2.5 V6 No hot air in cabin.....

[S4_dan]

Hi guys,

What with the good weather I haven't had a need to turn the temp over 21c for a long time! However, yesterday It was cold so turned it up to 25c and even though my engine sits a 90 there was very little heat. Turned it to Hi and still the same, a very luke warm blast of air.

My temp gauge takes the same amount of time to build up to 90c. Coolant levels all good.

I didn't check the pipes going into the bulkhead as it was really hammering down with rain when I got home.

I think I already know the answer, but I'm praying that someone will tell me it's not the thermostat! I hear its a big job on the 2.5 v6 lump?!

Dan

 

[BakPak]

If the coolant temp reaches 90 then I would say the thermostat is ok. What about the actuator valve, it might be sticking just open if you know what I mean. I have heard that replacing the thermostat on the V6 is a fairly big job so hope it's not that mate.

 

[Mike B]

If the engine warms up quickly the stat is doing its job.Hope so cos its not easy to get at.More likely to be one of the flap motors behind the glovebox.Mine have played up cos they begin to stick as the grease inside hardens.Take the box of and watch as you alter the controls.There is lots on here about this

 

[S4_dan]

Well the pipes that go through the bulkhead are getting very hot so the thermostat is ok.

I'm hazarding a guess at the actuator. Maybe it's from when I installed my Dension unit. I wonder if I've trapped something. Will know more tomorrow evening once I've pulled the glove box out.

 

[BakPak]

Wiring maybe, just a knocked connection?

 

[S4_dan]

Right, removed the glove box and I have full movement on the red lever/actuator.

The bottom hose going into the bulk head gets hot. The top hose is warm.....unless revving the engine 3k rpm then it begins to warm up. The air in the cabin got slightly warmer. Return the engine to idle and the air cools down from the vents.

I'd thinking my matrix is blocked or partially blocked. I will remove the hoses at the weekend and blast through with water to see if any gunge comes out.

I'm assuming my water pump is ok as I dont have any overheating issues and the temp needle always sits at 90c and I do push her sometimes.

 

[BakPak]

With the glove box removed so you can see the actuator valve, try switching between cold and hot and look to see the if the lever operating the valve is moving through its full travel. Just a thought mate.

 

[BakPak]

Sorry, just realized you have checked that. Doh!

 

[S4_dan]

Ok, so I've removed the heater core pipes, flushed backwards until clean water ran through, then forwards untill clean water came through. There wasn't much gunk coming out. I also replaced the CTS whilst I was in there. I bought a genuine one at beginning of summer when I had some hot starting issues but never got round to swapping it.

Took the car for a drive....I'm getting much hotter air through but it still doesn't feel 100%. The temp gauge went a bit funny. It got to 90c whilst I was driving then once stopped it would drop about 1 mm. Enough to make it sit slightly under the 90 line. Set off and goes back to 90 straight away. Did this a couple of times then once I pulled up at home it stayed on 90.

The air temp drops inside once the car has sat idling for a few mins. So i'm wondering if there is an issue with the genuine water pump fitted last november?!

Anyone know how to test the water pump? I removed a pipe off top of the coolant tank once I'd parked up and there was a constant flow of water returning back to the tank.

 

[BakPak]

When on idle does the temp drop below 90 and if so how quickly?

 

[S4_dan]

The needle only move about 1mm max! Takes about a minute to move. The outside temp at the time was 10.5c according to the DIS.

 

[john777w]

I think the reason the temp drops on idle, is that the coolant fan will cut in when the temp rises, as there is no air flow through the radiator. I think if the pump was faulty you would have cooling issues. Check when the electric fan cuts in first, if it's coming in to soon, this could be lowering the heater matrix temp??

 

[Mike B]

Seems you have tried everything and it wont be the waterpump cos that would cause overheating.I have heard that if the matrix begins to clog no amount of flushing will restore it and its best to replace it.On mine you can feel the heat with your hand on the casing in the bottom centre of the bulkhead with the gbox off.Are all the motors moving behind the box .I think there s/b three

 

[S4_dan]

Electric fan isn't kicking in, only does when I've been towing for a long time then start reversing the caravan down the drive then the fan comes on for a minute or two.
My viscous fan does run constantly although it never sounds like an aircraft taking off like it used to on my old A6 2.5, So I think that should be ok?

Mike, yes all three motors are working fine, I had the glove box out the other day and checked all movement. Would of been easier to use VCDS to check the output of the motors. Hindsight hey.....
I will see how it performs when the much colder temps get here, I might look to replace the matrix then. Or try a full coolant flush?

 

[Turkster]

i'd be doing the coolant flush before the matrix job mate, the matrix is not a nice job to do,

 

[Turkster]

i forgot to add, ive heard of people running "Descaler" through the system to unblock the heater matrix, not too sure if it works or its true, anyone ?