I have a 2000 Nissan Altima. I replaced my water pump and belts and flushed the cooling system. When I put it all back together and started it back up the engine got really hot. Everything was working before the water pump went out.

I’m assuming there is air trapped somewhere in the cooling system. However, I can't seem to find where it's trapped. I'm hoping the description below might at least help someone point me to where the blockage is, or possibly point to something else that's causing the problem.

Symptoms:
-Car starts out at a good temperature when starting cold, but after a few minutes it overheats
-Air blows out when I turn on the heater but no hot air
-Car runs fine when I turn it on. No rough running or extra exhaust so I would tend to rule out any head gasket problems.
-I can hear the heater core motor running.
-Just before it's about to overheat, the radiator jerks around a bit like it's super hot. The upper radiator hose is boiling hot. The other hose going to the thermostat is cold (which I suspect is normal since the radiator would cool the water on its way down?)
-Both heater hoses are warm, but definitely not hot like the upper radiator hose is. The heater hoses don't feel like they have much coolant running through them.
-Occasionally while the car is idling the RPM gauge jumps up and down from 1000 to 2000. This does not occur when I have the flush n fill cap removed.
-If I take the cap off the flush n fill kit in the heater inlet house I see no coolant. If I run the car for a few minutes and it reaches operating
temperature, some fluid sprays out periodically, but the interesting thing is is the temperature remains down. If I just keep adding fluid to the overflow tank, and let it shoot out the heater hose, the temperature stays down. If I cap off the heater hose again, after about a minute the car starts to overheat. Is this because the hot coolant can't get pass the heater core? This makes me think that the heater core may be plugged.

Actions take so far (all with heater turned on to max and blower on max):
-Replaced the water pump, pulley and belts
-Bled the cooling system 3 separate times following shop manual instructions (finally found the bleeder bolt and made sure it was open while bleeding).
-Took the water pump back off to inspect. Water pump looks fine and spins freely. Looked for any blockage in cooling hoses near water pump and found nothing blocking
-Changed the thermostat, making sure to install it in the correct direction.
-Replaced radiator cap
-Tried cracking open the flush n fill cap just a little but that still causes it to overheat.
-Flushed cooling system with thermostat removed and using one of those flush kits that attaches to the heater hose.
-Tried temporarily removing thermostat, no change
-Turned on A/C and the two radiator fans kicked in. When I run the heater on hot the two radiator fans only turn on if I've opened the flush n fill cap and let a lot of hot coolant escape for several minutes.

Questions:
-Could it be a clogged or bad radiator or heater core?
-What would you recommend I try next? I thought about disconnecting both heater hoses from the engine side and running the garden hose through one to see if it comes out the other end (should tell me if heater core is plugged?). Would attaching the garden hose also potentially clear the blockage?
-If this sounds like it could be a radiator problem, anything I could check on the radiator?

It all worked fine before the water pump? What was the pump's original problem and did it do a nasty overheat?

Did flushing show any or much junk coming out?

Sure seems like air is still in the system either not purged out or gasses entering thru a blown gasket. Check pressure at pressure cap for pressuring up way too quickly upon a cold start up.

Heater not warm suggest air or it's blocked. Is this "flush kit" possibly the problem if left in a hose?

T
Tom Greenleaf - MetroWest Boston - USA
_________________________________________

http://www.autoacsystems.com/tomgreenleaf/

In Reply To

(This post was edited by jcollins23 on Jun 19, 2008, 11:50 AM)

Cap can be tested by the pressure testing kits that I think you can rent now at places like AutoZone - I don't think that's the issue at all. If you can feel any pressure in a hose from when cap was off the cap probably is working pressure release wise.

Still think you have air to get out. The flushing being clean is a good sign. Air can be a nightmare with some cars. When you fill it best you can thru cap if on radiator, highest hose if need be, open any bleeder if the high point till coolant comes out you would think it would be close enough but you are saying heater doesn't work so obviously not.

That is very likely vapor, air, but not liquid going thru the lines.

I said before if you notice it pressure up fast from cold that's too fast - hard to define that. Remove cap if known to hold pressure when warmer but BE WICKED CAREFUL ABOUT THAT!!!! and put it back on. If it pressures up again right away there's just combustion gasses likely getting into cooling system - that is usually caused by a gasket leak any that are sealing exhaust gasses or combustion gasses from cooling system. Usually a head gasket. It can be a tough call and usually you see bubbles or recovery tank fill right up time after time. Diag that well as it's a lot of work to be wrong there and this could still be a purging problem.

Some purging tricks are to get it as full as you can by all means. Warm it up just till you know thermostat is open. Shut down - it actually warms up a tad when first shut down and tilt the car such that the radiator cap or best fill spot is the highest within some sane angle. If that helps and it start to do better - heat works then it should finish itself by driving, stop and cool drive again, keep checking level at tank. At some point just the recovery tank shout get the air to tank and return only liquid and it's DONE!

T
Tom Greenleaf - MetroWest Boston - USA
_________________________________________

http://www.autoacsystems.com/tomgreenleaf/

Recheck the belt routing, we had a garage install it improperly.

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