Heating system problem

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iucle

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HI guys!
Yesterday noticed a heating problem with my A4 1.9tdi b7. Engine hot to 80ºC, barely warm air coming out of vents. On motorway, -2ºC outside, almost cold air from the vents. In city, hot air blowing but only if the vents are blowing slowly.
Opened the bonnet, looked the 2 hoses that go inside the firewall. One was hot, the other one, barely, almost cold.
Any suggestions?
Heating worked until now, cooling liquid at max level, apparently no leaks.

Thanks
 
It should get to 90 so that might mean the stat has failed.
 
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Thank you Mike,
Mine gets to 90 only when in congestion traffic, motorway or usual driving, never gets to 90ºC. In your opinion is that the thermostat?
Cheers!
 
Mike B said:
It should get to 90 so that might mean the stat has failed.
Click to expand...
Thank you Mike,
Mine gets to 90 only when in congestion traffic, motorway or usual driving, never gets to 90ºC. In your opinion is that the thermostat?
Cheers!
 
I had the same problem. A new heater matrix fixed it.
 
It should get to 90 and stay there thats what the stat is for.It could be the matrix as well if the pipes arent both the same but that might be helped by back flushing the system.I would also check the CTS but that needs diagnostics
 
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Think it was £70-£80 from euro car parts.
 
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Is th car isn't get to 90c then the thermostat is shot. Does it get to 90c and stay there?
 
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Dani_B19 said:
Is th car isn't get to 90c then the thermostat is shot. Does it get to 90c and stay there?
Click to expand...
It doesn't get to 90ºC, only when in bad congestion traffic. It stay lower than 90 all the time, like 75-80. Is the thermostat connected to the car heating as well? Or do I need changing the CTS as well or the heater matrix?

Cheers
 
Dani_B19 said:
Is th car isn't get to 90c then the thermostat is shot. Does it get to 90c and stay there?
Click to expand...
Plus when I checked the two pipes that go through the firewall, 1 is hot, the other one is cold-ish... Don't know if that's connected with the thermostat...
 
You could try a thermostat first, I Did but didn't change anything, there cheap less than a tenner and an hour or so to fit.
 
Don't be spending out on a heater matrix before checking cheaper options mate.

Have you scanned the car for fault codes? The cheapest and easiest option is the coolant temperature sensors, it's just over £30 for all the parts and is very easy to change yourself, if like me that doesn't fix the issue then change the thermostat, this is going to cost a little more, parts about £30 but unless your very good with removing cambelts then it's going to be about £100 labour, u reckon one of the above will solve your issue.

If it was the heater matrix the interior would stink and the car would be losing vast amounts of coolant.
 
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Dani_B19 said:
Don't be spending out on a heater matrix before checking cheaper options mate.

Have you scanned the car for fault codes? The cheapest and easiest option is the coolant temperature sensors, it's just over £30 for all the parts and is very easy to change yourself, if like me that doesn't fix the issue then change the thermostat, this is going to cost a little more, parts about £30 but unless your very good with removing cambelts then it's going to be about £100 labour, u reckon one of the above will solve your issue.

If it was the heater matrix the interior would stink and the car would be losing vast amounts of coolant.
Click to expand...

It wouldnt be losing coolent if the matrix is blocked.
 
If it was bust it would. But yes if it was blocked it wouldn't but why would it be blocked? There's nothing to block it to the severity he OP is talking about.
 
They block up over the yrs, as why people say to back flush them. Sometimes it works. He said that one of the pipes is cooler at the bulk head, which to me indicates a blockage/airlock. Mine was the same, when I removed the matrix very little fluid would go through the matrix.
 
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Dani_B19 said:
Don't be spending out on a heater matrix before checking cheaper options mate.

Have you scanned the car for fault codes? The cheapest and easiest option is the coolant temperature sensors, it's just over £30 for all the parts and is very easy to change yourself, if like me that doesn't fix the issue then change the thermostat, this is going to cost a little more, parts about £30 but unless your very good with removing cambelts then it's going to be about £100 labour, u reckon one of the above will solve your issue.

If it was the heater matrix the interior would stink and the car would be losing vast amounts of coolant.
Click to expand...
Cheers Dani, thanks a lot for your help.

1.) haven't scanned my car for codes as don't have vcds (have to get one some time)

2.) Not sure about the temperature sensor location.

Can be there? red arrow
Coolant


3.) I will also do the thermostat, just looked up a guide online (as the temperature fluctuates all the time and doesn't keep the 90ºC)
4.) I will do the matrix flush as well, so I can exclude it (i suspect that it can be clogged as the heat in the car went gradually from ok-ish to almost nothing).

So overall it looks like I have several problems.

Appreciate your help vey much!
 
francie said:
They block up over the yrs, as why people say to back flush them. Sometimes it works. He said that one of the pipes is cooler at the bulk head, which to me indicates a blockage/airlock. Mine was the same, when I removed the matrix very little fluid would go through the matrix.
Click to expand...
Thanks Francie, I will do the flush and see if it solves the problem (partially at least) as you say the bottom hose is not hot at all, so must be a blocked.
Thanks a lot for your help!
 
I took my heater matrix hoses filled the matrix with oven pride left for a hour then blasted out with the hose worked a treat
 
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audi upgrades
Yea mate but the OP also said the car isn't getting upto operating temperature also which doesn't necessarily mean the matrix is shot either.
 
As Dani has said above there maybe nothing wrong with the matrix.....

iucle said:
Engine hot to 80ºC, barely warm air coming out of vents. On motorway, -2ºC outside, almost cold air from the vents. In city, hot air blowing but only if the vents are blowing slowly.
Click to expand...

If the stat is goosed the engine will never get up to temperature as the stat isn't shut when it should be, to give the water time inside the block time heat up more. Therefore when driving in cold weather the water is cooling down again before it can get hot as it's circulating straight out of the block to the radiator and back again.....yet when you're in the city driving slowly the water isn't being circulated as fast through the system and has a little more time to get a little extra heat.

For the sake of about £4 for a new stat I would try that first instead of paying £70 - £80.
 
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carlcall said:
As Dani has said above there maybe nothing wrong with the matrix.....



If the stat is goosed the engine will never get up to temperature as the stat isn't shut when it should be, to give the water time inside the block time heat up more. Therefore when driving in cold weather the water is cooling down again before it can get hot as it's circulating straight out of the block to the radiator and back again.....yet when you're in the city driving slowly the water isn't being circulated as fast through the system and has a little more time to get a little extra heat.

For the sake of about £4 for a new stat I would try that first instead of paying £70 - £80.
Click to expand...


Thank you Carlcall looks like logic thinking :))
So you would exclude the CTS?

Cheers
 
Still say its likely to be the stat cos its a common cause of sudden loss of heat and the reason why it doesnt get to 90 .Dont look at the matrix first although it might benefit from a flush its very unlikely to suddenly block up .
 
Mike B said:
Still say its likely to be the stat cos its a common cause of sudden loss of heat and the reason why it doesnt get to 90 .Dont look at the matrix first although it might benefit from a flush its very unlikely to suddenly block up .
Click to expand...
Cheers!
Have the stat to collect at Eurocarparts today and will do the flush at the same time.
Do you know how much coolant will the lost in the process of changing the stat?

Thanks!
 
Maybe500mil if you are quick.Do the stat and check : the matrix maybe OK. I have never done mine and you will lose a lot of coolant if you do.Look at the old stat to see if its stuck open or anything jamming it open.ECP stats are rubbish get a genuine one
 
Mike B said:
Maybe500mil if you are quick.Do the stat and check : the matrix maybe OK. I have never done mine and you will lose a lot of coolant if you do.Look at the old stat to see if its stuck open or anything jamming it open
Click to expand...

Thanks! Didn't get a chance today as I was running all day left and right. Tomorrow after 11 I'm free so can do it. Have the thermostat already and the flush to back flush the matrix.
Btw, this morning at -4 it took ages to defrost the front windshield,actually didn't defrost it completely...
 
Yes mate, as people have said your better off getting one from Audi. Also is the one you have just the stat of the full stat housing?
 
Dani_B19 said:
Yes mate, as people have said your better off getting one from Audi. Also is the one you have just the stat of the full stat housing?
Click to expand...
I just bought the stat,without the housing.
Thought the housing should be fine if there is no leak in the system.
Would you recommend getting the housing as well?
Thanks!
 
Well looking at the genuine stat I have here I can't see how you'd take the old stat out and out the new one in mate. It's a full sealed housing.

Not saying you can't do it but not sure how you'd do it.
 
Dani_B19 said:
Well looking at the genuine stat I have here I can't see how you'd take the old stat out and out the new one in mate. It's a full sealed housing.

Not saying you can't do it but not sure how you'd do it.
Click to expand...
Do you have a picture by any chance?
 
Not to hand mate but can get one tomorrow morning.
 
Dani_B19 said:
Well looking at the genuine stat I have here I can't see how you'd take the old stat out and out the new one in mate. It's a full sealed housing.

Not saying you can't do it but not sure how you'd do it.
Click to expand...

Hey Dani,

Just had a talk with AUDI Cambridge.
The thermostat by itself would be £22+vat, the housing and seal are about £12, so overall about £40.
With Eurocarparts I go let a stat for £8 with the seal.
It's a little ripoff don't you think?
 
I've not done this job myself on the Audi, although I have changed stats on other vehicles to fix the problem you may be having. I believe the A4 stat is located in the housing by some small clips of some sort. These are known to break and can jam the stat open, so go canny. No doubt others more expert than I will give more specific advice.
 
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