Cooling Problem on 1999 Lanos - Sensor/ECU??

[ChrisHarding]

Hi All

Hopefully someone here can give me a few pointers to fix my problem!! My Lanos has done 165,000 kms and has had regular services (the aircon died so my local guys have removed the belt and pulley) BUT there seems to be a problem with the cooling. The temp gauge never rises to any more than about halfway but the motor gets pretty hot!! On very hot days in traffic once I have stopped I can hear the coolant bubbling in the surge tank and it then comes out thru the release valve in the cap so I lose coolant that way!! I have never heard the radiator fan kick in (if it does it has been on slow speed only) However if I turn the aircon switch on the secondary fan comes in and the main fan runs at slow speed and that keeps the motor a bit cooler and drops the temp a little.

Am I right in thinking that maybe the temp sensor might be faulty so it's telling the ECU that the engine doesn't need to have the fan on high speed ???? The manual says it you disconnect C2 on the ECU and then bridge C13 to ground it will test the main fan low speed and taking C12 and C13 to ground will run the fan at high speed. I CANNOT LOCATE the ECU....where is it????? in the engine compartment or cabin?????

If doing the ECU test surely the fault should be most likely the sensor that is sending low signals???? All relays for the fans look OK and both fuses seem fine too!!! The fact that with the aircon switch on, runs the main fan at low speed means the main fan isn't dead either.

I would really appreciate any help on this

Chris

Chris

[Daniel]

There is one temperature sensor (one wire) for the temperature indicator and a second sensor (two wires) for the ECU. So if your indicator is in the middle temp sould be OK. But you can measure them with a multimetre and their resistance values should be roughtly similar.

If you hear/see air bubbles in surge tank and at this moment the radiator hoses are very hard to pinch I would investigate for a blown head gasket.

Is your coolant level right? Do you need to add some?

[RichieOzzie]

Assuming the engine is the 1.5 litre.

The sensor at the top of the engine on the left hand side, just behind the vave/rocker cover is the one that sends the signal to the gauge in the car dash only. This sounds to be ok if it reads good at 1/2 way.

The second is the one underneath the coil pack on the right hand side of the engine. The Coil pack is the one with four thick wires going to it. Just under there, is the CTS, or coolant temp sensor for the electronics of the engine. This is the one the engine uses to work out if the engine is cold or hot, or somewhere in between. It is the sensor used by the ECU to work out when the cooling fans come on.
The ECU is inside the car. In the inside, on the Right looking toward the front, in the foot-well. The ECU is in the area just under the dash, and in front of the door under a cover which is commonly called the kick-panel. It is clipped in there, so easy to get out to examine.

To be honest, the problem does not sound electronic based to me either. Check when the car is warm to see if the top hose feels pressurised. (the one going to the top of the radiator). Sounds like the pressure cap could be un-well to me if pressure is low. The pressure in the cooling system stops the coolant boiling by keeping it under pressure. If you can squeeze the top hose flat at engine normal temp, then it pushes coolant out of the top of the tank, then check the pressure cap.

I am assuming no coolant comes out from anywhere else too.

The system sounds as if it is not pressurised to me, this will make this happen given the info you have said. Pressure cap first, and for what they cost, its probably worth while doing.

BTW, its a lot easier than messing around with the ECU wires, as you can potentially damage it with one wrong move.

[ChrisHarding]

Thanks Guys!!!
Yep it's the SOHC 1500 motor. The very first thing I actually did was replace the cap with a brand new one. When I bought the car about 8 months ago the owner just had water in the cooling system (mainly rusty coloured water and lots of foam!!) I flushed and replaced with coolant. Since cap replacement it has never physically bubbled again but still loses a bit of coolant on a hot day (we have had 54 days over 30 degrees this year) I have looked very carefully and the only coolant "stains" (from leaking coolant) is below the surge tank. The oil level is 100% so there's no coolant getting into there.

It's just that the motor smells pretty hot although the gauge says it normal and I have never heard or seen the main fan come in at the fast speed!!! Hmmmm I wonder if it is a head gasket??? If the head gasket has blown across from maybe a cylinder to somewhere other than the water jacket (cos there is no coolant in the oil) I changed plugs last month and the old ones looked fairly normal too!!! Any other tell tale hints that there might be a head gasket issue?????

Admittedly the car has never stopped in clouds of steam so it hasn't phyically done an overheat on me!!! It just appears and smells like it's running hotter than it should ??? The only thing I need to do is add maybe -500 ml coolant about every 200kms and drive with the aircon switch on which definately helps a bit.

Sorry last question : On other cars if you are flying down the freeway at night you normally see the temp gauge drop a bit as the cold wind keeps the motor a lot cooler...the Lanos temp guage once up to just below half way stays there and never moves whether it's a 42 degree morning or a 16 degree night drive!!! Do others notice the temp gauge drop at night on the open road??? Mine only climbs to it's mid point when you first drive off and then stays there!!

Thanks for all the help

Chris

[RichieOzzie]

Ok, so that rules that one out.

Do you sense pressure in the top coolant hose when you squeeze it?

Water in cooling system alone is a bad thing. It will allow the head/cylinder area to corrode away. The coolant inhibits that.

Sounds like it is running at normal temp according to gauge. It should just stick at where you say it goes, hot or cold day.

Need to check the top hose for pressure.

Another problem where they can leak coolant from is the warm feed to the throttle body. 2 hoses, one goes straight to the coolant tank from it, and the other feeds in. These can geta little smeggy. I usually clean the pipe on the Throttle body over with some emerycloth to smooth it all off, wipe a small amount of silicone sealant around them both, then trim the last 1-2cm off the hoses at the T.B end, and push them back on and clamp them. The trim off at the end is good to get good hose back over the pipe ends, and gets shut of the aged/crappy ends.

Make sure you don't over fill the header tank. The best way is to fill it no more than the welded seam on the tank when engine is cool. It will spit any excess out if you do over-fill it. Go back and check the next morning to make sure it sits just a fraction under the seam when cold.

[ChrisHarding]

Hey Richie

Many thanks...I'm at home today but I will be out tomorrow so I'll check the rad hose for pressure and also check the TB hoses for leaks. Is the main fan a pretty quiet one, even at fast speed??? I have never heard it come in at all. Admittedly, I have run this car for close on 10,000 kms now with no issues except the coolant and ignition leads that fell to bits when I had to change plugs!!

Thanks yes, I fill to the seam usually and after a day it's probably an inch or so lower...the coolant only made boiling sounds once so I drained and flushed and grabbed a brand new tank cap and since then it's never done it.

I'll report back after I get the motor to normal temp tomorrow

Thanks again

Chris

[ChrisHarding]

Hi Richie
OK the plot thickens so maybe this might help.
The TB hose is secure both ends (had a chance to run the car to get it up to temperature) There is plenty of pressure in the top and bottom hoses hoses too.
HOWEVER..I left it idling in the driveway with the bonnet up hoping the main fan would try to kick in when I saw steam coming from the main fan housing... I ran my hand over the radiator core and the bottom half of the core was really wet to the touch...and cold too!!! Surely that isn't normal??? It's wettest on the right hand side (if you are facing the car) and you can actually wipe away the water with your hand...it's so fine that it's hard to identify whether it's coolant or condensation but the side tanks are really hot to the touch and the bottom half of the rad core is quite cold!!! Could I have a hole in the radiator core maybe or is it normal for a core to be wet and cold at the normal running temperature. I waited a good ten minutes and the fan never came in but the core seemed to get wetter!!! The top and bottom hoses still be well pressurised and still pretty hot as were the raditor side tanks. Temp gauge after 10 minutes of sitting on the driveway stayed below halfway and the main fan never kicked in either...I was thinking that if the fan actually has a sensor in that area, it would give a false reading as the wet core is probably keeping it cool???

What do you think???? Replace the radiator ???

Thanks for your expertise

Chris

[MMamdouh]

i have some info to share with regards to daewoo cooling system

1- no matter how the engine "seems" to be hot, your temp gauge is your guide... for some reason those engines produce so much heat in the engine bay that most people would think it is over heating while it is operating normally

2- to test the fan operational status just unplug the coolant sensor plug... this will cause both fans to run at high speed... any thing else other than that means you got an issue with your fans or their relays or wiring

3- cooling fans work together and at the same speed (both low or both high)... they both kick at low speed at some 92C (or if you turn the A/C on) and they both kick in at high speed at about 98C

4- cooling fans in a lanos have 3 operating relays... one for supplying power and the other two to change how power is supplied to fans... when the fans are put in series they both run at low speed... when put in parallel they run hat high speed

5- common leakage areas on the 1.5 SOHC lanos are the coolant cap valves, hot side radiator reservoir, thermostat housing... in some cases the coolant reservoir might develop cracks at the bottom or at the mid band where the top and bottom of the reservoir are welded

for your issue... it is evident that you have a problematic radiator... seems to need welding and cleanup... i recon a new one will save you time and effort

MMamdouh

[ChrisHarding]

Thanks MMamdouh

I think that a new rad is probably easier than trying to get an old one repaired!! I'd like to test the fans...just to be sure that they do run OK as well. Richie says the sensor is under the coil pack on the RH of the engine. I'll have to check which plug to pull first.

Richie??? you agree that the radiator has seen better days?????

Chris

[MMamdouh]

their are no plugs under the coil pack but the sensor's plug... you can't miss it

MMamdouh

[RichieOzzie]

Sounds like you found the problem to me. Sometimes you have to "sweat" the problem out, so it shows itself clearly.

Radiator is leaking, and there is no way around it. It would explain the symptoms you describe, and like MMamdouh says, the only thing you can trust is the temp gauge, as it is a straight wired item..... given that the coolant is getting that far up in the engine.
I trust the gauge, and still the engine often appears to be running hotter than it should, but modern engines run, or seem to run hotter than they used to.

Another one could have been the water-pump seals leaking, which these do.


I would just change the Radiator out to be honest, unless cost or logistics are a problem.

So easy to change too.

Two top support brackets with 10mm bolts to top, wide plies to remove both clamps on hoses, and lift it upward, take off the connectors for the fans, and out it comes. Simple reversal of the process will put her back in place.

The fans are quiet ones, and sometimes they make me think twice!!

Coolant wise, the system is "Self-bleeding", so should not be too much of a problem, just when done, check over next morning.

Best to keep the coolant off the floor, and collect as much as possible.... you can even re-use it, as it is probably new anyway, just strain it through sometthing like a clean rag into a container, ready to put back in.



If this problem happened after they changed the A/C compressor, then it is likely they twisted the rad to get access to the engine area.... and in the rush, cracked/fractured the core of it. But.....

... Got to deal with the issue here, and I would save the heart-ache, fix it, and forget it.

Just a quick question though... does the A/C work correctly, as in about 20 degrees at the dash vent?

[ChrisHarding]

Thanks so much Richie

I checked this morning too and the rad is definately gone and a new one is ordered ...funny they want more for a reconditioned one than a new one!!! Nope my aircon does not work...didn't work when I bought the car and the quote to repair was more than I paid for the car so I live without it..the AC belt and idler pulley was left off so if I need to change an alternator belt it's so much easier!!!

Believe it or not I STILL cannot locate the coil pack!!! where the coolant sensor plug is!!! Are we talking about the ignition module on the right ride of the motor or am I looking in the wrong place..Is the coil pack on the motor or on the bulkhead ... I see the ignition module on the motor has a 4 wire plug going in but that is surely for the module...I'd like to double check the fans are running correctly.

Duhh!!! I'm blind!! FOUND IT!! Didn't read the post..it's UNDER the coil pack and goes directly into the end of the cylinder head!! I'll test it later when I'm back!!

Many thanks again for all the help

Chris

[RichieOzzie]

...

[RichieOzzie]

BTW, I got to ask this, and I guess others too... What's up with the Air Con?

[ChrisHarding]

Hi Richie
According to the aircon guy it leaked gas all over and he quoted me $1200 to replace everything...I think they replace the compressor and the works to avoid any issues. I only paid $1799 for my '99 Lanos last year so it wasn't worth paying nearly the value of the car just to fix the aircon. A gas refill here is $140 which would have been fine. They seem to work much like body repairers...don't fix the dent just replace the whole panel!!! He showed me stains over the driver's side shock absorber and said that was caused by leaking gas!! All the piping would have to be replaced plus a new compressor!!! Apart from that the car is great!!! No other issues!!!

Chris