b6,1.8t AVJ,5 SPEED MANUAL COOLANT/HEATER ISSUE

[fourringsrus]

Hi all, just picked up the above y reg January '01 b6 1.8 turbo 150.
The car is generally is cracking order with just a couple of tiny scratches etc which should vanish when properly polished and waxed.
The only niggle is that the temp gauge is only getting to around 65/70 and the heater is blowing cold.
When I collected the car 1 week ago the seller showed me bills etc for cam belt/water pump at around 25,000 miles and 2 years ago, so I felt that they are not imminent jobs.
He went on to explain that since he was given a newer car the Audi was parked for a couple of months and when he started it before Christmas the temp gauge was not rising to 90 at normal running temperature.
He was advised that he had a coolant temp sensor playing up so replaced it to no improvement, so went on to change the thermostat (£60 part)

This morning after a week of use and being bloody cold each day I decided to have a bit of a look about, so having read a few similar threads here on the forum this is the score so far;
Started car from cold and with coolant level checked and good
Allowed car to sit and idle for about 20 minutes
Altered heater controls in all positions, up/down, max cold to max hot etc and all flaps seem to be moving air about correctly
Gauge still at 70

Under bonnet
Top rad hose hot
Water pipes coming from what I think is the oil filter housing, hot
Bottom rad hose cold
Cant see hoses going to heater matrix, so don't know what they are doing.
Got the hump and thought I might nip up the village to my mates garage and see if he was able to shed any light on things or check anything for me.
Garage was closed, so turned around but noticed temp gauge climbing for the first time and assumed that there had been an air lock which I had cleared while squeezing hoses etc.
Got back onto my driveway and sat playing with the heater controls waiting for a sudden burst of heat to confirm my success.
The gauge started to drop back down to 70 and the air still cold.
Revved the engine to around 2.5/3000 rpm and heat started to come through the vents but turned cold immediately that I came off the throttle

Am I to think that the water pump is dud and just spinning on its shaft, and possibly replaced with a cheapo at the last occasion, or that the thermostat is a cheapo e-bay jobby, and that all he told is lies
I am thinking that I should ignore everything he said and start afresh from the beginning but I can't just throw money about pointlessly

Who has had this issue and what was the actual cure

January 2001
Audi A4 B6 1.8 TURBO 150 AVJ engine code , 5 speed manual with 91,000 miles
The car drives and runs superbly, if a little slow at starting from cold.
Many thanks in anticipation

Stuart

[kite]

It sounds like a failed stat to me.

I wish I could tpye...

[fourringsrus]

Yes it does but he said it was new, does £60 just for the part sound right, he said the stat comes in its' own housing.

Just being reading on Audizine, would a clogged matrix/core cause the temp gauge to play like this

[kite]

I think a failed waterpump would cause overheating.

I wish I could tpye...

[fourringsrus]

Yep, agreed and I think the stat does work and that I must a flow restriction. Reading some of Crashers' replies to similar threads the matrix clogging is common on this model so I'll have another look in the morning as I now know the location of the pipes is not where I had been looking and that they are a doddle to access
Thank you friend
Stuart

[fourringsrus]

Flushed my heater core with CLR. Lots of pics. (http://www.audizine.com/forum/showthread.php/464321-Flushed-my-heater-core-with-CLR-Lots-of-pics)

can anyone confirm which of the two pipes is the "in" and which is the "out", reading the link above with pictures I assume that the bottom hose is the "in" and the top is "out", can anyone confirm this ?

Thanks

Stuart

[fourringsrus]

Well, didn't get the matrix sorted or cleaned out yet but as there was not any water at the pipes anyway, I'm going for the thermostat and ignoring what the fibbing sod told me.
As I'm lead to understand that this engines' stat and apparently many others these days, comes in its' own housing would anybody on here have access to a diagram or picture of what this thing looks like and where it's positioned and whether I'll need any special tools or tricks to change it.
Obviously drain fluid swap unit refill fluid , but are there any little tricks to bleeding the system, ie; cold engine, hot engine, car upside down and back to front,.you get the picture.
Any pictures and tips gratefully received, and does £60 sound right, alternatively could it be just the old fashioned £10 thermostat like most old cars?

1.8 turbo AVJ, 5 speed manual in a B6, January 2001

Many thanks

Stuart

[Doctle Odd]

a4 b6 thermostat | eBay (http://www.ebay.ie/sch/i.html?_trksid=p3984.m570.l1313&_nkw=a4+b6+thermostat&_sacat=0&_from=R40)

[fourringsrus]

Thanks Doc, didn't see my one there, but they all look like normal stats , as opposed to what I expected

[Doctle Odd]

If you search with your engine size there should be plenty, genuine is always best! cheap easy fix tho

[fourringsrus]

Apparently not quite so cheap, spoke to Audi today, £66 comes within housing complete with temp sensor or sender, and is the only way to buy as it is an electronically controlled unit, still relatively simple though

[fourringsrus]

Bit of an update boys. Had a guy out to look at an issue on another car and asked his opinion on the issue with my car.
He is an Audi tech and plugged in some kind of code/fault reader device.
When my gauge said just under 70 c, his tool also showed the coolant as 68 c, so the gauge seems good.
Armed with the info so far he deduced that the water pump might be weak and might be either broken up or spinning on its' shaft once warm.
Thinking " in for a penny, in for a pound ", I might as well go for a cam belt kit and water pump as at least I would know those are done.
All done a couple of nights ago, but same issue persists.
Today, went to B&Q, bought 2 meters of correct bore clear hose and decided to flush and back flush the heater core/matrix, just to know that the "blockage" wasn't there.
IT WAS NOT , the matrix flowed clear and freely in both directions, with just the smallest amount of rusty coloured dusty sediment coming out.
The heater hoses are getting warm, the top rad hose warm, the bottom rad hose cold, the gauge at 70c and the heater only blowing warm or fairly hot when revving the engine at about 4000 rpm, but cold when the revs drop to tickover.
Am I to assume that it is definitely the stat, now that I know the water pump is good and the heater matrix is not restricting flow and that it seems to bleed well enough.
Thanks all

Stuart

[fourringsrus]

Update time, the cam belt and water pump renewed as above, I purchased the genuine thermostat from Audi at £66, which is a complete housing including stat and temp sender.
Had the part fitted yesterday, bled as normal, ie; via spout on rail across the top of the engine(front to back), test drive to get up to temperature.
While driving the car the heater seemed to be good but the gauge still only reaches 70c but when returning to low revs or tickover the heater is cold.
The rad top hose is super hot and hard but the bottom hose is still cold, tried to bleed off via heater hoses, plenty of steam etc but still big pressure at the expansion tank.

Is there some special trick way to the bleeding process with an ecu electronically controlled thermostat, ie vagcom to open it?
Is the pressure build up and apparent air lock being caused by something more sinister ie a slightly failing head gasket?

The car starts reasonably well, if a tad lazy and with a slight stutter initially which clears almost straight away.
The car exhausts show no steam.
She runs super smoothly and pulls really clean and strong through the gears.

Apart from the obvious reasons that I am starting to suspect the head gasket is failing, when I left the garage yesterday feeling quite naffed off , the mech suggested that if the h/gasket was on its' way out, that there are products on the market which in fluid form can be added to the coolant and actually repair the gasket while circulating.
As he described the product as metallic filling compound it dawned on me that when I flushed the heater matrix/core, all that came out in the flush was a copper coloured sandy sediment, so I'm thinking someone has tried this before.
Has the last owner tried the " sealer/repair " because he knew the h/gasket was dud or has he tried other things after not being able to bleed the car properly after he changed the thermostat ( which was full of crud and was clearly not a genuine part as all the part numbers had been scraped off the housing )

PLEASE HELP

Stuart

January 2001 1.8 t AVJ B6 a4

[fourringsrus]

Have been told that fuse 82 covers power to thermostat but can only find up to number 44 in the fuse panel at the drivers end of the dash.
Any ideas where the other fuses are located in the car.
Stuart

[fourringsrus]

Thanks crasher, looks like fun to access

[fourringsrus]

So it aint the fuse 82 then, any other ideas

[fourringsrus]

Anybody got any opinions or theories, I'm going round the twist with this one, do the coolant temp sensors tell the ecu to open the stat

[dan.taylor.1]

I would say if it's a leccy stat then fairly obviously something switch/sensor wise tells the stat to open, no doubt via the ecu. Reading your other post you've changed one, in the stat housing, but not the others? The one in the rad will usually only tell the fan controller when to kick the fan in. I can't see how a sensor fault would cause a cold heater issue, that's usually mechanical, so air lock, no circulation so waterpump as quite often the stat take off is before the stat so it gets heat quicker.

Have you bled the system, don't know if you know but if you undo the top hose clip and pull the hose back a bit there's a hole in the pipe off the rad to release air, or at least there is on my 2.5.

Dan

[fourringsrus]

Hello Dan , yes I know about the various bleeding techniques, thanks its just the same as yours.
The sensor in the stat is in fact not a sensor but a switch controlled by the ecu which picks up info via the coolant temp sensors , now if as you suggest, the unit at the rad only controls fans etc, would in your opinion, the sensor at the back of the head be telling the ecu to instruct the stat to open/close.
I am of the opinion after lots of reading via various Audi forum threads, that the air lock is being caused by the stat not opening and closing efficiently due to poor sinal being sent.
The heater matrix is a clear as a bell but does not receive a decent flow due to the above theory.
Maybe I need to have yet another go at bleeding or something else is creating an air lock. Water pump and cam belt also new and genuine as is the stat.

Stuart

[dan.taylor.1]

Yes the temp sensor on the head will tell the ecu the temp and the ecu will then tell the stat to open at the right time, god i hate leccy stats!

do you know if the heater matrix pipe comes off the head before or after the stat? if its before i cant see how the stat not opening correctly would make it blow cold, for instance, my 2.5 is permanently open but my heater is still hot after a short drive. if it was stuck shut it would be hot all the time.

Dan

[fourringsrus]

I believe the heater pipes are after the stat and therefore if the stat is not told to open, the coolant does not flow. the bottom rad hose is cold and implying no flow, thus no coolant to the matrix,............ I think.

Stuart

[dan.taylor.1]

In that case id be inclined, for the price of them (~£15 from tps?!) to change the temp sensor, and see what happens.

Dan

[fourringsrus]

Hi Dan and anyone else who is interested, I decided that my sensor theory was a good one so bought a new cylinder head unit this morning complete with new o-ring and clip £40 inc vat.The one I removed looked to be an e-bay special with no part numbers or manufacturers mark.
New one fitted, stat now opening, full coolant flow, gauge sits nice at 90c, very pleased.
Many thanks to all who offered opinions or advice

Stuart

[kite]

Well done Stu.

Sent from my GT-I9305 using Tapatalk 2

[dan.taylor.1]

Glad its sorted mate, amazing such a small sensor can **** everything up so much! shame they didn't program the ecu to use the other sensors as a backup system...!

Dan

[fourringsrus]

Absolutely right Dan.
Thanks boys.
I felt good this morning, so the old girl got knocked into shape with a clay bar, autoglym machine polished and maguires carnuba wax.
Looks just super now, but it looks like before I give the wife her cabby back, its' also going to get the shiney treatment in the morning, weather permitting.
I'll probably shoot some pictures up when they both look stunning, in the " what have you been doing to your car today thread"
Thanks again boys

Stuart

[Quiggs2001]

So what did you change? The engine coolant temperature switch?

[fourringsrus]

Yep, as said earlier in the thread somewhere, there is one in the bottom hose area which is in charge of fans/gauges and the other is on the rear end of the cylinder head.
Both coolant temp sensors must be good and reporting accurately to the ecu which in turn instructs the stupidly expensive thermostat to open/close

Stuart

[Quiggs2001]

So what did you change? The engine coolant temperature switch?

Well jaysus if this is one last step Im gonna take to get my heat working Im gonna go for it. Just flushed my matrix today with CLR I got from Amazon, no gunk at all. Water flowing freely through matrix.
Can you give me more details of the sensor from the head? Where did you get yours?
I only had my thermostat done a few weeks ago, so I know thats not the problem. System not airlocked either.

One important question, have you now got heat??

[fourringsrus]

The sensor and its price and part number is somewhere in the previous pages of this thread, I never had satisfactory heat unless revving the engine.I sold the car back in the Easter time this year.
Re the free flowing matrix, apparently the micro bore pipework will be by-passed and show free flow even if blocked, so maybe not safe to assume the matrix is good ( like I thought ).
Dont think I am being off with you but I sold the car and have probably forgotten most of what I did,BUT.... everything I did is in this thread somewhere, the sensor came from Audi and was not expensive, please do not buy an e-bay special, it aint worth it

[Quiggs2001]

Thanks so much for your replies pal. I appreciate you taking the time.

Im gonna order BOTH engine coolant temperature sensors I think. Just to make sure.
I had the Thermostat done a few weeks back, but I purchased a non-genuine one from my local motor factors. Thinking I should have just got genuine??

Spoke to Audi today, he said £22 odds for a genuine thermostat. Would that be the housing included you were speaking of?


Really at the end of my tether with this problem. I was having exact same issues as you, except my temp sits at 90 all the time (takes around 10 mins of driving or so to rise to that mind you)
I took car for a drive today and after wonderful heat blowing through the vents at high revs around 60 mph, then as soon as I stopped, cold air :(


Matrix has been flushed & backflushed (water flows through freely)
Checked for airlocks
Checked for leaks
Thermostat changed
New water pump

PS - I cant seem to find any part number, was it definitely this thread?

[Quiggs2001]

I never had satisfactory heat unless revving the engine.

But was this cured after changing the coolant temp sensor? Your heat worked well at idle too?

[fourringsrus]

No, I only got heat when holding the revs high.
The stat was around £70 including its' housing, as it was a totally electronically controlled unit which worked in conjunction with temp sensors and ecu etc. Having the good sender allowed an accurate gauge and thus accurate info being sent to the ecu and then onto the stat.

I just noticed in your signature that you appear to have 1.9 tdi, this thread is all about the rare 1.8 turbo petrol AVJ engine code, and will therefore have little in common with the diesel set up, however, if you stick with genuine senders and stat, the repeat your process thoroughly, you should be on a winner.

With reference to flush/backflush of the matrix, I am lead to believe by some of our guru members that you can do this until the cows come home, but if the microbore pipework within the unit are blocked, the water will bypass and give the impression of no obstruction and therefore you will possibly be looking for a new matrix.
I sold my car before getting to that stage, so cant really offer much more help.
Stick with genuine parts and only have to the job once,
Good luck fella

Stuart

[Quiggs2001]

Well heres hoping. Cars with mechanic as we speak. If this doesn't work, gona have to go with replacement of matrix.

Thanks so much for all the great advice dude. To Crasher also, hes been keeping me right via PM. Great forum!!

[Quiggs2001]

Quick update - Replacement of sensor was unfortunately not the solution of my problem :(

Looks like the matrix is coming out...

[fourringsrus]

Well at least with the b6, you wont need to remove the whole dash for access, unlike my b3/b4 cabby, which I am having to accept also has a dud matrix, good luck fella