Boiling coolant

[Klasman]

Hey

Im having some problems with my coolant boiling when i turn off my car. I usually dont turn it off instantly to let it cool down abit even thou i can hear it bubbling under the hood.

Coolant is at the correct level and when i filled it last time i did it slow not to get any air pockets.

The cap is also a new uprated one so shouldn't be that either.

According to temp guage in cabin its at perfect work temp when i turn it off. But seem to rise fast when turned off.

I've also checked with EvoScan and it sais idle approx 97c and fan go on at 99c seems a bit high but im guessing the coolant shouldn't boil anyway if its mixed correctly.

Anyone got any ideas?

[Atik]

I dont want to scare you unnecessarily, but I recently had a head gasket problem which caused water to bubble into the expansion tank. BUT I was also very rapidly losing coolant in the radiator, while the expansion tank was at good level.

Might be worth doing some check just to be on the safe side, to see that you dont have the same problem I had.

Apart from that, sorry, my knowledge is very limited.

[jiggy007]

I had boiling coolant due to radiator fans not working/spinning , i just had a new sensor made........and the problem is gone....check to see if ur electronic sensor is buggered.
..i only just replace my cracked radiator, i think it cracked because of the sensor not working..hence it getting to soooo hot the rad cracked..replace the radiator, still had boiling problems...finally werked out it was the sensor...check it...
its nice to hear those fans spinning again..

[Klasman]

Im not loosing any coolant in cooler or expansion tank so hopefully not the head gasket.

The fans are working but it seems they go off to late, just checked a EvoScan log from last year and i idled at 89-90c then.

Is it hard to get that sensor out? Situated near the thermostat im guessing? (Anyone with ASA that could confirm MD177572?)

/Fredrik

[Davezj]

pm me you chassis number and i will check for you.

[Klasman]

Im going to my dealer tomorrow for a new sensor but i did some logging today and noticed that when im driving coolant is at 93C thats fine i guees but then again when driving (this was motorway driving) it doesnt need the fans.

But when i stop the fans go on to cool the radiator but only at low speed im gueesing they are 2 speed ones? When i use Evoscan to force the fans to run they spin alot faster atleast. And also they stop running at 95c if.

Should be sensor or am i wrong?

I have some EvoScan logs if anyone would like to take a look if they see anything weird.

Im not loosing any coolant and i have tried to bleed it several times just in case there is some air in there.

[Turbo_Steve]

Have to confess it does sound like there is air in there somewhere, especially if it isn't using/losing coolant....does it boil over into the expansion tank? If not, you may simply need to remove and check your rad-cap is working properly.

[Klasman]

Ive changed my rad cap recently to an uprated HKS 1,1bar one.

It does fill the expansion tank some when it gets warm.

Is there anywhere else then on the top of thermostat housing where i can bleed air?

The instrument in the dash is reading normal work temp aswell shouldnt it show overheat when its at 100c?

[Turbo_Steve]

Not if there is cavitation - the water the sensor is measuring may not be moving around enough to get hot. If you have a blockage / airlock somewhere then you will be getting parts of the system very hot whilst other stay cool.

[Nick Mann]

100 degrees is not too hot for automotive cooling applications - running at elevated pressure increases the boiling point of the water. Your system is running at 1.1 bar in addition to atmospheric pressure, which is 1 bar itself. at 2.1 bar water boils at 133 degrees, not 100. If your water is boiling at 100 degrees, then you don't have that pressure. This could be the radiator cap or some other leak that is preventing pressure from building as your water temperature rises.

Notice I said IF your water is boiling.... It still could be a trapped air issue, or a headgasket or lack of proper circulation or something else making it look like the water is boiling.

[Wodjno]

If you have recently changed your rad cap, and this has only just ecently started happening ? Then i would change it back to the old cap(If it was working well with it before?) If not get another known good rad cap and see if it still happens..

[Beastlee]

Mine does the same thing intermittently now, once every couple of months. It used to do it every time and I also had issues with pipes splitting and leaking too but I changed the rad-cap and not had a leak since.
As mentioned above I would look at the rad cap first.

[Klasman]

I replaced the cap because the other one wouldn't suck in water just press it out and changing the cap solved that problem but gave me another it seems.

Edit:
Drained and filled the cooling system today using this method.

Originally Posted by Kieran

With engine cold:

1 Drain Rad.
2. Fill with fresh water and a flush additive if you wish to use one.
3. Leave rad cap off and start car. Allow to fully warm up.
4. Put on some well insulated gloves.
5. when the thermostat opens and the coolant in the engine reaches the radiator, it'll turn the clear water to the colour of the anti-freeze. At this point, open the radiator drain valve and standby with a hosepipe.
6. As the radiator drains, gently fill with the hosepipe from the top.
7. The 'suck' side of the water pump is from the bottom hose, so provided you don't let the rad completely drain, you won't introduce an airlock. And also, pouring the hose water into the circulating coolant in the rad means that it mixes with the warm water/coolant going around the engine and so mitigates the risk of thermal shock cracking the block.

8. You basically keep going untill the draining water is perfectly clear. And this is the downside.... To flush out, then clearout the flushing agent, and then top up with coolant at the correct mix took me about 2 and a half hours and about 30 odd litres (counted using my drain bucket). But it seems effective.

So i have now bleed it and there is no air took ages, or i shouldnt say that but i dont think there is any air in there.
Well anyway i still get the same reading from EvoScan fans go on at like 99c also measured the water going out of top hose using hand-held temp reader and it read 97c and no fans on.

When are the fans supposed to go on?

[Klasman]

Just bumping to say that iv fixed it.

I replaced the thermostat and the sensor for ECU im guessing it was the thermostat.

Now idling at 90ish managed to get it to 97 with some inspired driving but never got over that.

Im guessing that's fine at least it doesn't boil ^^

Btw removing the thermostat is a PITA i managed to get the cap of when i loosened the air duct to front turbo, then jiggle a 12 spanner onto the bolt.

[Turbo_Steve]

Glad it's sorted, dude, and thank you for posting up the solution. Most likely cause looks like a sticking thermostat, then?

[Klasman]

Im gueesing so ye

[eiril_77]

can i remove thermostat (not using)

[Klasman]

If you are talking about driving around without a thermostat then i wouldn't recommend it.

It would take alot more time for the engine to reach work temperature or maybe it never does someone correct me on that one.

[crazydriver81]

Thread from the dead - But worth posting.

Had an exact same issue with my car. I had bubbles in the expansion tank, without loosing any coolant at all. A quick check with evoscan showed 97C coolant temp on idle without rad fans starting. At any time the gauge in cabin was sitting normal.

We changed thermostat, bubbling still there, coolant still at 97C on idle.

We changed the coolant temp sensor for ECU as well then and bubbling was gone. Coolant temp now is at 90C on idle with fans starting as expected. The coolant temp sensor was the fault here.

Reason for bubbling was, that the ECU coolant temp Sensor was not working properly, so there was no signal to the fans to start moving with the correct rpm. This led to high temp of coolant and let it boil when reaching the unpressured expansion tank.

Worth to check the temp reading with Evoscan, when you experience bubbles in expansion tank.

[adaxo]

Thread from the dead - But worth posting.

Had an exact same issue with my car. I had bubbles in the expansion tank, without loosing any coolant at all. A quick check with evoscan showed 97C coolant temp on idle without rad fans starting. At any time the gauge in cabin was sitting normal.

We changed thermostat, bubbling still there, coolant still at 97C on idle.

We changed the coolant temp sensor for ECU as well then and bubbling was gone. Coolant temp now is at 90C on idle with fans starting as expected. The coolant temp sensor was the fault here.

Reason for bubbling was, that the ECU coolant temp Sensor was not working properly, so there was no signal to the fans to start moving with the correct rpm. This led to high temp of coolant and let it boil when reaching the unpressured expansion tank.

Worth to check the temp reading with Evoscan, when you experience bubbles in expansion tank.

Good job Stefan, this is the issue that may Davezj experience with his bubbling coolant.

[Davezj]

Cheers Adam I will check mine, and change it if evoscan says I have lower temp than my other coolant temp gauge.

Good find.

[Davezj]

i have logged my coolant temp with evoscan and there are 2 coolant temps you can log, i have a 1998 PFL the significance of this will become apparnt as you read on,

coolant temp = Temp (raw data no formula)
coolant temp scaled =Temp - 9Deg C (formula applied X-40)

this is what eveoscan says about the two temp logs

coolant temp

For 1998+ Mitsubishi, use Coolant Temp Scaled.
Temperature of the radiator coolant water. Expect to see around 85degC - 95degC from a warmed up engine. Don't work the engine too hard until the temperature is at least 80 degrees. During racetrack use you will regularly see up to 110-115DegC. If the coolant temp goes this high, ensure you leave the key on, but not running, for 5 minutes after you have stopped to keep the fan flowing over the radiator and engine block. Anything over 120degC is going to be of a major concern, and can indicate a radiator water leak, a water pump leak, or a blown headgasket.


coolant temp scaled

This value is great for 1998 to 2007 Mitsubishi vehicles. For pre1997 mitsi use Coolant Temp.
Temperature of the radiator coolant water. Expect to see around 85degC - 95degC from a warmed up engine. Don't work the engine too hard until the temperature is at least 80 degrees. During racetrack use you will regularly see up to 110-115DegC. If the coolant temp goes this high, ensure you leave the key on, but not running, for 5 minutes after you have stopped to keep the fan flowing over the radiator and engine block. Anything over 120degC is going to be of a major concern, and can indicate a radiator water leak, a water pump leak, or a blown headgasket.
which is the actual temp value, if it is coolant temp


in normal driving i get the following
coolant temp = 100deg C
coolant temp scaled = 91-92Deg C

i have a extral coolant temp sensor and gauge set up on my car and thet reads 98-99Deg C so i am more inclined to side with the coolant temp value rather than the scaled one, which maens my engine is running to hot.
this also suggests my temp sensor is working correctly.

so does anyone know what temp the radiators fans are supposed to cut in and out?

my radiator fans never come on as fast as the air con system switches the fans on at, only slow running fans when cooling systems switches them on.
i can change the hedgehog fan controller metal box but i want to know what the fans should be doing so i can check my system properly.

[crazydriver81]

Dave, exactly the issue I had. The radiator fans do not kick in like they do, if you switch on the Aircon? The fans hardly move if the car is warmed up and idling? Temp. reading with Evoscan once warmed up and idling at approx 97°C?

Time to change the temp switch for the ECU which sits on top of the thermostat housing (with the 2 pin connector - here (http://www.camskill.co.uk/m22b0s1394p7177/MITSUBISHI_LEGNUM_GALANT_VR4_%28EC5W_EC5A%29_-_SERVICING_PARTS_TUNING_SPARES_and_SERVICE_ACCESSO RIES_-_Engine_Coolant_Temperature_Sender_-_Legnum_VR4_EC5W_and_Galant_VR4_EC5A)). This is the gremlin here.

This switch send a signal to the ECU to switch the fans on and off. The hedgehog thing regulates the rpm's of the fans but the initial signal comes from that thermostat housing sensor. After we had changed this sensor, the coolant temp on idle was at 90°C and the fans kicked in like expected. And...the bubbling issue in expension tank was gone :)

Strangely, the sensor has the correct reading, but it seems to alter the electrical signal to the fans...

[Davezj]

that interesting, as i had assumed the 2 pin sensor on the thermostat housing was just a different type temp sensor and the signal from that was feed into the ECU, the ECU did a comparison on that signal and if it was obove or below a set point in the ecu the ECU would switch the fans on or off.
i had also assumed that the temp that you could monitor in evoscan was the signal from that 2 pin sensor.
so if you monitored this temp signal and it said it 100deg C then that is what the ecu is telling you the 2 pin sensor it is monitoring is outputting. if that makes sense.

this is where i can't understand why the fans aren't working correctly. as all the things need to make the fans switch on and off seem to be in place and operating correctly.
i must have made some wrong assumption as to how the system works.

[Davezj]

i also believe it is not just the 2 pin temp sensor on the thermostat housing that makes the fans come on it is a few sensors like barometric pressue, and others.
maybe i have issues with some other sensor.

[Davezj]

i thought i had already linked to the other thread where you mention about the temp sensor.

oh that was the other thread
http://www.clubvr4.com/forum/showthread.php?67506-Radiator-fans-what-is-the-correct-operation&highlight=hedgehog

[crazydriver81]

Dave, I am not an expert on this topic. I just can tell you, how it was on my car. I think it's worth to test as this sensor is costing just a few bucks at Camskill.

My mate, a Mitsi mechanic told me, this sensor has two functions. One thing is to read the temperature, other thing is to put out a pulsed signal towards the hedgehog thingy near the fans. Additionally, the vehicle speed sensor and outside temp sensor is influencing the speed of the fans.

If you have a look at the workshop manual in category 14-12 you can find the control procedure for the hedgehog thingy and you can find the alternating voltages, representing the pulsed signal. I'm just struggling to find, where the sensor is mentioned...


As said, we were thinking that the hedgehog thing and or thermostat were faulty but then I found this thread and just tested and changed this sensor. All is fine now so it's close to think that this sensor was faulty...

[Davezj]

unfortunately i believe section 14-12 is the A/C fan operation not the coolant fan operation. i looked at that section and tested the fan controller for the A/C and it was OK.
the coolant fan operation is controlled by the 2 wires soldered to opposite side of the fan controller and they are hard wired to the fan motor. so if you change the fan controller hedgehog you have to change the fan motor at least, or cut and re join the wires to the new controller.

i will give temp sensor a go as i have a spare in the shed on an existing thermostat housing which i removed for my old VR4 so i know it works.

[crazydriver81]

You can find check procedures for the Sensor in section 13A of the manual, so you can check proper operation upfront. ;)

[Davezj]

cheers for the section pointer stefan,
yes i can check the sensor resistance, that is not a problem, i am just a bit surprised that there is not anything else in the manual about the switching temperatures for the coolant fans and what speed they should run at.

i know the fans are negatively switched, there is battery voltage on both soldered terminals on the fan controllor hedgehog, then the front wire get switched to ground in various increments, and the closer it is to ground the faster the fan spins.
my hedgehog terminal only drops be 3V, so the fans only spin slowly. not the full monty fast fans like when the A/C kicks in, if i ground the front terminal on the hedgehog the fans spin at full speed. so it is the hedgehog that is not switching on the fans fully enough, but that could be the signal the fan controllor is getting from the ECU not turn it on enough.

So the temp sensor is definitly a thing i will be testing/replacing.

[crazydriver81]

cheers for the section pointer stefan,
yes i can check the sensor resistance, that is not a problem, i am just a bit surprised that there is not anything else in the manual about the switching temperatures for the coolant fans and what speed they should run at.

i know the fans are negatively switched, there is battery voltage on both soldered terminals on the fan controllor hedgehog, then the front wire get switched to ground in various increments, and the closer it is to ground the faster the fan spins.
my hedgehog terminal only drops be 3V, so the fans only spin slowly. not the full monty fast fans like when the A/C kicks in, if i ground the front terminal on the hedgehog the fans spin at full speed. so it is the hedgehog that is not switching on the fans fully enough, but that could be the signal the fan controllor is getting from the ECU not turn it on enough.

So the temp sensor is definitly a thing i will be testing/replacing.

Did you had the chance to look into that already? I am curious if you experience the same thing I experienced?

[Davezj]

not yet, i have not got round to it.