As the title states, was working on the 91RS last night, trying to figure out the problem with the heater blowing luke-warm air. Checked the coolant level, at least half empty at the radiator. Filled it back up, started the car and let it warm up, took of radiator cap, no hissing, nothing. Put my hand over the hole for the radiator cap, no pressure. Looked down inside and there is plenty of movement of antifreeze, put back on the cap, checked the coolant lines and could feel coolant running through them as I squeezed the lines. New water pump, new radiator cap, new thermostat 180* slight leak at the thermostat housing but nothing obscene (looks like something slowly ate it away). Any thoughts?

 

I think you are losing coolant and you have to find out why.
Get a pressure tester from AutoZone (or other local parts house) and see if you can find the leak. If you saw a leak at the tstat housing that could do it, I mean it would take a while but you have no idea how long it was leaking. you may have fixed it when you put in the new tstat.

 

Its not just the loss of coolant that bothers me, more like the loss of coolant pressure. If it was getting any pressure to begin with it would have shot out of the thermostat housing a long time ago. There is enough flow to keep the engine cool and it maxes out at 220*F.

 

Your cooling systen will not build pressure if you have the cap off or if it is open anywhere. There is a tool for testing rad caps if you think it might be bad. Psi rating should be marked on the cap. Usually a symptom of a bad cap is temp. fluctuating.

Being that low on coolant will affect your heat problem.

Run the car with the cap on and put your hand on the inlet and outlet hoses of your heater core and compare the two. If there is a big difference in temp. then chances are your heater core is restricted. If you are losing coolant it may be leaking and you might not see it.

 

did you fill up your block at the thremostat when you replaced the engine? chances r that the block doesnt have any water in it so the thermostat cant turn on to allow flow. i bet if you take off the thermostat and fill up the block, you wont have a problem any more.