overheating at low speed saga :(

[zeronine]

Hi, here's the whole scenario -

Yesterday I took my '91 na for it's first drive since having a cambelt service & MOT. I hadn't driven it for a couple months since buying it as bits were done to get it through MOT. When I bought it I drove it 30 miles to my folks without any hint of overheating - that was before winter - the last I started it was New Years eve and the cambelt jumped and thus the following cambelt service.

FF to yesterday and I wanted to bring the MR2 home. So I headed out for a 90 odd mile drive but before I departed I thought I'd topup the coolant fluid - as it was early Halfords was closed and I wasn't aware of the whole 'red coolant' thing - I just used what I had in the garage which wasn't much.

The car went smoothly with the Temp gauge horizontal. I covered about 15 miles & pulled over at a Shell services to buy some proper Coolant from them - then I noticed that the car started blowing steam out of the expansion cap as I drove slowly through the forecourt and came to a stop and parked! The Temp gauge had risen almost to the max...

I waited then topped up with the new Shell Coolant (it's in a goldish carton). I didn't follow any bleeding procedure (cos I only read about that last night!) but I did pour the coolant in slowly trying to keep air from entering the system.

Anyhow I set off again and for the rest of the motorway miles to north Kent the temp sat at mid gauge and the car was great! I had the heater on too. I didn't push it and cruised along at 65-70mph quite comfortably all the time watching the gauge & listening to to the cricket.

Then when I exited the M20 and drove the mile or so to my house the car started to overheat again and when I pulled up outside my garage as England beat SA the little '2 spewed all the new coolant out the expansion cap and over the nice clean driveway...it must have got overly excited...

So - what the heck is up with my '2 overheating at low speed?

Thanks in advance!

[dazzz]

Did you fully shut the rad cap. The rad cap is the metal cap where you top up the coolant. It has two positions, semi shut and shut.

The expansion tank is a plastic bottle that fills with coolant.

Probably needs a good burping.

[R6 RIDER]

My farther has a 92 n/a and his was overheating , your coolant pipes could possibly be blocked hence your overheating , or your leaking fluid !!! good luck in any case finding your sollution.

The members on here are very intelligent , they have already helped me save my engine ,and ive only been on here a few days lol , they are quick with there replies and im sure they can help you. Kind regards . R6 rider

[zeronine]

Did you fully shut the rad cap. The rad cap is the metal cap where you top up the coolant. It has two positions, semi shut and shut.

The expansion tank is a plastic bottle that fills with coolant.

Probably needs a good burping.

Do you think air in the system would cause the overheating like this Dazzz?

The rad filler cap (yellow top) was fully closed as far as I could tell, but it was the black one on top of the expansion tank that was popping off and blowing steam and the coolant was pouring out of the overflow pipe.

R6 - I looked under the car and in the engine bay - no signs of leaks, but I have noticed that the radiator is a little on the tired side, and quite possibly leaking on the NS bottom as there's a bit of fresh coolant there, but not a lot compared to what came out of the overflow pipe!

[R6 RIDER]

Hi there , i would switch engine on and leave untill up to temp and then check the radiator , see if it slightly leaking , if it is it will only be a very fine spray , as this was my farthers first problem. He put some radiator fluid in so it would seal this but putting in too much can block your pipes , and cause over heating , another time it over heated was when it was very cold and the fluid inside the pipes had frozen and blocked itself. Any how check your radiator properly for leaks . Kind regards. R6 rider

[JDM-MAT]

Sounds like somet I had to sort out on my supra, it just needed a new rad cap and all was well.

[JDM-MAT]

Saying that my skyline did the same thing and I could not find a fault so I dropped the fluid flushed every thing out, took all the pipes off and the expansion tank off cleaned them and filled it all back up bleeded it and it was fine.

[zeronine]

thanks JDM-MAT - did you flush the system with a water from a hose and some engine flush?

The expansion tank is pretty dirty - it could certainly do with a good clean

[JDM-MAT]

I just use a hose and blasted it through untill the water was clear that was coming out. The water in the skyline was horrid brown and stuff in it build up I guess. But yeah blast it through the radiator and engine then do all the pipes and tank on there own

[zeronine]

I've got a new rad on the way from MR2-Ben so I'll tackle it all later in the week.

[JDM-MAT]

I've got a new rad on the way from MR2-Ben so I'll tackle it all later in the week.

i guess you will flush/clean the system before you fit it?

[Fourveesix]

Possibly the rad cap.
Toyota rad caps have two functions, one is to actually seal the system from atmosphere, the other is a pressure cap inside the rad cap to vent off expanding coolant to the bottle which gets sucked back in when cold.

If the rad cap isnt leaking but its boiling up it means that the caps pressure function isnt doing what it should and its venting off too much, a symptom of which will be the expansion bottle gets overfilled and rad level gets lower each time the engines been run.
Replace it but check all the hoses for signs of weeping etc and the radiator also.

[JDM-MAT]

Possibly the rad cap.
Toyota rad caps have two functions, one is to actually seal the system from atmosphere, the other is a pressure cap inside the rad cap to vent off expanding coolant to the bottle which gets sucked back in when cold.

If the rad cap isnt leaking but its boiling up it means that the caps pressure function isnt doing what it should and its venting off too much, a symptom of which will be the expansion bottle gets overfilled and rad level gets lower each time the engines been run.
Replace it but check all the hoses for signs of weeping etc and the radiator also.

+1 as I said haha with out the tech talk

[pbmr2]

if it's only doing it after slowing down from higher speed, are you sure the rad fan is working?

my mate's 2 got too hot on a motorway due to traffic and no rad fan. turned out that there was no fuse in there!
other causes could be blown fuse or faulty temp sensor... maybe dead fan but i doubt that.

he also had a leaking pipe from hell too, but only a tiny bit. was enough to let air into the system now and again causing an airlock every couple of weeks.

good luck!

[blue2]

I replaced every coolant pipe, water pump, thermostat, coolant, you name it to solve my issue. Its usually something really simple. When the car is warm give the rubber coolant pipe a squeeze and make sure its firm. If its not then its losing pressure from somewhere so check all connections are tight.
When the car is overheating give it a good rev (up to 5k) see if the temp gauge drops back down, if it does its more than likely your water pump.
Good luck cos the coolant systems on this car are a bloody nightmare!

[zeronine]

Yeah JDM-MAT I'll flush the whole system when I pull off the old radiator. That should make it easier to flush everything out.

I've taken a look at the radiator cap (mine has a yellow) decal - it's pretty perished on the rubber seal, so on your advice Fourveesix I'll replace that too.

I'm not actually sure the rad fan is working pbmr2 - what temp should that come on at? new fan sensor...

[Fourveesix]

Possibly the rad cap.
Toyota rad caps have two functions, one is to actually seal the system from atmosphere, the other is a pressure cap inside the rad cap to vent off expanding coolant to the bottle which gets sucked back in when cold.

If the rad cap isnt leaking but its boiling up it means that the caps pressure function isnt doing what it should and its venting off too much, a symptom of which will be the expansion bottle gets overfilled and rad level gets lower each time the engines been run.
Replace it but check all the hoses for signs of weeping etc and the radiator also.

+1 as I said haha with out the tech talk

Noot wrong with a bit of tech!

[JDM-MAT]

Possibly the rad cap.
Toyota rad caps have two functions, one is to actually seal the system from atmosphere, the other is a pressure cap inside the rad cap to vent off expanding coolant to the bottle which gets sucked back in when cold.

If the rad cap isnt leaking but its boiling up it means that the caps pressure function isnt doing what it should and its venting off too much, a symptom of which will be the expansion bottle gets overfilled and rad level gets lower each time the engines been run.
Replace it but check all the hoses for signs of weeping etc and the radiator also.

+1 as I said haha with out the tech talk

Noot wrong with a bit of tech!

lol nope i just could not be ar$ed at the time

[JDM-MAT]

Yeah JDM-MAT I'll flush the whole system when I pull off the old radiator. That should make it easier to flush everything out.

I've taken a look at the radiator cap (mine has a yellow) decal - it's pretty perished on the rubber seal, so on your advice Fourveesix I'll replace that too.

I'm not actually sure the rad fan is working pbmr2 - what temp should that come on at? new fan sensor...

i think about 95c ish

[zeronine]

I ran the '2 for a bit to get it up to temp and to see if the fan came on. Nada.

I let it stand then opened the two bleed valves in the frunk and air hissed out! I did it a few times after starting the car each time and running for about 2 minutes.

{I also took off the oil cap to see if there was any oil activity while running - nada - so I topped the oil up too. On the stick it's near max now.}

The hose going to the rad cap is ultra hot but the pipes coming out of the engine at the front are cool, the one on the OS (drivers side) is warmer near the thermostat housing - but the two pipes coming into the frunk and into the radiator are ice-cold. How's that???

Which direction does the coolant circulate?