Only overheats on days over 80deg, We changed the thermostat and antifreeze. The fan is working, No water in oil and we are not loosing any antifreeze. we also have a new radiator cap. Any ideas??? Thanks
Random thoughts in order of how easy they are to check, based on what you mention above has already been done. External radiator condition (Have you pressure washed it? Is there a cooler right in front of the radiator? Ifso that cooler will need to come off to properly clean the rad externally) Fan belt Part Number (Is it genuine or will fit? Is the wedge angle correct?) Fan belt condition & tension Condition of fan pulleys & tensioner mechanism Any belt squealing if you increase RPM rapidly from Idle to High RPM? With a heat gun check the temp of the hoses entering & leaving the radiator. A radiator in good condition you're looking for around 12DegF of difference. Substantially less than that and either the radiator is either plugged internally or the water pump is on the way out.
I will check the belt/tension today and the temp with a gun tomorrow. We have washed the radiator exterior and flushed the interior (hose water) but did not remove the cooler. Thank you very much for the tips!
I scarce dare doubt the Nige on high, but didn't you mean "substantially MORE than that and the radiator is plugged internally or the pump is bad"? less than that would indicate the radiator is plugged externally or the fan is slipping (assuming the hoses are both hot and machine is running hot).
Noooooooo......... think about it. The combination of a radiator in good internal condition and a pump that's working well will cause a significant drop in temperature between the inlet hose from the thermostat housing and the outlet hose at the bottom of the radiator, generally around 12DegF. At the end of the day that's what you want it to do, suck heat out of the coolant. A radiator that's plugged internally will not extract so much heat from the coolant as it passes through it and so the temperature difference between the 2 hoses will be significantly less than the 12DegF optimum. In practice it could be less than half that, which would point to internal blockage.
That would be a large radiator that has build up on the inside of the tubes but not restricted flow (something I don't have experience with). If it had internal blockage wouldn't the circulation be slowed down and the temperature drop be higher? If I squeezed every tube in a radiator (or broke most of the fins off the impeller), the flow would go down and the temp drop would go up. If I placed a mat off debris over the radiator or removed the fan, the temp drop would go down to virtually nothing. I know you're the expert Nige, and I'm looking at this more from a HVAC perspective (that's boilers/hot water heating) than any experience with heavy equipment overheating, but I still think you're half cocked on this one.
What happens in my experience is that even quite significant amounts of internal tube blockage will not drastically reduce the flow - unless the tubes are almost totally blocked off that is, but in that case the engine would be overheating constantly. Scale/contamination buildup on the inner surface of the tubes will however greatly reduce their heat transfer capacity and so the temperature drop between the incoming and outgoing coolant will be less in a partially-plugged radiator than a new one with no scale buildup. Also due to the reduced total cross-sectional area of the inside of the tubes the coolant flow speeds up (all other things being equal) and the result of less surface area and a faster flowing fluid gives a smaller temperature difference between inlet and outlet. That's what I was trying to get at. You're quite right that you could close off a % of the tubes completely (from memory it's up to 10% on conventional radiators) and the radiator would still be sufficiently efficient to keep the engine cool. That's why my suspicion in this case would be internal plugging/scale deposits if all the external factors affecting cooling system efficiency have been checked and found to be OK.
To follow up (I know it is late) the radiator had a lot of dirt etc on the engine side where it could not be seen easily. We power washed it and this helped the issue dramatically. Simple stuff. Thanks
Doesn't matter how late the feedback comes regarding how a problem was solved, it's always welcome. Glad it was something so simple to fix. Did you have to separate the radiator from the cooler to get at it for cleaning..?