Deezil

couple things that are weird on my 99 4.7L

- idle, step on throttle to take off and you can hear the water rushing through the heater core, if the rpms are above 1500 you never hear it, but after idling for a few seconds, then step on the gas, itll do it for a couple seconds

water pump issue?

- it will get warm at idle also, if you rev it up so the coolant is flowing as stated above, itll cool down.

thoughts?

thermostat?

dave1123

I'd say it's a combination of air in the heater core and the thermostat opening too soon.

freegdr

Sounds like partiality plugged heater core pump sucks water out faster than clog will let it back in .

Bustedback

Check the coolant level and condition before you spend any money on parts.

bigbadon

Bingo!! Thermostat has nothing to do with heater. Water for heater circuit bypasses thermostat.

Deezil

so maybe my water pump is bad then, if it doesn't circulate it at idle.. I wiggled the pulley a little bit today, but it doesn't leak a drop.

bigbadon

If that were the case then your engine would overheat at idle. What does your coolant look like inside the radiator? Is your coolant look like mud?

JackJare9455

backflush that core and see how it flows

Deezil

It DOES get warmer at idle, like I stated in the first post, coolant looks like coolant, no mud.




Backflush? Hook the hoses up backwards?

JackJare9455

no no no lol

Do a quick Google search.. tons of write ups and videos will come up.. you will disconnect your hoses from the thermostat housing and pump inlet tube.. and flush water through them BACKWARDS to the normal flow...

the outlet is the 3/4 hose that connects to your thermostat housing.. so hook the water up to that hose and drain it through the 5/8's hose (inlet)

Deezil

Oh ok, haha, Ill give that a shot today. Might replace the waterpump too and check out the thermotat to see whats up with the getting hot at idle

dave1123

Okay, here's my opinion on what's going on. Yes, your heater core is probably partially plugged. The air you hear is for "negative pressure cavitation", that is due to the pressure drop of the pump sucking against the partial clog, the disolved air in the coolant separates as bubbles.

The hose from the thermostat housing is the hot water supply from the engine. The one from the heater to the water pump is the return line. Disconnect both from the engine and stick a garden hose into the one from the water pump to back flush the heater core. Do not use air pressure because it can blow the heater core apart!

The thermostat is opening too quickly and not closing enough to maintain the normal operating temp. When you stop and idle, the reduced flow allows the engine to heat up. Replace it.

Replace that water pump before the bearings get loose enough for the impeller to strike the pump case. If it's plastic, it will destroy itself.

These are just my recommendations and my opinions. Your decision to do what you want with this.