No Heat 1997 Blazer

My daughter's 97 Blazer 4.3 vortec was not heating very well, the temp gauge barely went over 110 and very little warm air. Based on what I read in this forum. I installed a new non-AC Delco radiator cap, and put in a new thermostat for good measure..and sure enough now I have heat and a temp gauge that moves up close to 180-200 or so then the thermo opens and it drops back to 140-150 or so. I assume I am okay.


I am looking for advice on the heating/cooling system in general. It seems to me like the ventilation fan doesn't run/push as much air as I would expect. On the lower 2/3rds of the speed settings the fan sound is barely audible and air movement is negligible. Should it be moving more air/faster? Could I have a problem with a fan resistor. Over the past year there have been times where the fan wouldn't run at all. i.e set for AC in the summer fan on high..no fan.. start to drive and 30 seconds later fan comes on by itself?

Also I have read some of the threads/postings on Dex-Cool. I did notice some small sludge particles around the cap and neck of the radiator, and some breaking down of the gasket on the cap. The coolant that I could see in the radiator looked fine. I did not see any thing but clear coolant when I pulled the thermostat. In fact the thermostat may have been okay...because when I pulled it a small quantity of coolant gushed out of the manifold and it was all clear.

Does it sound like I would have any sludging elsewhere in the engine/heater core to worry about? We bought the blazer 2 years ago and it was serviced by the dealer at that time with new anti-freeze/flush at that time, this is the first that I have gone into the system

I would appreciate anyones input on both of these questions.

Spit

Also, it sounds like your fan is shot. If the resistor pack is gone, the fan will never work.

I would replace the fan, it is really cheap and easy to swap in.

With the new rad cap on, the system will eventually clear out all the air in the system.

I've had quite a few experiences with heat in my 99 Blazer.
Can't comment on your fan but if you had some sludge around the rad cap its likely sometime in the cars history the reservoir may have run dry and some air found its way into the system.

For this moment going forward it is important that you keep the coolant reservoir full ... always.

To maybe fix any heater problems I would advise that you just backwash your heater core. If you blow out all the debris into a pail you will quickly see if there is any scales or sludge there. I had to do this a half dozen times last year and this year the heater is fine. I just used a garden hose some couplings and quick connects and a few extra pieces of heater hose to connect to the fire wall.

The whole process takes 20-30 minutes and may need to be repeated every few weeks or so until the trouble finally clears

Some will advise a complete system flush but my experience with this is that a lot of debris never gets flushed out but its loose and eventuslly plugs things up in about 1-2 weeks. Good results are obtainable with just a heater flush.

Good luck