JohnelP

what can go wrong

JAFO

<ul><li><a href="https://www.audiworld.com/tech/int5.shtml">https://www.audiworld.com/tech/int5.shtml</a</li></ul>

MonkeyMadness

Are the two hoses attached to the heater core hot? When you rev the engine do they both get harder (higher pressure)? You can take off the heater core outflow hose and see if anything is flowing through your heater core.

I had a similar problem and very little was flowing through the heater core. It was improved by back-flushing the heater core. There are many ways of doing this. The one that requires the least loss of coolant is to swap the two hoses going to the heater core. If there is serious crap in your heater core it will be pushed into your cooling system so this might not be the best option. I started by flushing my whole system with distilled water and then blew distilled water through the heater core. Some crap came out. Then I reconnected the core with the two hoses swapped. Then drained the system three times and put in new coolant. When I was done there was still crap in the system but a lot less. (Maybe I should have done it five times or drove for a day with just the distilled water.)

The heater now works great when the rpms are above 2k but is a little weak at idle.