Audi A3 1.9TDi overheating Problem

[darkocean]

Hi
I'm new on the Forums,and have a problem with my 2000 A3 1.9Tdi.
The problem is when I am driving shortish distances the temp needle shoots up to 120 Deg then the warnings lights flash and beep.After a short period it dramatically drops down to 60 odd deg and then works its way back to 90 odd deg and stays there perfectly..
It is starting to do this more regularly now..I think it is the thermostat sticking maybe but am told there are 2 thermostats...?
Please help as I am worried I could be damaging the engine...:1zhelp:

[Crasher]

It could simply be a faulty coolant temperature sender which is on the side of the head above the gearbox and easy to change but only when the engine is cold, server scalding damager.

The other possibility is that the water pump is suffering from a loose impeller and this is a much more involved job as it means removing the cam belt. If it is the water pump, you could easily damage the engine.

I suggest you start with a fault code read on the engine and instruments to see what is stored. When it is hot, with the engine off, feel the lower radiator hose and see if it is as hot as the top one.

[darkocean]

Thanks for the response.:)
would there be codes stored even if the display unit says everything is ok, the warning light only beeps and flashes for that brief period before the gauge shoots back down.
Surely if the impeller of the water gauge is damaged when i am driving normally it would be affecting the reading as well.Over long distances the temp stays around 92 deg , is this a normal reading..?
Thanks Again

[Crasher]

The memory is non volatile; if the coolant temperature sender is faulty (extremely common) it is normally logged as a code, but not always.

If the temp stays stable over long distances, that suggests a failed cooling fan, do the fans come on?

[darkocean]

Yes they do, it is very wierd as it does not always happen.Yesterday i drove it and it was fine, today it did it twice, and i was forced to pull over as i was concerned about damage to the engine

[Crasher]

Have you checked the top and bottom hoses to see how there temperatures compare?

[darkocean]

Will try that tonight, but surely if the temp spikes quickly and then back to normal both pipes would be hot then

[Crasher]

The quick spike suggests coolant temp sender, the engine cannot heat/cool in fast spikes.

[darkocean]

mmm good point,but say the thermostat was sticking though would you not get that result if it suddenly fully opened. I felt the pipes and they were both hot, however it was under the condition when it was fine.It did not replicate the problem again last night, damm fustrating thing...:aargh4:
I am going to go with your idea and replace the sensor and see if it happens again..

[Crasher]

Thermostats can’t move that fast, their response is very slow. They tens to stick open or shut and not move, often they stick open which over cools the engine.

[darkocean]

That makes sense thanks for your help I will go and try it and let you know :)

[darkocean]

Makes sense thx, will let y ou know how it goes :)

[darkocean]

Hey I thought i would give you an update, well I replaced the Coolant sensor and it made no difference, it happened again about 2 days later. However it shot up to 120 deg and then stayed there for about 2 minutes, my wife was driving..
Anyway it then went back to 90 deg no problem.I took it to a Garage with a VAG diagnostic test and it passed 100 % no problem nothing logged.The mechanic seems to think it is a problem with the Dash board...?Does this sound right...?
As the problem has not reared its head again for a week...aaaaarrrggggghhh...

[nevo]

Whats the mileage and how longs the waterpump been on it?

[darkocean]

98000 miles and not sure about the waterpump, it came with a full audi service history with the Cambelt changed at 68500 miles, whether they replaced the waterpump is unknown to me. but surely the waterpump would work or not work...?

[kite]

The plastic impellor on the waerpumps are known to break,or the impellor loosens on the spindle.
Both these cause the waterpump to perform below par, not pump water fast enough
causing the overheating.

[darkocean]

In hindsite of this do you think it is advisable to replace the waterpump, as i guess there is no quick way to find this out..

[nevo]

As kite says the pump impeller parts company with the shaft and can in the early stages of failure work sometimes, then just skip along turning at a slower speed than the shafts turning, however to change its a full cambelt change so you need to be sure.You say it was at 120 degrees for two minutes the engine would be seriously hot then,pop open the bonnet and check the top hose.

[darkocean]

Cool will have to wait for it to do it again and then i will check on the hose.
Will let you know what i find thx

[darkocean]

Hi just an update on my issue with the 'Overheating'. I replaced the thermostat from Audi and now the car temp goes up slowely to about 90 deg and then works its way up very slowely to 95-97 deg on my guage and the fan has kicked in then and the top and bottem Rad pipe are very hot. Is this a normal temp for it to be at...? Or is there another underlying problem... Cheers

[Crasher]

In my experience, the gauge should never go over 90, even when the true temperature of the engine is 115…

[darkocean]

I found another thing out when the guage is at about 96 deg it blows cold air when it is idling, however when you accelerate to about 2000 rpm for about 5 secs it then gets hot perfectly, this sounds like the waterpump to me is this correct..?

[Crasher]

Water pump.

[darkocean]

cheers, going to get it replaced asap and the cambelt at the same time ...will keep you posted ...:)

[darkocean]

Hi there back with news, well replaced the waterpump (Original audi), and the cambelt at the same time, but it still blows cold air when it just idles and then hot air when you accelerate, and the temp guage climbs up to 93 then works its way up to 100 odd deg then stays there,then sometimes comes back down a little. But I did notice 2 things, one is that when I put the key car key in and put it to ignition point the temp guage goes straight to about 68 deg, and this is when it is freezing...?(and i did replace the temp sender). 2nd thing is that whenthe car is just running on say startup if you turn the heater on, the fans both turn on immediately,and then when you turn the heater off they stop...?
Very Strange... Any Ideas...?thx

[nevo]

sorry to hear your contiuing woes darkocean,I think the next step must be to get someone with vcds and check the actual coolant temp against the gauge,also are you sure the heater matrix is not air locked.

[darkocean]

How would you be able to test if it was air locked...? can you bleed airlocks out relatively easily.With the guage maybe i got another faulty temp sender..Thought it is about 12 quid gonna maybe try another one, man i thought i had it sorted for awhile...:(

[nevo]

If the cars cold and you switch on the gauge should stay low till it warms up,I would always recommend a genuine vag temp sensor,I think firstly you need to check what the actual coolant temp is via vag.com as opposed to the gauge.was it a new water pump?

[darkocean]

Yes it was a brand new one from the audi dealership, cost 80 quid with a 40 quid part exchange for the old one. what is strange is that the sensor I bought was an orginal audi one as well, cost 16 quid..

[darkocean]

Sorry for being ignorant but what is vag.com...?

[nevo]

Vcds or vag.com as it used to be called is software that runs on a laptop to interrogate the car,the last temp sensor I bought from vw was £28,see if someone in your location has got it,you need to check the coolant temp,the sensor does two things, gauge and ECU,need to check the two values,the gauge could be faulty.

[darkocean]

Hey i got the software off the net(vcds-lite),and bought a cable.And monitored the temp while I was driving, the wierd thing is that the guage as soon as you turn the ignition on starts at about 70 odd deg, even when the software tells me it is about 43 deg. but then when i drive it around a bit it then kicks up to above 105 deg in the software and the guage says about 110-115. then i start getting worried and stopp the car. Could this still be a faulty sensor.?
I checked the Rad pipes and the top pipe is hot but the bottom one is cold,excuse my ignorance but surely the bottom pipe which is hooked up to the thermostat should not be cold , and which direction does the water flow, cause having the stat after the radiator does not make sense

[nevo]

The top hose is hot, the bottom cold ,thats normal,I would say you need a temp gauge,I believe vcds does read higher than the gauge,but with yours starting at 70 to me it looks shot.

[Crasher]

The sensor is a dual unit, if both the gauge and the dash are saying it is hot, the likelihood is that it IS hot and you should stop driving it and find out why. Don’t worry about the disparity of the readings, they all do that.

[darkocean]

Ok going to try a new sensor, and then back to square one..Its strange i felt the top pipe today when it said it was 100 odd deg and the top pipe was not that hot to touch, did not feel like a pipe at 100 deg.Anyway thanks for the feedback guys you have been really helpful :)