Thanks for the advice edb,i am getting new rubber o rings for under the rocker cover bolt washers to hopefully keep the water out,the old ones are pretty rotten.What is the best way to test if the thermostats are working.The dozer seemed to be working at normal temperature when it was going.Cat apparently do not make the correct thermostat part number 4H1991 anymore but looking online i have found an alternate number 9S3808,can anyone tell me if this is the correct replacement part number for it.
cheers John.