I got a customers car here and it gets no heat unless you rev the motor.
I've already checked the blend doors and such and they are functioning fine.

The coolant is topped off. I've flushed the heater core and there are no signs of leaks anywere and there is no valve to the heater core.
The radiator is 2 weeks old.

Any idea's? I need to diagnose this issue by the end of the week.

 

Blower motor?

 

I'm definately no expert but I would say it is either a pinched or plugged hose or the water pump has eroded fins? That would sort of make sense why it would get more hot water pumping through the core when you rev it up.

 

Water Pump ? When I first bought my 01 XJ the heater did not work and while searching for a solution to my problem ( previous owner used stop leak which gummed up the t-stat ) a bunch of posts pointed to the water pump when it will only blow hot air when the engine is revving.

If the water pump is only holding on by a thread meaning that the fins are curroded and worn out or even possibly missing then it makes sense that revving the engine would make the pump work harder which means you will get some circulation through the heater core thus causing it to blow warm air.

 

Ok I forgot to mention, Blower motor works fine.
It runs at a perfect 210 degrees.
I flushed the core and water ran through it easily.
All the hoses are not pinched or colapsed.

Could it be thermostat over cooling? Idk right now I'm kinda burnt out from the busy day I had with mutiple vehicles.

 

whoops... I think its a bad t stat I got a new one that was bad... stuck open

 

X2. Does the heater flush come out clean or is it rust colored water?

 

Today I'm taking it off and replacing it. Maybe a higher temp will work?
Came out so clean you could drink it lol


Well today looks like a slow day so I'll have more time to spend on it.
I gotta get this thing fixed cause this guy owns the garage we rent lol

 

Check the water pump, sounds like its missing vanes

 

if the temp gauge shows 210 I doubt the t-stat is bad, sounds like the water pump (as others said)

 

Found the problem.
Somebody globbed up the T-stat housing with RTV thus clogging the port on the T-stat housing to the heater hose going to the core.
Just to be safe I put a new T-stat and gasket on with no RTV and now it blows nice and hot.

 

LOL, someone figured 'if alittle is good, alot must be better'
Glad you got it sorted out.

 

Tell me about it
I had this one guy red rtv his entire intake on a old chevy 350 and I spent over an hour trying to get the dang thing off with out breaking it.
Some people get so happy with that stuff lol

 

glad you fixed it