Sudden Temperature Hike

Amila G · October 28, 2013

Hi guys,

I have a diesel corolla 110 manual one. This evening when returning home I stopped at a gas station and when pulling to the road I noticed that the temp gauge had suddenly moved above the 3/4 mark. It was fine (in the 1/2 mark) about 2 mins before.

I thought the needle was acting up but pulled over turned off the engine and turned the key back to ON, then the needle came to the 1/2 mark, but when started, it moved from 1/2 to 3/4 within about 20 seconds !. I drove again for few seconds and the gauge kept rising so I stopped and checked the fans. AC was off and both the fans were off although the temp was high.

When the engine is off and the key is in ON the needle sits around the half mark and it went up only when the engine is started,

Then I turned on the AC and then the temp slowly became normal. Then I started driving again but the temp kept rising when the AC cuts out. But the whole drama was over in another 10 mins and everything is back to normal now. Now the temp is normal and the fans come on usual way. After that I noticed the radiator top tank was almost empty although the plastic tank has coolant in it (but the temp was fine although the radiator was missing close to 1L of coolant). When the temp was high I noticed a bit of coolant where the top tank meets the radiator core and there was a bit of smoke coming from the tube that goes into the plastic tank from the radiator - is it normal ?

So my questions are could this be due to a bad gauge or an issue with the fans. - I mean will the temp go up that fast (1/2 to 3/4) in 20 seconds if the fans are not running ?

My trusty old electrician is gone so I'm kinda hesitant to show this to an unknown guy as the issue is gone now. Could you recommend a good place around Nugegoda area ?

Lastly any other symptoms of overheating engines if you don't / can't trust the temp guage ?

maheshw · October 28, 2013

well this is something similar to my story. it was a bad relay which connects radiator fans. it kicks on only some times after temp gauge reach 3/4. some times not. best thing to meet your electrician asap.

Rumesh88 · October 29, 2013

Agree with maheshw but in addition you may have a leak in your radiator somewhere. Since the system did not boil over there is no reason for the coolant loss while there was some coolant still left in reserve unless it was leaky.

bogzy · October 29, 2013

To be on the safe side, why not do a pressure test on the radiator and make sure there is no leak as rumesh said. There is a place just before nawinna @rp*co on the same side when going towards maharagama, pretty competent people.

Amila G · October 31, 2013

Thanks guys. I replaced the radiator cap as there was a bit of rust in the inside. Now the radiator is not loosing any water.

But the temperature increase did not happen again, so if I take the car to a mech I dont think he'll be able to find anything wrong. Or else can a good electrician can find a bad relay or something when it's not failed yet ? and can you suggest a guy near Nugegoda area.

MkX · October 31, 2013

Your symptoms most likely caused due to bad radiator cap. If there is no leaks visible on any of the hoses plastic tank can overflow. You can observe the coolant resedue near the cap of the plastic tank.

However you say that you can see bit of coolant near toptank and radiator core. That is where it seal, and I think overheat has already damaged the seal. if this is the case you will have to replace the radiator or get it repaired. But long term solution is a replacement.

However if you are lucky, the smoke and coolant you obsearved can be a result of overflowed coolant from the plastic tank due to bad radiator cap.

Amila G · October 31, 2013

Thanks MkX,

But I don't think that the overheating and the water level going down is related, The whole overheating drama lasted only about 10 - 15 mins and it went away by itself. I tried several time by revving up the engine without the ac after returning home but the fans worked fine and the temp never went up. I checked the water level (in the radiator itself) after that (when the engine was cool enough to open the cap).

Now there is no coolant near the seal however I could see a bit of coolant coming around the seal if water of poured on to the hot radiator (like when washing the car). It was there from a long time but my mech said it;s not a big deal as there was no major coolant loss at that time.

I'm not sure even if the engine actually over heated as the gauge went up so fast and it was over by itself

I guess the radiator is some sort of plastic (at least the top tank). is it possible to repair the seal properly ?

Rumesh88 · October 31, 2013

Now there is no coolant near the seal however I could see a bit of coolant coming around the seal if water of poured on to the hot radiator (like when washing the car). It was there from a long time but my mech said it;s not a big deal as there was no major coolant loss at that time.

Your mech is dead wrong. It is a big deal even if the leak is small. If you have a leak in the radiator system it is NOT just a matter of coolant loss but a major issue with the boiling point of the coolant. Why we have a sealed radiator system with a pressure cap is to maintain a higher pressure than the atmospheric pressure inside so that the coolant does not boil and form vapor bubbles. In addition as the system cools down it is supposed to suck in coolant from the reserve. But even with a hairline crack on the radiator ow it will suck in air as well. So get the system sealed first! Otherwise it is a matter of time before the same problem repeats.

Edited October 31, 2013 by Rumesh88