OK, here's the deal 1990 D350 ,, heat gauge kept going to " H " plus ,, ( 1 ) drain & flush rad. ,, twice .(2) pulled thermostat , put in pan of hot water w/ thermostat @ 200 degrees , opened fully. ( reinstalled ).( 3 ) bought a new coolant sensor ( GENO"S ) , $ 60.00 w/ FEDX shipping .installed sensor gauge went straight to " H " plus ,, put in " DR " set brake , blocked wheels , let run for 40 mins. gauge stayed up on H ( peg'd out ) ,new 100% antifreeze , what me do now ??? Never had this much trouble before. Left plug out behind the therm . let run ( 30 sec. ) water pump ,, pumped out water. Pulled dash installed another heat gauge ,, H - plus ??? CK'd wire to sensor w/ amp probe ,, read 11.48 volts . It seems the heat gauge ( in dash ) gets hot and that is what moves the needle ( guessing here ),, HELP !!!

coffee time ,, whosdunit.

 

Have you used a temperature gun to confirm the engine/coolant is that hot?

 

you could also use the temp gun to see if there are cool spots in the radiator meaning you have plugged tubes. Have you checked the water pump? Some of them have sheet metal vanes that could rust away.

 

THANK YOU FOR REPLYS,, going to pull w/p tomorrow just to make sure ,and flush AGAIN ,and do hot & cold test on the new CTS . Will up date.

whosdunit.

 

New question ??? Before I drain my rad. ,,, I need to get my temp. gauge to return to " C " , I have tried " 3 " different gauges ,, they will all return to 'C " , if I unplug the CTS , plug in sensor wire turn on key " WHAM " " H "+ ???
Have the inst. panel out , how many amps should there be to the 3 prongs that hold the temp gauge ??

whosdunit.

 

Up Date !!!,, as stated earlier , tried 3 different gauges w/ new CTS , all pegged out to " H " , drained rad. down pulled out new CTS, grounded it to the top of mtr. ( just ck'n ) ,nada , OHM tested , cold test & warmed it up test ,, nada .
Lite sanded all the probes on the back of the gauges , nada ,,CK"D GRD'S. ,,nada ,, did I ck. the wiring , 3-4 times all the way to the back of the gauges ,,( pulling hair time ) ,, " THEN " ,, put the " OLD " CTS ,on top of mtr. grounded it pluged it up ,, Wham ,, went to "C " , all 3 gauges ,, ( scratching head ) replaced old CTS , filled'r up , run 30 min. ,, took out for road test , needle went to 3/4 mark , then fell back to 1/4 - 1/2 ,, I still don't know how it fixed " IT's Self " ,, made 2 more trips , goes to 3/4 then back down. I still would like to install a new rad. ,, how are the newer Alum. rad's. ,, any suggestions ,, ??

whosdunit.

 

As recommended before, have you tried a temp gun to check the temp at the cast iron thermostat / filler neck, several places on the rad. and the in and out hoses to see what temps you are getting?

How about installing an after market temp gauge?... As the factory "guess-o gauge" on the dash is know to be almost useless.

Newer aluminum rads you ask? I think they are a big down grade from the OEM brass ones.

Suggestions? Try using sentences with capitol letters and periods, so people can read and understand your posts.
This will get you more and better quality replies / help.