Electronic Thermostat problems - ALT 2.0 Petrol engine

[Saturbo]

I had originally posted this in the B5 section not realising the car I have is a B6!

I've been looking around the forum and gleaned some good info on symptoms of thermostat failure for this model, but this electronic thermostat on the ALT engine is giving me some strange symptoms.

I got the car last week from my brother in law who has had it from new and its got FASH. Two days later it throws a CEL and the temp needle doesn't move from the 50 mark. To be honest I'm not sure it moved before the CEL came on as I'd only driven it a few times.

This alone would tell me its a stuck open thermostat, but the electric fan just behind the radiator starts about 5 seconds after starting the engine and goes to full speed and stays on until the engine is turned off which I wouldn't expect as this normally only kicks in when either the AC is on or the engine is too hot in slow moving traffic.

Can anybody here confirm if this symptom of the electric fan starting and running all the time is related to the electronic thermostat failure? I also have DTC codes pulled from the can and it give 4 faults P0116, P0112 and a couple others and mentions G83 which I belive is by the radiator bottom hose and since the engine isn't getting to temp I think this is why its showing that code

My daily driver is an A8 at the moment but I was considering this A4 instead if I can get it running right

Great site by the way

[Saturbo]

Ok for other members with an ALT petrol engine here is what I've found.

The thermostat was indeed stuck open not allowing the engine to heat up to normal temp. Along with this issue the coolant sensor at the lower return hose from the radiator also went south and causes the electric fan to run at full speed almost from starting the engine. Note that this engine does not have the viscous coupled fan.
While I had the inlet manifold removed to change the thermostat I also replaced the coolant sensor on the rear of the block - only £6 delivered from ebay.

Only issue I found that I had not gleaned from trawling web forums is that the ALT cranckcase breather pipe runs up the block through the web of the inlet manifold and as soon as I touched it the plastic crumbled.

Called local ATP and they had new pipe in stock - common part to fail apparently! No way to run without it as this allows unmetered air to enter the throttle body causing over fuelling and random misfire code when on WOT.

Will fit the lower sensor this weekend and let you know if all is working again.

[RickT]

Hi,

When i had my ALT I had the same issues, replaced both coolant sensors, thermostat and also the breather pipe (which is not cheap!)

In the end, it still ran cold after 3 thermostats.. --

Rick

[Saturbo]

I'm hoping that was just bad batch of thermostats you had! I read over your thread a few times but didn't pick up on that one.

I bought this one from Eurocarparts as ATP didn't have any in stock locally and quoted 2 weeks, cost was about the same give take a few quid and it was OEM part that arrived, even in VAG box.

Still a bit too dark in the evening to work on the car so it'll have to wait until the weekend to fit the new breather and second temp sensor.

Would you happen to know if the breather can be fitted without removing the inlet manifold again? I was hoping to just slacken the bolts and lift it a bit to get the bulb part in and feed the pipe up through the web without taking all the pipes off again

[Saturbo]

OK so it runed out that I needed another coolant sensor at the radiator outlet so fitted that and was ok for about 5 miles and threw a MIL light again.

This time VCDS said crank position sensor so sent for one from ECP.

I fitted the new crankshaft position sensor (harder than it looked because of the position!) cleared the codes and fired it up - no lights.
Took it for short run to check it out and all is well. Done around 60miles now and running sweet. MPG average as gone up from 28 to 34-35 MPG
Well chuffed!

[jsingh85]

Hi,

I've got a 2003 2.4 Cabriolet. I'm trying to work out if this is the same probem i have. Basically, the temperature gauge doesn't rise consistently. What it does is, starting from 50 go up a bit, then drop to 50, then go up but higher than previous, then drop to 50 again and will keep doing so until it reaches running temperature. When it reaches running temperature, it may stay there or it may drop down to 50 for the rest of the journey.

I'm not a technical person so it's not something i'd be able to fix myself but at least if i get an idea of what it is i can request accordingly. My head suggests it's just a sensor somewhere but the fans sometimes kick in when the gauge drops to 50.

Any ideas?

Thanks in Advance.

[Saturbo]

More than likely to be a thermostat problem sticking and/or staying open. When the temp falls outside the range of the coolant sensors the fans kick in.

I'd replace the sensors while the thermostat is being replaced - the cost of replacing the coolant sensors isn't that much if you get them from fleabay or some other source.

Of course your garage may not want to fit parts you source yourself talk to them nicely and they just might ;)