Overheating? cold bottom hose head over 110 celcius

[Paulinwales]

Hi All,

I have a sesnor fitted the the cylinder head and the temp has never gone above 109'C (only when driving hard on prollonged hills).Today it got up to 110 (where i set the alarm). I immediately stopped, and put heater fans on full. I checked the bottom hose which was cold,the top hose was hot. temp guage was still at 11'oclock. I waited till the temp had fallen til i drove the 1 mile home. Temp got to 105'C before i was home. I had driven for about half an hour previously.

Is this likely to be caused by a faulty thermosta? locked open/closed position?
how should i test the bongo to diagnose and best sort out this potential problem?
I suspect I stopped well before any damage was done
coolant levels were fine not that much pressure in system though. I have recently flushed, bled and added new red longlife coolant with no problems each time ensuring the bottom hose was hot as per youtube video.

your ideas please thanks in advance, Paul ( i'm not that expereinced in repair)

[stilldesperate]

The stat, afaik, is fully open at about 84deg, (this is the water temp). If the water is over this temp, and the lower rad hose is cold either:
a. The stat isn't opening (or the rad might be blocked), or
b. How sure are you of the temp readout accuracy?

If the gauge is still at 11 0'clock, has the meter been undamped, or is it standard?

If there was no excess pressure when opening the pressure cap at 105 degrees, I'd question that it was at that temp.

SD

Sure Ady / Haydn will be along to comment soon

[missfixit70]

Where on the cylinder head is the sensor?
When you stopped, did you stop but leave the engine runnning, ie water pump still pumping the coolant around to help cool the engine?
Did the Rad fans or scavenge fan cut in at all?
Had the coolant level dropped? (Do you have a low coolant alarm?)
The fitted gauge will not move until it's basically already overheating (this can be remedied by modfying the gauge or fitting a Mason alarm which modifies it & provides a settable alarm).
If the bottom hose is cold immediately after stopping (with engine still running) then the system is doing what it should, ie the rad is cooling the coolant, hot goes in the top, cold goes out the bottom. It's only when stationary or going slowly/under heavy load with little or no airflow over the rad that the bottom hose will start getting hot, ie if you pull over, leave the engine runnning & after a few minutes the bottom hose will get warm then hot, then as the the coolant temp reaches @96 degrees C at the sensor on the passy side, the low speed fans should cut in, bringing the temp down, if this is still not enough, then if it gets up to 108 degrees C (coolant temp) then the high speed fans shoulds cut in.
All of this of course is pointless if you have turned off the engine as there is no flow so no cooling will take place.

[missfixit70]

The stat, afaik, is fully open at about 84deg, (this is the water temp). If the water is over this temp, and the lower rad hose is cold either:
a. The stat isn't opening (or the rad might be blocked), or
b. How sure are you of the temp readout accuracy?

If the gauge is still at 11 0'clock, has the meter been undamped, or is it standard?

If there was no excess pressure when opening the pressure cap at 105 degrees, I'd question that it was at that temp.

SD

Sure Ady / Haydn will be along to comment soon

That's where the stat starts opening, fully open is @ 94 degreesC from memory, ie just before low speed fan switching point.
Cylinder head temp & coolant temp can be two different things, depending where the sensor is mounted.

[Paulinwales]

Where on the cylinder head is the sensor? I put a sensor into the screw thread on the top cyclinder as per overheating alarm is that the mason alarm? It's been working reliably since february

When you stopped, did you stop but leave the engine runnning,ie water pumpstill pumping the coolant around to help cool the engine? - no i turned it off, and turned the ignition to allow the fans to come on. There seemed to be a lot of fan noise. I also opened the bonnet to aid cooling.

Did the Rad fans or scavenge fan cut in at all? - no sure what these are, was alot of fan noise.

Had the coolant level dropped? (Do you have a low coolant alarm?) - just monitor the coolant regularly and have uv dyde to detect any leaks was fine. It had a leak when i first got it and fixed it so used to monitiring often.

The fitted gauge will not move until it's basically already overheating (this can be remedied by modfying the gauge or fitting a Mason alarm which modifies it & provides a settable alarm). - unmodified gauge backed up by temperature probe

If the bottom hose is cold immediately after stopping (with engine still running) then the system is doing what it should, ie the rad is cooling the coolant, hot goes in the top, cold goes out the bottom. It's only when stationary or going slowly/under heavy load with little or no airflow over the rad that the bottom hose will start getting hot, ie if you pull over, leave the engine runnning & after a few minutes the bottom hose will get warm then hot, then as the the coolant temp reaches @96 degrees C at the sensor on the passy side, the low speed fans should cut in, bringing the temp down, if this is still not enough, then if it gets up to 108 degrees C (coolant temp) then the high speed fans shoulds cut in.
All of this of course is pointless if you have turned off the engine as there is no flow so no cooling will take place.

should i run the engine and monitor bottom hose?

[missfixit70]

I don't know, if you answer the questions & give us a bit more info, it will help to see if there actually is a problem? May just be a case of bongo paranoia

[Paulinwales]

Kirsty/miss fixit, I quoted you and supplied the answers next to your questions as best i could

rgds Paul

[missfixit70]

Sorry, didn't see that
Still not sure where the temp sensor is though, drivers side or passy side, front or back?
Had the coolant level dropped in this instance - not generally in the past?
Sounds like the fans came on then, don't forget the ambient temperature is getting warmer (in theory ) as we get into the summer, so a few degrees rise from winter running is to be expected.
If there are no obvious leaks, levels are ok, I'd run it up & see what happens I think, if you've got something you can use to monitor the temp on the top hose coming out of the head under the drivers seat, that'd be good, should give you a decent indication of coolant temp.

[missfixit70]

Mason alarm is not a seperate readout, it's a small module with 3 connectors that connect into the back of the temp gauge to modify the damped down signal so the existing temp gauge reads sumat useful & provides a settable alarm, this can also be achieved with a bit of soldering/snipping & a resistor as per a mod mentioned in the coolant alarms factsheet I believe & on Haydn Callows website, probably on here somewhere too

[Paulinwales]

i put the sensor under where the arm rest lies i.e. put seats back took of the middle back plate, and put on screw on top of head there was a thread a screwed it into

rjust ran it up and down the hill and would not go past 95'c so not sure what's happening, might change battery on thermometer - it's a cooking one adaptedt o do the job - good for 200'C

bottom pipe came on after running a few minutes stationary

[haydn callow]

Which temp alarm have you got ??? you say it's not a MASON (that would make the temp gauge move about)
You say you havent a Low Coolant Alarm so that rules out the LCA?TM-2 combo.

What exactly do you have and where exactly is the bolt hole you have the sensor in...Is it under the passenger seat by the side of the alternator.....Too HOT there for the sensor (close to exaust)

[rita]

Which temp alarm have you got ??? you say it's not a MASON (that would make the temp gauge move about)
You say you havent a Low Coolant Alarm so that rules out the LCA?TM-2 combo.

What exactly do you have and where exactly is the bolt hole you have the sensor in...Is it under the passenger seat by the side of the alternator.....Too HOT there for the sensor (close to exaust)

Sounds like a cooking thermometer/probe.

Cheers..

[jaylee]

i put the sensor under where the arm rest lies i.e. put seats back took of the middle back plate, and put on screw on top of head there was a thread a screwed it into

rjust ran it up and down the hill and would not go past 95'c so not sure what's happening, might change battery on thermometer - it's a cooking one adaptedt o do the job - good for 200'C

bottom pipe came on after running a few minutes stationary

It is!!

[missfixit70]

Sounds to me like an uncalibrated temp monitor that is fairly well out giving rise to bongo paranoia then
Try calibrating the temp monitor in boiling water, ie 100 degrees c & see what it says.

[Paulinwales]

yep i's a cooking probe (short on money) was trying to avoid the embarresment of owning up to it.

i put it under the metal sheet that the arm rest goes on from a diagram showing where to put the temp alarm for one of hayden's proper alarms as a stop gap till i can afford one!. Lets hope it's that playing up I changed the battery also (it was starting to fade a bit on the screen )and i'll do a short local run tomorrow and let you good folks know

rgds Paul