Any car mechanics out there

Hi All,
I have a 2004 Audi A4 and am having coolant system issues. I seem to be fo rever bleeding the system as air keeps getting stuck in the heater matrix ( so we have no heat) and more recently the temp gauge seems to be going up p ast normal for a bit and then goes back again. Also,the computer has start ed randomly saying it is low on coolant. I am assume both these symptoms a re because air happens to have got to the sensors.
There are 2 bleed points on it 1. a hole in one of the hoses which goes to the heater matrix 2. a nut on a metal water pipe on top of the engine which you undo a bit wh ich lets air out.
Based on my central heating experience ( :) ) I have brought the engine up to temp and then with the engine off (in case it sucks in air when bleedin g) I loosen the nut on top of the engine and let the air/ water and air mix come out until it is water only. I then do the same for the heater matrix .
Only other thing to say is that it seems to be losing water (needs topping up in the header tank) about once a week.
I can understand there may well be a leak somewhere but don't understand wh y it keeps getting air in the system.
Anyone have any ideas?
thanks
Lee.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Monday, 18 March 2019 19:14:02 UTC, snipped-for-privacy@yahoo.co.uk wrote:

forever bleeding the system as air keeps getting stuck in the heater matrix (so we have no heat) and more recently the temp gauge seems to be going up past normal for a bit and then goes back again. Also,the computer has sta rted randomly saying it is low on coolant. I am assume both these symptoms are because air happens to have got to the sensors.

which lets air out.

up to temp and then with the engine off (in case it sucks in air when bleed ing) I loosen the nut on top of the engine and let the air/ water and air m ix come out until it is water only. I then do the same for the heater matr ix.

g up in the header tank) about once a week.

why it keeps getting air in the system.

when water comes out what else is going to take its place? Just fix the lea k.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Fair point. Difficulty is I am struggling to find out where the leak is. It loses about 150ml over a week.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sorry replying to my own post have now woken up properly :) . In my situation, there is always plenty of water in the expansion tank so any water escaping should be topped up by that.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Blimey, this reminds me of my dads old Austin from the 1950s, I guess some things never change in cars. That was a pinn hole leak in the heater somewhere, but in those days you could simply change such bits. Brian
--
----- --
This newsgroup posting comes to you directly from...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You still can.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, 19 March 2019 06:29:45 UTC, snipped-for-privacy@yahoo.co.uk wrote:

If it's not externally leaking it can be head gasket failure or cracked cylinder head/block
Bubbles of exhaust gas force water out of overflow. Run engine with radiator cap off and see if there are exhaust gas bubbles coming out. Only do this when engine is cold.
Check oil filler cap does not have brown sludge adhering. (indicates water is getting into oil)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 18 Mar 2019 12:13:59 -0700 (PDT), snipped-for-privacy@yahoo.co.uk wrote:

If you are bleeding correctly it should be a one off operation, anything else and it could be early signs of head gasket failure.
Diagnosis is maybe beyond 'normal DIY'
Have the header tank 'sniffed' for combustion products https://www.sealey.co.uk/product/5637204645/combustion-leak-detector
Pressurise the coolant system and look for leaks https://www.sealey.co.uk/product/5637204624/cooling-system-tester-cap-system
Pressurise each cylinder and listen for leaks in an adjacent cylinder (easier with a petrol fuelled vehicle, just adapt a spark plug)
Do a leakdown test
https://en.wikipedia.org/wiki/Leak-down_tester
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, 19 March 2019 07:39:35 UTC, The Other Mike wrote:

forever bleeding the system as air keeps getting stuck in the heater matri x (so we have no heat) and more recently the temp gauge seems to be going u p past normal for a bit and then goes back again. Also,the computer has st arted randomly saying it is low on coolant. I am assume both these symptom s are because air happens to have got to the sensors.

which lets air out.

up to temp and then with the engine off (in case it sucks in air when blee ding) I loosen the nut on top of the engine and let the air/ water and air mix come out until it is water only. I then do the same for the heater mat rix.

ng up in the header tank) about once a week.

why it keeps getting air in the system.

tem

Maybe he works for Sealey.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 19 Mar 2019 12:51:24 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Nope, just the easiest to find, I'm sure there are other suppliers like Laser who sell the same bits of kit to the trade and Joe Bloggs.
Off the top of my head I think all I've ever bought from Sealey is a a hydraulic hub puller bought about 20 years ago.
This one:
https://www.sealey.co.uk/product/5637193693/hydraulic-hub-puller-set
Unlike the description it has failed to extract the most stubborn hubs.
My coolant pressure tester is a snap on one circa late 1980's and I have since manufactured my own adaptors for my more recent cars.
I built a leakdown tester some 20+ years ago.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, 19 March 2019 21:58:54 UTC, The Other Mike wrote:

I guess the point I semi-made is that those things you linked to cost a lot and would achieve little. OP already knows there's a leak. I'd start by trying the cheap easy approach, a bottle of leak seal. Sometimes it does. If not, you've got another job to do.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

But you can't safely poke around a running engine looking for a leak. Where a pressure tester comes in handy. Also useful when re-filling an engine cold. Allows you to bleed it more easily.
--
*7up is good for you, signed snow white*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wednesday, 20 March 2019 00:41:57 UTC, Dave Plowman (News) wrote:

no, you run it then look.

Last I checked you'd have to go back to the 1930s to find a car that didn't bleed its own coolant circuit.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 19 Mar 2019 18:48:34 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Time you checked again. Our relatively extensive petrol fuelled 'fleet' dates from the 1950's to the present day and all but two require bleeding when replacing the coolant. The exceptions being one dating from 1960, the other from 1972.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wednesday, 20 March 2019 11:47:23 UTC, The Other Mike wrote:

That's odd.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

As they say, you need to get out more.
On my last BMW, the heater wouldn't work at all if you'd drained and refilled the coolant, until you followed the bleed procedure with two bleed valves. Once the engine was hot and pressurized. Or you could do that cold with the help of a pressure tester...
--
*i souport publik edekashun.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 20/03/2019 13:39, Dave Plowman (News) wrote:

OK, so my car first went into production in the late 1980s - but it's got special tubes for bleeding. Comes of having the engine up the back and the rad up the front. I doubt it's the only mid-engined car with special bleed arrangements.
Andy
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
So update on my situation. The car is now overheating all the time and no a mount of revving helps. Looks like the thermostat is gone as top rad hose g ets very hot and the bottom cold. Have ordered one so hopefully it will arr ive tomorrow for fitting. Apparently there is an o ring sealing the plasti c housing to the block so I may be lucky and this was the source of the lea k too.
I was thinking I might as well replace th coolant and flush the rad with a hose. Is this a good idea? Also... Looks like I need to use some special st uff rather than good old water and antifreeze. Is this necessary? This will be a second car (about to buy a new one) that largely sits on the drive.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 22/03/2019 07:09, snipped-for-privacy@yahoo.co.uk wrote:

Water pump mate.
Need a water pump to make the water go that the thermostat stops.
If it is easily accessible simply remove te stat altogether to test..
? Have ordered one so

IF you have no circulation, the water in the cylinder head will boil and blow the pressure relilef system this losing coolant.
That is not a leak. It is protecting the hoses from rupturing

Cleaning out rads and replacing hoses is a good idea but PLEASE simply check that water pump.
IME they are slightly moire likely to go than a thermostat.
Once you have repaced that and te sta and te hoses and flushed the rad that's it. Cooling system 100% up to speed.
--
Of what good are dead warriors? … Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yeah will take a look whilst I am at it. I believe the water pump was changed a while ago but having said that I seem to remember it is plastic inside so anything could have happened. Ah well fun for the weekend.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.