temp gague jumping around while driving

[jdt10768]

last week replaced cooling hoses and thermostat. hoses needed replacement, and t-stat, why not? so afterward my temp needle is jumping all over the place while driving (after getting warmed up). The needle settles and does not move at idle, and seems to read correctly. a bit high, but it's hot as hell outside right now. I cleaned off the brown ground/earth wires at the front/left of the car. what next?

[c.d.iesel]

make darn sure you don't have air pockets in the cooling system

Jack up the front of the car - WAY UP high in the nose

heater on full hot. remove the rad cap - top up when hot and idle speed

leave room - 2" down from the filler cap neck

if the needle is still dancing - you got instrument cluster

poor connection issues - tons of writeups on the subject

[jdt10768]

will do, ty

[TKMad]

Try a search.

NOW!!!!!!!!!!!

More not helping from the resident lunatic.

I had this problem earlier and it was the connection between the wire and the connector at the temp sending unit. Make sure the connector it tightly gripping the spade on the sender and not loose at all.

[rover1]

very commen problem mine jumps if i slame the door hard or go over bump.

[EscapeArtist]

This can also happen if you have a bad or weak ground on the main ground strap from the battery to the engine block. I had this problem and when I replaced the ground strap it was gone.

[Mike Self]

then I would suspect (as previously noted) air pockets in your cooling systmem, or a sending unit with either a bad + connection or a poor ground. First clean the terminal on the sender that the wire plugs into. If that doesn't work you may need to lower the coolant level a bit, remove the sender unit and clean the threads--both in the water manifold and on the sender. Do not reinstall with Teflon tape or sealer; that's how it grounds. Also as pointed out, check the engine-to-battery & body to battery ground straps.

If this was a pre-existing condition, I would suspect a bad ground at the gauge itself--a common problem. Check archives for easy ways to cure.

cheers

mike

[jdt10768]

had the car on ramps last night and a huge storm blew in, so I have not completed the burping stage yet. And the correct top up level for coolant is 2 inches below the top of the rad neck? Anyone have a pic of the temp sending unit and its location? yes, i did a search first! also, the ground wire near the heater box: where exactly is that connection/ground point?

yes, I am new, so bear with me, ty

[yeewiz]

just fill it to the neck. when the engine heats up and the coolant expands, the excess will push out the overflow tube. would be a good idea to replace the overflow tube to a longer tube that extends below the shelf under the radiator so you don't have overflow collecting on the horizontal shelf

[jdt10768]

may have found the issue. I ran the "raise front / idle / burp" method, and saw a few small bubbles. no major Oktoberfest belches though. But I also found a fairly weak conn (male to female) on the temp sending unit, plus that wire has a bare spot - so I will replace that female connector and trim bad spot from the wire. Thanks for the great info

[jdt10768]

cleaned contact point on temp sending unit, and clamped down on existing connector (was very loose). Drove to work this morning 15 miles and steady as a rock / temp gague at 3 o'clock or just above. Thanks!