overheating!

[renneking]

1999 ranger is overheating. changed thermostat since was cheap,flushed system because coolant looked rusty and did a pressure test which showed no leaks. fan also looks good. getting heat about every other start but no coolant on floor board so not sure about heater core. not even sure if bad heater core can cause overheating? after flushing system doing pressure test and changing oil truck still overheats and now idles very rough as if about to stall. i am clueless, just trying to avoid big mechanic bill so any help would be greatly appreciated.

[martin]

first thing that comes to mind is head gasket (do compression test) or water pump.

[renneking]

no one really seems into this one but i'll through it out there anyway. did pressure test, no external leaks. did the test for internal leaks i.e. blown headgasket, no leaks. did block test with the suction device put onto radiator that would turn dye yellow if leak, no leak. get heat in cab sporadically but when it works is very good heat. weep hole on water pump is not leaking but not sure if i can feel flow through upper radiator hose. should the flow be very strong and noticable. should i be able to squeeze upper hose easily with thermostat open. last week would start to overheat in about 2 miles. drove tonight for about 3 miles and could not get it hot. i guess what i'm asking is how do i know if it is for sure the water pump or possibly a plugged radiator or whatever else. just trying to save a buck so any help would be greatly appreciated.

[backroad101]

Pull the in and out hoses off the heater core connections on the firewall, then flush and back-flush the heater core. While the hoses are disconnected, connect them them to each other to bypass the heater core and drive around to see if you overheat. If no, then it's the heater core. If yes, problem elsewhere.

Connect the hoses back to the heater core and drive again. If no overheat, your flush / back-flush worked. If no issue is heater core or elsewhere.

Other option is you have air in the cooling system

[shane96ranger]

Sounds to me like you have an air pocket. Did you put the "pellet" in the thermostat at 12 o'clock? This helps bleed the system of air pockets.

Is your gauge sweeping back and forth, or just staying high?

[hondaxr650]

If your coolant was really rusty, you may have a clogged radiator. I've also seen cars with rusty cooing systems that had the fins completely rusted off of the water pump impeller. Just a thought.

[renneking]

thanks for the replies. coolent was very rusty and havent flushed heater core yet. not sure about thermostat "pellet" being at 12oclock. just got off work going to go try some of this out.

[kimcrwbr1]

If you dont know how old the water pump is get a new one. The only way to get all the rust out of the block is by pulling the water pump and t-stat. With high pressure water flush the block out good until you get no brown water also blast the heater core both ways about half pressure and do the same with the radiator until you get no brown water. Spend the money on a good water pump and t-stat. If you have the time fill the radiator and heater core 1/2 bleach 1/2 water and let sit overnite then rinse good with water. To fill the systen add a flushing tee in the heater hose that goes to the t-stat housing hold it level with the top of the radiator and pour in the coolant/water until it comes out the radiator that will fill the heater core and bypass and with the weep hole on the t-stat at the highest point you should only need to fill the overflow tank after the engine comes up to normal temp.

[shane96ranger]

Dumb question, but you did put the thermostat in the right direction as well, right?

[shane96ranger]

Originally Posted by kimcrwbr1

with the weep hole on the t-stat at the highest point

Renneking, this is the same thing I was talking about. The part we are talking about is the little brass piece that jiggles around, almost to the edge most outer diameter of the t-stat. The OEM t-stats have a little BB/pellet in it.