cliff.b Posted May 17, 2021 Report Share Posted May 17, 2021 My Spitfire 1500 has always made a short squealing sound when blipping the throttle, changing down for corners etc. Decided it was probably the fan belt slipping but already as tight as I was happy with. Noticed it had a 4 blade metal fan which I'm guessing isn't right for 78 Spit? So tried taking it off as an experiment & squeal gone. Fan appears to be steel & weighs nearly 0.5 Kg. I'm guessing that a combination of air drag & inertia overcame the grip of the fan belt when there was a sudden increase in revs. Link to comment Share on other sites More sharing options...
johny Posted May 17, 2021 Report Share Posted May 17, 2021 Sounds a reasonable diagnosis but the only thing that worries me is that fan is from a Mk1, 2, 3 Spitfire which used a different water pump from the later models like yours. Hopefully your case is just a fan swop and not the water pump as well but sure somebody will be along soon to tell us if theres any differences... Link to comment Share on other sites More sharing options...
cliff.b Posted May 17, 2021 Author Report Share Posted May 17, 2021 18 minutes ago, johny said: Sounds a reasonable diagnosis but the only thing that worries me is that fan is from a Mk1, 2, 3 Spitfire which used a different water pump from the later models like yours. Hopefully your case is just a fan swop and not the water pump as well but sure somebody will be along soon to tell us if theres any differences... That's interesting. Are the water pumps interchangeable? Link to comment Share on other sites More sharing options...
johny Posted May 17, 2021 Report Share Posted May 17, 2021 The pump bodies and impellor are the same for all of our cars but I know the pulleys can be different both in diameter and offset. Not sure in your case what the differences are... Link to comment Share on other sites More sharing options...
cliff.b Posted May 17, 2021 Author Report Share Posted May 17, 2021 Hmm, I suppose if the pulley was smaller than the one usually used with that fan then It would run faster and that could have been contributing to the squeal. It did seem to shift a lot of air and was quite noisy. I think a smaller pulley would also give less contact with the fan belt. Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 17, 2021 Report Share Posted May 17, 2021 and fan belts grip by the sides of the Vee's if the pulley and belt Vee width/angle/ depth is no matched you will get belt slip no matter how tight you make the belt adjustment a worn belt that sits in the base of the Vee wont transmit any power so some wear tear and pulley vee mis match will cause problems of slip Pete Link to comment Share on other sites More sharing options...
cliff.b Posted May 17, 2021 Author Report Share Posted May 17, 2021 1 hour ago, Pete Lewis said: and fan belts grip by the sides of the Vee's if the pulley and belt Vee width/angle/ depth is no matched you will get belt slip no matter how tight you make the belt adjustment a worn belt that sits in the base of the Vee wont transmit any power so some wear tear and pulley vee mis match will cause problems of slip Pete Yes, I will have to investigate further and also try and find out what the differences are in the pulleys. Link to comment Share on other sites More sharing options...
johny Posted May 17, 2021 Report Share Posted May 17, 2021 yes Im not saying that youve must have a non standard pump as the earlier fan might fit perfectly on the later pump. Looking at Rimmers site your pump pulley diameter should be bigger than the casing while on the early one its the other way round. If this is confirmed I would get the correct 7 blade plastic fan which should be more effective and quieter... Link to comment Share on other sites More sharing options...
cliff.b Posted May 17, 2021 Author Report Share Posted May 17, 2021 46 minutes ago, johny said: yes Im not saying that youve must have a non standard pump as the earlier fan might fit perfectly on the later pump. Looking at Rimmers site your pump pulley diameter should be bigger than the casing while on the early one its the other way round. If this is confirmed I would get the correct 7 blade plastic fan which should be more effective and quieter... Thanks for looking into this. I'm thinking now I may fit an electric fan. Link to comment Share on other sites More sharing options...
johny Posted May 17, 2021 Report Share Posted May 17, 2021 What ever you do dont ask if an electric fan is a good idea! Link to comment Share on other sites More sharing options...
cliff.b Posted May 17, 2021 Author Report Share Posted May 17, 2021 33 minutes ago, johny said: What ever you do dont ask if an electric fan is a good idea! Ha ha, yes, I have read some of the previous threads about that. Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 Rightly or wrongly I have decided to go electric and fitted twin 9" fans in front of the rad The one on the right (from the front) is connected to the thermostat which can be adjusted while driving. The other fan can be switched between off, thermostat or permanent on. Most of the time this fan is blowing relatively cool air which plays nicely on the carb area and can be switched on as required. Link to comment Share on other sites More sharing options...
johny Posted May 29, 2021 Report Share Posted May 29, 2021 Well if that doesnt keep things cool the problem lies elsewhere☺️ Which thermostat/controller have you installed? Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 23 minutes ago, johny said: Well if that doesnt keep things cool the problem lies elsewhere☺️ Which thermostat/controller have you installed? Standard capillary thermostat into bottom hose with control knob in cabin, some custom switch stuff I worked out and 2x fused relays next to the battery. When the door is closed you can't see the control knob but I can still adjust it if required. Link to comment Share on other sites More sharing options...
johny Posted May 29, 2021 Report Share Posted May 29, 2021 Looks good and Im surprised the thermo capillary reaches that far! Will a fan run on after the engine stops - its quite nice but makes me nervous Im going to come back to a flat battery😳 Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 15 minutes ago, johny said: Looks good and Im surprised the thermo capillary reaches that far! Will a fan run on after the engine stops - its quite nice but makes me nervous Im going to come back to a flat battery😳 The capillary tube actually has a bit of slack, just need to give some thought to how you run it. I took it out through an existing hole in the bulkhead directly in front of where it is fitted, behind the brake & clutch masters & down the RHS to the lower hose. The electrics go down the LHS, cable tied to the existing loom. The fan will stay on as long as the ignition is on but as the mechanical fan stops when the engine does I thought it wasn't too important to have a run on. Link to comment Share on other sites More sharing options...
johny Posted May 29, 2021 Report Share Posted May 29, 2021 Yes my Vitesse had hot restart problems so now the fan runs on to reduce the residual heat that comes out when stopping from a high speed run. Ive watched the temperature gauge after stopping and the fan works well to control the overshoot (the coolant keeps circulating by thermal circulation) plus the flow of air stops carb heat soak... Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 27 minutes ago, johny said: Yes my Vitesse had hot restart problems so now the fan runs on to reduce the residual heat that comes out when stopping from a high speed run. Ive watched the temperature gauge after stopping and the fan works well to control the overshoot (the coolant keeps circulating by thermal circulation) plus the flow of air stops carb heat soak... Yes, I could easily rig it to do that if I find that it's a problem. Link to comment Share on other sites More sharing options...
johny Posted May 29, 2021 Report Share Posted May 29, 2021 As a flat battery avoidance measure I took the power supply through a thermal switch mounted on the radiator so even if the thermostat sticks on when the rad cools to 85º it cuts the power👍 Link to comment Share on other sites More sharing options...
DanMi Posted May 29, 2021 Report Share Posted May 29, 2021 The fans are totally interchangeable, a 78 spit would have probably had a viscous coupling water pump, but that may have been replaced with a standard one. That metal fan is from a mk3 mk 1-2 were 2 blade (in UK). The MK4/1500 had a plastic fan. The early water pump had a smaller pulley as the crank pulley was smaller. Having the metal fan shouldn't cause any problem. Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 1 hour ago, johny said: As a flat battery avoidance measure I took the power supply through a thermal switch mounted on the radiator so even if the thermostat sticks on when the rad cools to 85º it cuts the power👍 You can't buy peace of mind lol Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 41 minutes ago, DanMi said: The fans are totally interchangeable, a 78 spit would have probably had a viscous coupling water pump, but that may have been replaced with a standard one. That metal fan is from a mk3 mk 1-2 were 2 blade (in UK). The MK4/1500 had a plastic fan. The early water pump had a smaller pulley as the crank pulley was smaller. Having the metal fan shouldn't cause any problem. I'm sure you're right. Pretty sure the MkIV I had all those years ago was a plastic fan. However, I'm not changing it back now 😁 Link to comment Share on other sites More sharing options...
johny Posted May 29, 2021 Report Share Posted May 29, 2021 7 minutes ago, cliff.b said: You can't buy peace of mind lol Yes you can, cost me a couple of quid for the thermal switch🤗 Link to comment Share on other sites More sharing options...
cliff.b Posted May 29, 2021 Author Report Share Posted May 29, 2021 3 minutes ago, johny said: Yes you can, cost me a couple of quid for the thermal switch🤗 Ha ha Link to comment Share on other sites More sharing options...
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