That is a reasonable question. I have not seen any surfire way of confirmation. There is some anecdotal evidence.the coolant pump on the Universal MX25 engine is working correctly?
Several things I pondered as I read your post.What I've observed is that the water temp comes up to around 170 and surges to around 180. It didn't use to do that.
….something as simple as the thermostat aging…..
Normally is a cooling pump is not performing something over heats.
Mine is reading 160 degrees at 1800 RPMs and 165 at 2200 RPMs. It was reading ~10 degrees higher when I purchased the boat, but I replaced the seals on each end of the heat exchanger (they were very deteriorated--both seals, the 0-ring for the bolt and the flat round seal for the end) and replaced the Zinc (clearing out the sludge from where the PO hadn't changed it in a season or two) and that dropped my temp ~10 degrees. I've been holding steady there for 5 years, replacing the zinc every year.I've seen intermittent brief surges in coolant temperature. I've replaced the impeller on the raw water pump and can even observe the flow momentarily on the output of the water pump to confirm its pumping. For the coolant pump, I've bypassed the hot water heater connections when I replaced it last year, so I can't confirm, but maybe I should reconnect that as it would make this easier to confirm. I don't believe there's air in the system as I bled it briefly. What I've observed is that the water temp comes up to around 170 and surges to around 180. It didn't use to do that. Possibly related, I've seen a handful of times when the tach drops to 0 when the engine is running. I'm thinking it may be a ground issue as well. Any tips on how best to connect the hot water heater coolant lines up and bleed the system?
engine seems to run fine... just the instrument acting weird... dropping to zero... seems like its heat related... works fine for a while, then 0... next time i use it a day later its fine.Oh, and is just the tach needle dropping, or is the engine actually starting to stall? If you have intermittent stalling, please read this post where I was experiencing that and what the solution was.
I have had similar issues with my tachometer , it needs a certain amount of voltage from the alternator before it will start reading. if the battery is fully charged the alternator will only put out a minimum amount of volts. I have a solar panel also, and I have to shut that off so when I am motoring so the alternator will continue to put out enough volts, I do not remember what the minimum volts is to activate the tachometer. Your description is very similar to my issue. I use an external regulator for my charging from the alternator.engine seems to run fine... just the instrument acting weird... dropping to zero... seems like its heat related... works fine for a while, then 0... next time i use it a day later its fine.
I don't think a faulty thermostat would cause the needle to jump around like it does in your video. As JoeWhite suggested probably wiring or a faulty sender. Maybe a bad gauge?Thanks, I'll check the connections and see if that's the cause.
I'm also thinking it might be related to the thermostat? Anyone have experience diagnosing a bad thermostat? I do have an oem replacement part handy. Any tips on changing it out?
True but much easier to diagnose it with temperature gun readings from various points on the engine.You can pull the thermostat. put water on the stove in a pan. Heat it up. Use a thermometer to test the temp of the water. At 150º the thermostat should open (depending on the unit). By 180º it should be fully open (again depending on the unit).
Where is the fun in that? Beside, you might miss the opening and closing temps of the thermostat.much easier to diagnose it with temperature gun readings from various points on the engine.