Overheating Issue
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AudiWorld Newcomer
Joined: Apr 2018
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Overheating Issue
My 2000 A4 1.8 quattro overheats under load. It doesn't overheat at idle, and temp goes down if I release pressure in coolant expansion tank.
I've flushed the heater core and have heat.
Changed coolant flange and temp sensor
Had system flushed, pink coolant installed
Still overheating
Changed thermostat, installed all makes, all models antifreeze to top off
Change spark plugs, didn't see any off color
New water pump
Car runs smooth although periodic cold start misfire.
No excessive white smoke
Coolant loss only on overheat
Upper radiator hose gets hot, lower hose gets barely warm.
Is it possible there's still air in the system?
What's my next step?
I've flushed the heater core and have heat.
Changed coolant flange and temp sensor
Had system flushed, pink coolant installed
Still overheating
Changed thermostat, installed all makes, all models antifreeze to top off
Change spark plugs, didn't see any off color
New water pump
Car runs smooth although periodic cold start misfire.
No excessive white smoke
Coolant loss only on overheat
Upper radiator hose gets hot, lower hose gets barely warm.
Is it possible there's still air in the system?
What's my next step?
AudiWorld Senior Member
Joined: Oct 2003
Posts: 765
Likes: 0
Well, sounds like you have done most of what would be suspect, however the difference in the hose temperatures suggests that you are not circulating coolant though the radiator. The fact that you have heat would suggest the water pump is working (although it could be lazy, but since you changed it I'd think it was fine), and if changing the thermostat didn't alter the problem I think that it would be OK (although I have seen new ones be bad, you could try heating the old one in a pan of water just to make sure it works), so about the only thing I can think of is a plugged radiator. I would try flushing it as a next step (I wonder how it could have been missed if you had the system flushed, but you are running out of things that could be wrong, getting flow though the engine and not realizing there was no flow in the radiator could be one), if you use a clean bucket you can capture the new coolant and just put it back when done. Anyway, air tends to block the heater, I've not seen it block the cooling circuit.
AudiWorld Senior Member
Joined: Jan 2004
Posts: 1,417
Likes: 28
From: Ocean Isle Beach NC
Audis this age frequently have blocked radiators. Plus if it had the wrong coolant sometime in its life that could add to the likelihood of clogs or reduced flow. I would disconnect the radiator and run a hose through it. If it does not flow fast you may need a new one.
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