1996 blazer. radiator fluid looks like mud. It has always looked like mud and its been through two radiator replacements, and two flushes. And it still is mud colored. Could it be the Heater core is rusted out and causing the fuild to change color everytime? NOTE: Heater core is not leaking yet.

Secondary issue. Temperature gauge in cab runs up to redline when blazer first warms up and then drops back to about 200 degrees. I have replace thermostat 3 times and had temp read using temp guage. It never reads as hot as inside guage says. Bad guage inside?

HELP

Tim

 

Your second issue is likely caused by a problem with the temperature sending unit for the gauge. On a 96, there are two sensors or sending units. The one for the PCM is a multi wire sensor and I think it is the one that is located just below the thermostat. The one for the gauge should be a single wire gauge which is located in the driver side head between cylinders 3 and 5.

On the first issue, sounds like you have some pretty good active corrosion going on in the engine block. Were the flushes done with any chemical additives to aid in the loosening and removal of build up rust scale? If not, that is what I would look into. Vinegar can be a good rust remover (I use it for rust removal on parts from my Chevelle and Blazer) and can be used as a DIY rust remover agent in the cooling system. You just have to be very thorough about flushing the system. Professional flush jobs should be of the chemical kind and should only have to be performed once or twice before the system is clean. A flush should be of the full system, including the heater core. The heater core is typically done separately, but should never be forgotten.

Many of the new coolants are not very effective at prohibiting rust once an active state of rust has been reached. The only choice is to get all of the rust out of the system and often that means some kind of chemical additive to make the process faster.