'88 2.3L doesnt warm up in cold temps

[justin_steube]

My engine refuses to warm up when its cold out.

When the temp is around 60 or so, the temp gauge reads just above the 'C' and will blow warm air - when its hot out (90+) the truck stays cool, and wont overheat even when im stuck idling in traffic. Once it gets much colder than 40 out, my engine just refuses to go above the 'C' on the temp gauge and wont blow any warm air at all...

I have replaced the thermostat (twice), water pump, radiator hoses, and flushed the radiator and heater core. Any ideas on where to go from here? Winter is approaching quick and I dont want to go through another one heatless. It sucks real bad.

thanks in advance!

 

[warrpath4x4]

have you verified with a manual gauge or heat gun what temperature your thermostat housing is at?

are the hoses getting hot?

how did you flush your heater core?

best way I have found to flush the heater core.
1) find out which heater hose is your hot one and which is the cold one.
2) disconnect the cold hose from the core and the hot hose (after it has cooled down) from the engine side.
3) poor a little water into the core.
4) use a shop air compressor and put an open chuck in the hose and crimp the hose with a pair of pliers.
5) shove the open air chuck in the heater core hose with a firm grasp on the air hose, release the pliers.
6) watch all the junk fly out of the heater core.
7) repeat until the water coming it is clear.

 

[tomw]

Get the engine to its working temp, and touch the upper radiator hose to determing how hot the coolant is. Now, touch BOTH heater hoses. They should both be close to or hotter than the upper radiator hose. Likely one is hot and the other more tepid. If so, replace the heater core. Some systems shut off the coolant flow in warmer weather, to reduce A/C load from a hot core next to a cold evaporator. That will let the coolant sit and stew, get mad, and decide to turn to sludge. Sludge will restrict coolant flow, allowing only some to flow through the passages that are not blocked.
Your heater core replacement is a 1/2 hour job. You need to lower the coolant level enough to prevent it all flowing out the heater hoses. Disconnect the hoses. If they stick, slit them with a knife, or twist with pilers. You do not care about the old heater core tubes. Remove the glovebox door, and look up and a bit leftward. There is a removable cover, held on by a couple sheet metal screws. Remove it. The heater core will peer back at you, coldly. (ha,) Slide it out and manipulate it through the glove box opening or behind the lower edge of the dash. Slide in the new core. I poked around and used a flash light to remove any bugs, leaves, and other detritus before sliding in the new core. Replace the cover and glove box. Re-connect the heater hoses.
Re-fill the coolant to the proper level. Start and run the engine to temperature, and bleed any air bubbles out of one of the heater hoses by loosening the clamp, sliding the hose off(arch the hose to get the air to the 'top') and letting the air out. Slide hose back onto the heater core tube. Tighten the clamp, and the radiator cap. Drive a while and check level in the expansion tank. Add as necessary.
Check the heater core hoses, and I bet they both are about the same temperature.
tom