I have a 2004 1.8T. Just put a new thermostat housing in. Car come up to temp fine and the temp gauge stays in the middle. I turn the heat up to high. When I am sitting a idle it does not blow real hot air but if I rev it up a few times it will blow hot air then eventually cool back down to luke warm air.

I did some searching and its looking more towards the heater core possibly being plugged up since the engine is not overheating.

Does anyone have any ideas or other things I can check before I go start replacing things?

Thanks

 

coolant is prob not full.

 

yea im dealing with the same thing right now , just flush the core to get the air/debris out and you should be fine , i would do the whole system flush but in a month or so imma need to do the timing service so whats the point.
good luck

 

coolant is full, havent done a system flush yet tho

it seems to be hit or miss

now it will blow really hot air after it warms up or when i am coasting it will start to blow cooler air, it is acting really weird, ill give it a few days and see what happens, mabye it does need flushed

 

Mine did the same thing after I replaced my thermostat. It was because of an air pocket in the system, and my flange getting worse.

 

would it be eaiser to just start the car with the cap off for the coolant and let it come up to temp or is there another way i should do it to get possible air out of the system

thanks

 

thats what they say to do, but it didnt work for me. may have had something to do with the flange leak. I had to put the cap back on, which caused the car to pull the coolant in from the reservoir.

You are supposed to be able to just let it run with the cap off, so I would try that first. Thats what i did, it just didnt work. When my mech. was trying to fill it after he did the TB he also ran it at around 3k for a while to try to get it to circulate faster.

 

Guys, I have the exact same problem with my 2002; hot air at high revs and cold at low revs. I did get the coolant low warning twice when it was extremely cold but both times the gauge went normal after 30 seconds of driving. Temp gause is steady as you indicated. My mechanic seems to think it's the impeller which used to be plastic and thereofre worn out. This means water pump and $$$. Any recommendation on flushing the system? I have seen some articles on it, seems messy but easy enough.

What have you guys found out so far? Did the flushing help?

Thanks.

 

Youre losing coolant so there is a leak somewhere, probably the flange, which also causes the system to not pressurize, which causes the heater not to work. This could be caused by any leak. Mine was also leaking from a cracked thermostat. The thermostat bolts onto the block under the IM, and you can see it from the top of the motor. Follow the hose that runs down off of the hard coolant pipe that runs across the top of the IM, it goes into the thermostat. Mine was all cracked at the top where that hose connects.

How many miles are on it? I did my TB and WP at 95k and the plastic impeller was just fine.

 

The car has 49,000 miles on it. My coolant reservoir is near max and I haven't seen any leaks in my driveway nor did the mechanic find any leaks. I checked all the hoses, no visible cracks. I guess it's not the thermostat beacuse the gauge works. I left the car running with the cap off, didn't do anything different except smoke escaped due to heat from the reservoir. At one point I did see coolant escaping from the bottom of the reservoir (it was closed), don't know if that's where the excess fluid gets expunged or do I have a leak?