K-Series engine temp rising

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samsul
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Hi,

Looking for a bit of advice on the cooling system again, sorry!

I have concluded that the dash gauge misreads so no longer rely on it. Instead I run around with an OBDII reader plugged in relaying live data.

Based on the OBD readings, the car generally runs between 71C and 77C. I suspect this is a little low but not sure?

On a run last weekend the coolant temps were within usual operating range (70s with the odd foray into the low 80s whilst sat at lights). However, when I pulled onto the drive I let the car idle to see if the temp would peak and then stabilise. Within 2 mins the OBD reading hit 92C before I bottled it and shut the engine off. There was no sign of the temp levelling off.

Interestingly, there is no issue when moving - even at 10mph where there is limited airflow through the engine bay - the temps drop 4 or 5C within 20 seconds of moving off, even at extremely low speeds.

This is a long-winded way of asking if  (a) I am simply being deceived by my sensor getting heatsoaked and I need to stop worrying and get on with things! (b) there is yet more bleeding to be done to remove an air lock (c) my thermostat or water pump isn't behaving properly at idle?

As background, I have back-filled the heater hoses, filled the radiator to the brim, massaged the pipes, all with the nose jacked up as high as possible.

 

 

 

Jonathan Kay
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Did the fan come on? And is it blowing air in the right direction?

Jonathan

samsul
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Hi - the fan did come on and it blows in the right direction. 

SLR No.77
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... go back to post #11 and move the senders, then you can take the guesswork out of what's going on.

Stu.

Caterham and Lotus Seven Club Leadership Team Member

The register for all numbered limited-edition Caterhams ....... www.thecaterhamregister.net ...... www.instagram.com/thecaterhamregister

Beagler
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The expansion tank cap has a pressure of 115 kpa (16lb/sq in) is the cap functioning correctly. No pressure = lower boiling point of coolant.

2019 310S 1.6 Sigma

samsul
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Hi,

Brand new cap on the expansion tank so can hopefully rule that out.

Bit of a breakthrough...if I hold a steady throttle input when the temp rises at idle I can bring temps down to normal operating range within 20 seconds. That implies the coolant isn't circulating fast enough on its own so I think I am narrowing the issue down to thermostat or water pump. 

Thanks for all advice. It's getting there!

Jonathan Kay
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"Bit of a breakthrough...if I hold a steady throttle input when the temp rises at idle I can bring temps down to normal operating range within 20 seconds. That implies the coolant isn't circulating fast enough on its own so I think I am narrowing the issue down to thermostat or water pump."

That is interesting. I was trying to think of everything that's different between driving and idling.

Jonathan

john milner
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I may be reading this thread incorrectly but at the start the temperatures were from the dash gauge which is now suspected as giving faulty readings so now OBD readings are being used. Could this be like comparing apples & pears?

When up to temperature my dash reads in the low 80s, rises when stationary and quickly drops when the fan starts or I get moving. I think this is normal but I do not know what normal OBD readings are. I do not have a hole in the thermostat or an additional high point bleed valve.

Any leaks can cause erratic readings as loss of pressure will cause a temperature rise. Heat expansion could temporarily close a small gap, pressure open a gap etc. 

The easiest thing right now is to get the dash gauge working so you have some well known figures to compare with. Most likely this is due to a faulty sensor which is easily swapped out with minimal coolant loss.

Temperature gauge tests https://www.tom-seven.stillgame.ch/Main/CTS_Meter_logic.htm

If the temperatures are still not correct then the most likely causes are trapped air or faulty thermostat. If satisfied it is not trapped air then the thermostat is a relatively cheap thing to swap and a small hole may help with operation and the shifting of bubbles.

If the coolant pump is failing I would have thought there would be some funny noises going on due to bearing failure. Some pumps have plastic blades so an unlikely possibility is some have broken off.

Blocked waterways are at the bottom of my guess list.

david nelson
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I think I may have read this wrong

on start up you get 80 degrees  but after 20 mins if you get stuck in traffic the temp goes up into the 90+ mark

This all sounds normal.

WT on the ECU may not be the same as on the Gauge ( When hot mine are different by 10 degrees.) ECU higher than gauge.

you turn the engine off when it gets in the 90 + temp but the fan will not start till 92 degrees is reached.

My K in traffic would always go up so fitted over ride switch. 

To me all sounds normal. 

getting the remote pipe as in an earlier post may give you confidence all is well as it can be put out of the way of the exhaust. 

 

 

" The Legend" Low flying Oct 2021

 

John Vine
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Re #29:

...loss of pressure will cause a temperature rise.

I don't follow that. Could you possibly elaborate?

JV