ok i justbought a 99 slt 5.2 had little to no heat at first then replaced t-stat.runs very cool (forgot to ask what temp at advanced auto prob gaveme a 175 or 180temp)flushed and back flushed heater core. no really diff. then yesterday flushed entire system till just water was flowing w/o antifreeze.refilled, now i get little heat at idle but when i rev it up to like 2500rpm i get normal heat coming out.the water pump looks like it was recently replaced. the cores not leaking and when flushing the flow is fine. not leaking from t-stat housing either. heater core supply and return are both hot. do i need a higher temp t-stat???? or water pump due to not enough water pressure ??/? please help just had our first snow fall this morning!!!

 

I've never really had a lot of heat when i just let it warm up in the driveway. The big 4.7L, or 5.2 in your case just doesn't create a lot of heat at idle, its not working all that hard.

I let it warm up in the driveway so that the engine itself is warm, oil is warmed up, pistons aren't cold and slapping around, but the interior never gets warm. It usually takes a few mins of driving.

That's my experience at least, i hope mines not having the same "problem" that yours is.

and 180 t-stat works the best for your motor.

 

I bought my t-stat from advanced did the flush yadyada temp guage sits well 1/4 on up on dash cool heat at idle .gets warm when driving vent doors work fine. I guessing just alot of interior space to warm up.

 

oh yea, forgot to mention that it takes A LONG time to feel the heat in the 3rd row. If it's like -30 out, it'll take upwards of 20 mins of driving to feel heat in the 3rd row.

 

yeah i know it will take a while to warm up the interior but prior to my last flush i was getting no heat at start up and barely warm while driving and sometimes i would get nothing almost cold air .and yeah my temp gauge is around 160*-170* could i put a 195* in to get the temp up more?? or could it be my blower motor resistor assembly not blowing the heat out of the ventsmy 1st and 2nd setting are weak but work ??

 

I had that problem. I had water going around the T-stat. Go to the dealer and get another T-stat water neck $8. Remember theat they are metal and the intake is aluminum so the intake oxidizes and the neck breaks down fast. Replace the water neck and really clean the **** out of your intake manifold. You will have to put a little RTV silicone around the mounting surface between the new T-stat and the intake manifold to make sure no water can get by. Take the new water neck and shave the small **** off of it on the mounting surface before install. You need a good thick T-stat and possibly 2 gaskets or one good gasket that is fatter than regular and install it with a good sealing RTV. (I like the gold.) This will make sure that there is no room for water to get bye. It will force it through the T-stat.

I went through HELL with trying to figure that one out![:@]

 

also use distilled water on the refill... this will ensure that you dont have any sludge building up in the cooling system.

 

thanks ill try a couple of those things and update over weekend