 13, 2009 2:02 am

If you want to see if your radiator fans work, turn on the aircon.

They should both come on when you do.

by **FXGTV** » Fri Mar 13, 2009 11:59 am

Thanks guys

Yeah its a bloody complicated process! Damn mr2s!

by **Alex B** » Fri Mar 13, 2009 2:46 pm

Cant say I found it all that hard to do. Jacked up the back, filled it, opened both blead valves. Repeat until you get no air out.

by **RomanV** » Fri Mar 13, 2009 4:13 pm

Yeah it just takes ages.

by **FXGTV** » Thu Mar 19, 2009 2:36 pm

Bit of an update. What symptoms i can see now - after driving for as little as 10 minutes the coolant/water becomes very hot, and tries to push itself out. When i take off the overflow cap and get the hose out coolant continues to flow out followed by steam. It bubbles alot, and is obviously very hot. This is all while the temp gauge is reading just under half way. What would these symptoms point to? My gut says a problem with the head gasket, as a gap in it will mean water forces itself out of the radiator. Any help is appreciated as usual.

Thanks,

Ryan.

by **FXGTV** » Thu Mar 19, 2009 3:06 pm

The radiator fans come on when I switch on the AC - so i think I was worried about nothing there. Maybe I need to get a pro to bleed it - but after what ive heard it seems like alot of mechanics wont touch mr2 cooling systems with a ten foot pole. Does anyone know of any mechanics that know their mr2s in Wellington?

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Over heating Mr2 - coolant being pushed into overflow

Over heating Mr2 - coolant being pushed into overflow

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