Jeff Yost Posted October 16, 2017 Share Posted October 16, 2017 Why does my fv721 fox overheat at about ten miles? Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 13, 2018 Author Share Posted August 13, 2018 How do I know correct/stock muffler from repro? Quote Link to comment Share on other sites More sharing options...
0 Richard Farrant Posted August 13, 2018 Share Posted August 13, 2018 1 hour ago, Jeff Yost said: How do I know correct/stock muffler from repro? I am going by the colour, looks like silver or bare metal. Having worked on the Fox over all their service life, around 1975 to 1990, I recall the silencers being heatproof black. You cannot rule anything out. I suggest you contact the previous owner to find what work had been done to the vehicle before the overheating occured. This could provide clues. Richard Quote Link to comment Share on other sites More sharing options...
0 sirhc Posted August 13, 2018 Share Posted August 13, 2018 Looking at the tail pipe on that silencer it does look like someone has had it made. The original is shorter and has a lip for the ball & cage for wading. Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 14, 2018 Author Share Posted August 14, 2018 I guess I remove the muffler/silencer and drive it. Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 15, 2018 Author Share Posted August 15, 2018 After removing the silencer guard I tapped on the silencer and it sounds hollow. Could that be a problem? Quote Link to comment Share on other sites More sharing options...
0 Richard Farrant Posted August 15, 2018 Share Posted August 15, 2018 7 hours ago, Jeff Yost said: After removing the silencer guard I tapped on the silencer and it sounds hollow. Could that be a problem? If there is an obstruction or restriction in the exhaust system it will not allow the hot gasses to pass out quickly enough. A copy silencer may be different inside and any sound absorbing material inside might have moved. As you are not coming up with any faults in the cooling system, we have to widen the field searching for causes of temp rise. The original silencer was very heavy as I recall. Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 19, 2018 Author Share Posted August 19, 2018 OK. Was going to drive fox without silencer to see if it would overheat. Best I can tell it is homemade and hollow. Took back cover off and observed ware on the edge of the blower motor belt. Thought of test run with cover off to see if it would not overheat. Quote Link to comment Share on other sites More sharing options...
0 Richard Farrant Posted August 19, 2018 Share Posted August 19, 2018 1 hour ago, Jeff Yost said: OK. Was going to drive fox without silencer to see if it would overheat. Best I can tell it is homemade and hollow. Took back cover off and observed ware on the edge of the blower motor belt. Thought of test run with cover off to see if it would not overheat. If I am not mistaken, the photo shows the power steering pump pulley and belt Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 20, 2018 Author Share Posted August 20, 2018 Your probably right. I'm still learning. What do you think about driving with silencer off and back cover off? If it don't over heat then it might help narrow it down? Thanks for the help Quote Link to comment Share on other sites More sharing options...
0 sirhc Posted August 20, 2018 Share Posted August 20, 2018 He’s not probably right, he is right. There are 4 belts in that area: water pump, power steering pump, alternator & fan drive. You need to have a proper look and make sure they are all there and in good condition. The one in the photo doesn’t look great. Quote Link to comment Share on other sites More sharing options...
0 Richard Farrant Posted August 20, 2018 Share Posted August 20, 2018 6 hours ago, Jeff Yost said: Your probably right. I'm still learning. What do you think about driving with silencer off and back cover off? If it don't over heat then it might help narrow it down? Thanks for the help You will find the noise from the open pipe is far to great to go on the road with, although it sounds great (!). When we tested the Fox's after repairs we always left the rear armour off to check for leaks and had a short silencer made to fit the outlet on side of the hull, think it was one from a V8 Rover, you will need something on there. My thoughts are that there is a possiblity tthat sound deadening material in your silencer may be obstructing gas flow, how ever it seems you have not confirmed all the belts are intact yet. Quote Link to comment Share on other sites More sharing options...
0 Newcoregon Posted August 20, 2018 Share Posted August 20, 2018 Hi; My Fox overheated because previous owner bored out the sleeves and installed high compression car pistons... a real mess now. Later Newc Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 20, 2018 Author Share Posted August 20, 2018 How long did it take to overheat? I'm going to address the silencer at this point. Quote Link to comment Share on other sites More sharing options...
0 Newcoregon Posted September 8, 2018 Share Posted September 8, 2018 Fox overheated straight away. Rads had been serviced and all, seems correct... except the incorrect engine modifications caused excessive heat transfer to eng block. The sleeves are important in the first series eng, and the high compression car pistons just made it all worse. I have a later series eng core to rebuild and install... someday? Newc Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted April 25, 2019 Author Share Posted April 25, 2019 Now that winter is finally over back to work on the fox. Curious if heat exchanger restriction could be possible. Going for a test run soon with out back plate and going to monitor transmission temp. Also am I paranoid about driving at 225 degrees when the manual says do not hard run engine and exceed 240 degrees? Quote Link to comment Share on other sites More sharing options...
0 Newcoregon Posted May 6, 2019 Share Posted May 6, 2019 Well; I haven't run my Fox in 3 yrs, old petrol now. Understand that overheating was always iffy. My problem is a bad rebuild on a series one engine.. Series 3 engines had far better cooling passages and even the heads do not interchange. Newc in Oregon USA Quote Link to comment Share on other sites More sharing options...
0 Terra1936 Posted August 6, 2019 Share Posted August 6, 2019 Did you fix your problem? Quote Link to comment Share on other sites More sharing options...
0 Jeff Yost Posted August 7, 2019 Author Share Posted August 7, 2019 Drove it maybe ten miles with the back plate off. Seemed to help? Got up to almost 215 degrees at high Rpms. I'm convinced low speeds are fine. Making a vented back engine cover for a 12 mile test run to annual show. Manual says to pull over at 240 degrees. Seems a little hot. Quote Link to comment Share on other sites More sharing options...
0 Terra1936 Posted August 7, 2019 Share Posted August 7, 2019 Did you ever bleed The air out? Quote Link to comment Share on other sites More sharing options...
0 Terra1936 Posted August 7, 2019 Share Posted August 7, 2019 Have you used a laser thermometer to verify your gauge is correct? Quote Link to comment Share on other sites More sharing options...
0 Terra1936 Posted May 28, 2021 Share Posted May 28, 2021 Did you give up? Quote Link to comment Share on other sites More sharing options...
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Jeff Yost
Why does my fv721 fox overheat at about ten miles?
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