i was driving my truck today and all of a sudden i looked and the temperture gauge was going up and down the temperture gauge would go almost up to the red line and then back down to normal and back up and down and would keep doing that the whole way home what could it be? i put radiator stop leak in it yesterday cause it was leaking could that be it?

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97 ford ranger extended cab 4X4 4.0[sold]
1999 ford f150 extended cab 4.6 3 inch body lift 35 inch tall goodyear wranglers 4X4 straight pipe
1998 ford mustang V6 3.8l automatic
mainly stock except high performance headers, performance chip,flowmaster delta 40 series muffler

Sounds like maybe your thermostat had an adverse reaction to the stop leak. Stop leak is not an adequate fix for a bad radiator. It can cause damage elsewear, as a temporary fix yes a repair no.

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'88 STX Super Cab 4x4
2.9 5spd 180,000 miles
Crappy Paint, Worn Parts,
Fix'em as they Break
when Nowhere is Now Here

also low coolent can cause that

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1992 ranger 5.0 5 speed 373 gears makes a fun toy
1998 ranger x cab v8 conversion ohc crown vic dome light explorer sport gauges mp3 20% tint clear dimond head lights smoked tails 16'' mustang wheels flowmasters tano