Overheating - real or imaginary ?
Discussion
Apologies for yet another 'overheating' thread, but I have read every previous thread on this subject and despite their combined information and advice I am still none the wiser......
PLEASE READ ALL OF THE INFO BELOW BEFORE OFFERING ADVICE.
According to the temp gauge, the car has always been a 'hot runner' to the point that the engine should have died 2.5 years ago, as such I have always suspected the temp sender and/or gauge were less than reliable.
But after 2.5 years I am fed up of not knowing the true temp of whats happening under the lid thing at the front and always wondering if the gauge is right for once.
Facts
1. the gauge shows 'normal' temps when on the move e.g. when making good progess 75-80 degrees.
2. when stationary / low speed stop start - the gauge can show 100-110 degrees. (PLEASE NOTE this has been 'normal' behaviour for 2 years)
a) there has NEVER been any release of coolant through the expansion tank pressure cap
b) temp steadily drops again towards 'normal temps' once on the move
c) oil pressure always 15 psi in stop start traffic and 40 psi on the move
d) coolant levels are a) 1 inch or so from TOP of swirl tank b) 1-2 inches from bottom of expansion tank (this appears to be its natural level as anything else gets expelled)
3. I have the Mod Wise 2 speed fan controller fitted, half speeds come on at 75 degrees and full speed comes on at about 85 degrees (according to the dashboard temp gauge)
4. Fans are working normally
5. A new temp sender was fitted 4 weeks ago as the previous one had corroded. The new temp sender was a TVR supplied part. HOWEVERr the housing for the temp sender had been butchered in the past and as such the new temp sender had to be Heath-Robinsoned into place.
On saturday the gauge showed 115 degrees when sitting in traffic...........
6. the cooling system was drained and re-filled 4 weeks ago
7. The radiator was re-cored 2.5 years ago
Possibilities
a) temp gauge is right and I am running VERY (terminally) hot but for some reason coolant doesn't boil at 115 degrees
b) temp gauge is wrong.........
c) temp sender is affected by poor housing and localised heat
d) air lock in coolant system that means the temp sender measures hot air rather than liquid
I want to prove which one of these is correct because a) or d) could obviously be fatal
I have tried using Gunston pocket meter wíth temp sensor to identify external temps of various components, but am not sure how much I can rely on this ?
Any advice on quickest and easiest route to determine the issue would be much appreciated (would prefer to narrow scope of it down prior to booking it in for any dashboard off and engine apart jiggery pokery).
Thanks in advance
PLEASE READ ALL OF THE INFO BELOW BEFORE OFFERING ADVICE.
According to the temp gauge, the car has always been a 'hot runner' to the point that the engine should have died 2.5 years ago, as such I have always suspected the temp sender and/or gauge were less than reliable.
But after 2.5 years I am fed up of not knowing the true temp of whats happening under the lid thing at the front and always wondering if the gauge is right for once.
Facts
1. the gauge shows 'normal' temps when on the move e.g. when making good progess 75-80 degrees.
2. when stationary / low speed stop start - the gauge can show 100-110 degrees. (PLEASE NOTE this has been 'normal' behaviour for 2 years)
a) there has NEVER been any release of coolant through the expansion tank pressure cap
b) temp steadily drops again towards 'normal temps' once on the move
c) oil pressure always 15 psi in stop start traffic and 40 psi on the move
d) coolant levels are a) 1 inch or so from TOP of swirl tank b) 1-2 inches from bottom of expansion tank (this appears to be its natural level as anything else gets expelled)
3. I have the Mod Wise 2 speed fan controller fitted, half speeds come on at 75 degrees and full speed comes on at about 85 degrees (according to the dashboard temp gauge)
4. Fans are working normally
5. A new temp sender was fitted 4 weeks ago as the previous one had corroded. The new temp sender was a TVR supplied part. HOWEVERr the housing for the temp sender had been butchered in the past and as such the new temp sender had to be Heath-Robinsoned into place.
On saturday the gauge showed 115 degrees when sitting in traffic...........
6. the cooling system was drained and re-filled 4 weeks ago
7. The radiator was re-cored 2.5 years ago
Possibilities
a) temp gauge is right and I am running VERY (terminally) hot but for some reason coolant doesn't boil at 115 degrees
b) temp gauge is wrong.........
c) temp sender is affected by poor housing and localised heat
d) air lock in coolant system that means the temp sender measures hot air rather than liquid
I want to prove which one of these is correct because a) or d) could obviously be fatal
I have tried using Gunston pocket meter wíth temp sensor to identify external temps of various components, but am not sure how much I can rely on this ?
Any advice on quickest and easiest route to determine the issue would be much appreciated (would prefer to narrow scope of it down prior to booking it in for any dashboard off and engine apart jiggery pokery).
Thanks in advance
a) temp gauge is right and I am running VERY (terminally) hot but for some reason coolant doesn't boil at 115 degrees
Not a chance... you'd have blown some hoses by now just with the expansion, plus the heat shimmer off the bonnet, stench of very hot oil, lumpy running etc etc would be telling you its too hot. You don't need a guage to tell you you're at 115 degrees, the pressure cap would be venting steam too.
b) temp gauge is wrong.........
Indeed..
c) temp sender is affected by poor housing and localised heat
Pass.
d) air lock in coolant system that means the temp sender measures hot air rather than liquid
Unlikely or you really would overheat if you had airlocks in the system.
Cheers,
Matt.
>> Edited by M@H on Monday 19th April 13:58
Not a chance... you'd have blown some hoses by now just with the expansion, plus the heat shimmer off the bonnet, stench of very hot oil, lumpy running etc etc would be telling you its too hot. You don't need a guage to tell you you're at 115 degrees, the pressure cap would be venting steam too.
b) temp gauge is wrong.........
Indeed..
c) temp sender is affected by poor housing and localised heat
Pass.
d) air lock in coolant system that means the temp sender measures hot air rather than liquid
Unlikely or you really would overheat if you had airlocks in the system.
Cheers,
Matt.
>> Edited by M@H on Monday 19th April 13:58
The whole cooling system has a complete chapter on it and is covered pretty well in the bible. Take the temp of the cooling system at various points and see if it is anywhere near that of the sensor. The sensor itself is difficult to get to but the major water pipe to the swirl tanks/rad is the best place to check. If the rest of the system is not at the temp indicated by the guage then there is a fault with it or the sensor.
BTW the gauge sensor is hidden behind the dizzy and doesn't suffer from bad positioning etc. The ECU one is in the front of the engine but has nothing to do with the temp sensor or otter switch.
BTW the gauge sensor is hidden behind the dizzy and doesn't suffer from bad positioning etc. The ECU one is in the front of the engine but has nothing to do with the temp sensor or otter switch.
The infrared ones are easier to use - point and shoot and are around £40-50. The Gunson one could be worth a try as you already have it but the accuracy depends on thermal contact with the sensor which can be tricky.
The infra red one is also great for barbecues and working out cooking time, finding out cloud height (point at cloud and you can work out the height roughly by the temp difference) and a host of other things like whether wine is at the right temperature. Indispensable.
The infra red one is also great for barbecues and working out cooking time, finding out cloud height (point at cloud and you can work out the height roughly by the temp difference) and a host of other things like whether wine is at the right temperature. Indispensable.
shpub said:
.........
BTW the gauge sensor is hidden behind the dizzy and doesn't suffer from bad positioning etc. The ECU one is in the front of the engine but has nothing to do with the temp sensor or otter switch.
Stu, which sensor/sender did you change?
Steve, is the gauge sender into a waterway in the block or the pump inlet? Haven't read up on this in the bible yet......!
the dodger said:
Stu, which sensor/sender did you change?
Rog - the original temp sender (water temp) was corroded and was swapped out for a TVR supplied one.
Pete advised that the original had been 'butchered' into place at some stage and that the housing was not perfect. He managed to get the new one to fit with some jiggery pokery, but I still get the same high readings (110-115).
a) the new temp sender is kaput ?
b) the new temp sender is the wrong part ?
b) the new temp sender is impacted by the fact that the housing has been damaged ?
c) the gauge isnt calibrated correctly ?
Q - Once I have been able to confirm that the gauge is wrong, what is recommendation for next stage ? Should I try and utilise the 'spare' sender on the top of the block ?
Q - what is involved in doing this & what equipment is needed ?
I was in doubt of my temp gauge readings a while ago, if your careful, from cold run the car up with the filler cap off, then dangle a thermometer in the coolant and check the temp on th egauge. You can do this several times before it gets very hot, then refit the cap before the red gets hit. My gauge reads a little high but had no problems doing this. You will have to wait till the thermostat opens of course to get a decent reading. it is possible to do this without injury, just need to be careful and watch th ewater level rise as it expands.
shpub said:
BTW the gauge sensor is hidden behind the dizzy and doesn't suffer from bad positioning etc. The ECU one is in the front of the engine but has nothing to do with the temp sensor or otter switch.
Stu which sender did you change?
Not accusing you of anything but i do know your mechanical background....
The spare sensor (if its there...) is not a direct replacement. It requires a padding resistor so that it will give the correct reading at the required temperature. The resistence curves are not the same and while you can get this happy ness value, the guage will not be accurate outside of this point.
Your decision and it will give you some indication but I prefer to have guages that work correctly across the range as the temp reading is very importent in giving early warnings.
If the temp reading is out, I would get a new sensor and test it out of the car before installing. The sensor could be duff, the wrong one or the guage is screwed.
The first thing to do is check that the temp is right or wrong and not worry until you have confirmed that.
>> Edited by shpub on Tuesday 20th April 10:48
Your decision and it will give you some indication but I prefer to have guages that work correctly across the range as the temp reading is very importent in giving early warnings.
If the temp reading is out, I would get a new sensor and test it out of the car before installing. The sensor could be duff, the wrong one or the guage is screwed.
The first thing to do is check that the temp is right or wrong and not worry until you have confirmed that.
>> Edited by shpub on Tuesday 20th April 10:48
Steve - agreed, I will only feel comfortable once the gauge shows the correct temp.
As an interim test prior to getting the Infrared Thermometer, I have ordered some self adhesive Temperature Indicating Labels -
"These self adhesive irreversible labels are ideal for applications requiring a permanent record of the temperature reached as each element changes colour to black and remains so, as the temperature is exceeded. Their performance is not affected by transient contact with oil, water or steam. A variety of temperature ranges is available up to a maximum of 10 levels per strip. They are accurate to ±2% of their stated reading (5 degree increments up to 116 deg C)" (7 quid for a pack of ten).
Next time I go for a drive, these will be stratgically placed on the block, inlet pipe to swirl tank, inlet pipe to rad, outlet pipe from rad etc.
Once I get back, I will be able to see the highest temp reached by each of the components & check against the highest temp shown by the gauge.
Anybody have a feel for the price to get a new sender & gauge fitted & claibrated ?
As an interim test prior to getting the Infrared Thermometer, I have ordered some self adhesive Temperature Indicating Labels -
"These self adhesive irreversible labels are ideal for applications requiring a permanent record of the temperature reached as each element changes colour to black and remains so, as the temperature is exceeded. Their performance is not affected by transient contact with oil, water or steam. A variety of temperature ranges is available up to a maximum of 10 levels per strip. They are accurate to ±2% of their stated reading (5 degree increments up to 116 deg C)" (7 quid for a pack of ten).
Next time I go for a drive, these will be stratgically placed on the block, inlet pipe to swirl tank, inlet pipe to rad, outlet pipe from rad etc.
Once I get back, I will be able to see the highest temp reached by each of the components & check against the highest temp shown by the gauge.
Anybody have a feel for the price to get a new sender & gauge fitted & claibrated ?
The problem is that those labels can get affected by the ambient temp under the bonnet. They only tell you a maximum as well and you don't know when that occurred.
All you need to do is start the car up, and take readings as the car gets hot. You can zap away and get a really good feel of what is going on. It will quickly get to fan switching on temps and you can see what is going on. Remember keep things simple.
All you need to do is start the car up, and take readings as the car gets hot. You can zap away and get a really good feel of what is going on. It will quickly get to fan switching on temps and you can see what is going on. Remember keep things simple.
Steve, agreed, but they are purely an interim test costing 12 quid inc p&p rather than 50 quid for an infrared thermometer.
If nothing else, they should help prove that the maximum temp reached by any component was 'x' wheras the gauge said 'y'.....
As a strategic solution the car is booked into Castle TVR for Sat 15th May, for test & re-fit of temp sender (the cost of the temp indicator strips + Castle TVR = price of infrared thermometer).
If its the gauge at fault then unfortunately it would appear to be a factory order, which probably means I won't have it fixed pre the long hot drive to Le Mans
If nothing else, they should help prove that the maximum temp reached by any component was 'x' wheras the gauge said 'y'.....
As a strategic solution the car is booked into Castle TVR for Sat 15th May, for test & re-fit of temp sender (the cost of the temp indicator strips + Castle TVR = price of infrared thermometer).
If its the gauge at fault then unfortunately it would appear to be a factory order, which probably means I won't have it fixed pre the long hot drive to Le Mans
Now theres definitely a post missing here.. I'd just been off sharpening my Crayons for you and it seems Steve has filled in since my post.
OK, a low tech solution for those without a laser thermometer: If I were you I'd spark up the engine and keep an eye on the guage with the top off the swirl pot (as mentioned).. you will immediately see/hear when the thermostat opens, and can check that against the guage reading as it happens. Then put the top on the SP and wait for the fans to come on, note the temperature guage reading again.
Assuming (leap of faith here) that the Thermostat and Otter switch are working ok, you will have points for 78 and 92 degrees in your head as per what the guage is saying. (assuming you still have the standard 92 degree otter.) How does that match with the guage readings..? ..this will give you some idea of how well it is working.
If the guage reads 100 when the fans come on (which for the sake of argument is 92 degrees) then this would suggest 110-115 is more like 102-107, which whilst not ideal is in the realms of "normal" for a stuck in traffic moment.
A simple "fix" which reduced the peak temperature when stationary on mine was to use a lower temerature Otter that switched on at 85 degrees.. can't rate it high enough..
Cheers
Matt
>> Edited by M@H on Tuesday 20th April 12:28
OK, a low tech solution for those without a laser thermometer: If I were you I'd spark up the engine and keep an eye on the guage with the top off the swirl pot (as mentioned).. you will immediately see/hear when the thermostat opens, and can check that against the guage reading as it happens. Then put the top on the SP and wait for the fans to come on, note the temperature guage reading again.
Assuming (leap of faith here) that the Thermostat and Otter switch are working ok, you will have points for 78 and 92 degrees in your head as per what the guage is saying. (assuming you still have the standard 92 degree otter.) How does that match with the guage readings..? ..this will give you some idea of how well it is working.
If the guage reads 100 when the fans come on (which for the sake of argument is 92 degrees) then this would suggest 110-115 is more like 102-107, which whilst not ideal is in the realms of "normal" for a stuck in traffic moment.
A simple "fix" which reduced the peak temperature when stationary on mine was to use a lower temerature Otter that switched on at 85 degrees.. can't rate it high enough..
Cheers
Matt
>> Edited by M@H on Tuesday 20th April 12:28
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