Cooling issue.
Posted: Sun May 26, 2019 6:52 am
Any thoughts on this issue would be appreciated.
The problem is one of generally running at a higher than usual temperature and overheating when the engine is stressed.
The engine was built in 2015, however the water pump was not replaced as it was said to have been fairly recent in the donor front cover. It looked and felt fine.
During 2016 and 2017 the cooling was fine under all conditions, including track days. If anything it seemed too efficient as the engine tended to struggle to get above 75deg on, for example, light motorway load. It never exceeded 85deg under any other conditions. The gauge reading was confirmed by the ECU reading.
Early in 2018 I noticed that, suddenly, it was generally running at 85deg and could reach 95deg on a motorway run. At Castle Combe 2018 it overheated after a few laps, expelling lots of coolant at about 110deg. I put some radweld in just in case a radiator leak had occurred, however this made no difference to subsequent runs, so continued with the day restricted to 3 laps then a cool down break. I drove back to Scotland at a steady 70mph with no further problems although the coolant temperature was around 90 deg. The car was fine for normal use the rest of the year, although running at the new higher 85deg. No water loss. No oil contamination.
For this year, the radiator was checked by a repair shop and the top seam resoldered, it was otherwise deemed fine. The hoses are 2015 and no leaks. I renewed the thermostat as a test although the existing one appeared to test fine.
This year I have exactly the same symptoms.
So under normal running conditions the cooling capacity appears to be at it's limit and any additional load results in overheating. I considered the possibility that the cooling system was being pressurised, pushing water out, then overheating, however further testing has proven this is not the case. The overheating occurs first, then water loss results. If the engine load is pushed up, the temperature rises, however if the load is immediately reduced it gradually cools and there is no water loss.
I am now of the opinion that poor circulation is the problem and that this can only result from a partial blockage or lack of pump pressure. Since the radiator, hoses and thermostat have all been checked and the block thoroughly cleaned before the 2015 build, and the change in running temperature in any case occurred abruptly, this only seems to leave the water pump as the culprit. There is no leak from the pump and it's rotation feels smooth.
So my question is, what could occur with the water pump that would result in a sudden loss of performance. Could the impeller be slipping on the shaft. Could the shaft have fractured. It seems too simple an assembly to fail (apart from bearings and seals)
Any ideas?
Dougal.
The problem is one of generally running at a higher than usual temperature and overheating when the engine is stressed.
The engine was built in 2015, however the water pump was not replaced as it was said to have been fairly recent in the donor front cover. It looked and felt fine.
During 2016 and 2017 the cooling was fine under all conditions, including track days. If anything it seemed too efficient as the engine tended to struggle to get above 75deg on, for example, light motorway load. It never exceeded 85deg under any other conditions. The gauge reading was confirmed by the ECU reading.
Early in 2018 I noticed that, suddenly, it was generally running at 85deg and could reach 95deg on a motorway run. At Castle Combe 2018 it overheated after a few laps, expelling lots of coolant at about 110deg. I put some radweld in just in case a radiator leak had occurred, however this made no difference to subsequent runs, so continued with the day restricted to 3 laps then a cool down break. I drove back to Scotland at a steady 70mph with no further problems although the coolant temperature was around 90 deg. The car was fine for normal use the rest of the year, although running at the new higher 85deg. No water loss. No oil contamination.
For this year, the radiator was checked by a repair shop and the top seam resoldered, it was otherwise deemed fine. The hoses are 2015 and no leaks. I renewed the thermostat as a test although the existing one appeared to test fine.
This year I have exactly the same symptoms.
So under normal running conditions the cooling capacity appears to be at it's limit and any additional load results in overheating. I considered the possibility that the cooling system was being pressurised, pushing water out, then overheating, however further testing has proven this is not the case. The overheating occurs first, then water loss results. If the engine load is pushed up, the temperature rises, however if the load is immediately reduced it gradually cools and there is no water loss.
I am now of the opinion that poor circulation is the problem and that this can only result from a partial blockage or lack of pump pressure. Since the radiator, hoses and thermostat have all been checked and the block thoroughly cleaned before the 2015 build, and the change in running temperature in any case occurred abruptly, this only seems to leave the water pump as the culprit. There is no leak from the pump and it's rotation feels smooth.
So my question is, what could occur with the water pump that would result in a sudden loss of performance. Could the impeller be slipping on the shaft. Could the shaft have fractured. It seems too simple an assembly to fail (apart from bearings and seals)
Any ideas?
Dougal.