Back working on the car - doing my head in already

[montez]

First off, how I have not been on in a year I do not know, Hello again everyone!

Previously I have rebuilt the head as my gasket had blown along with sorting out numerous other issues. Today I tried to take it to MOT and it is still cutting at around 2.5k rpm occasionally under light load.

On the way to the MOT the engine coolant (about 7 miles driving) high / coolant level low light came on and I panicked, I stopped the car and the engine felt hot and the coolant was luke warm. Gauge wise the temperature was 2.5 marks above 90 and has never reached above 3 marks.

I thought initially the thermostat may be sticking and the coolant was not circulating as the hose at the bottom of the rad was cool and the top was very hot. I undid the coolant cap and it was not under a huge amount of pressure but when I did this I stated to get a bit of bubbling at the block.

I checked the thermostat, and it seemed to be ok, topped up coolant and bled through on the heater matrix screw with an elevated expansion tank.

When I shut off the engine without the cap on coolant overflowed with bubbles which must have been in the system and you could feel some bubbles in the top rad pipe. The Rad does seem pretty hot at the top but cool at the bottom and no hot water appears to be getting to the expansion tank until i shut the engine off.

Does this sound normal? possible thermo sticking? Possible air lock?

Am i just been paranoid because since changing the MFTS the coolant temperature is shown higher?

This damn car, I just want to drive it.

[twoqu]

Can't realy help with the other description but from other members experience it does seem that using a 3 pin MFTS in place of the original 4 pin causes a higher gauge reading. If you have access to vag com you could check the first measuring block to verify what the actual temperature is, well at least what the ecu is seing!

[montez]

That's a good point ill plug it in and see if it is somewhere near calibration, oil is not getting high at all

[twoqu]

Heres the range of the blocks from another thread.

http://www.s2forum.com/forum/showpost.php?p=738661&postcount=6

[montez]

Ok here are my logs from vagcom, it looks like temperature is withing spec. What you think? Does anything else stand out for the engine cutting at low load, only fault it has registered is G28 intermittent and G28 no signal. I think this is the standard message for scanning without engine running

[twoqu]

The G28 intermittent might merit investigation. Could be insecure or have something on the tip of the sensor or the flywheel ring gear might be damaged. Guess you could remove the sensor block to check and if you have the patience of Jove, use a small brush to clean the ring gear. It would mean moving the engine round frequently to get to all the teeth mind!

[montez]

I had the g28 wire fail a couple of years ago so I spliced in and soldered a new one, I will check.

[twoqu]

Not questioning your skills but clearly its is suggesting a problem with the signal from the sensor to the ecu which of course could indicate the wiring. Worth a substitution for an undamaged one to, if nothing else, eliminate it.

[montez]

Yeah for sure, I had it running for about a year with no issue but having the head off and cable out it may have got stretched and damaged again. I have been looking for one but they don't appear easy to find, there is this http://www.ebay.co.uk/itm/Crankshaft...item46100341af but I cant work out if it is correct

[twoqu]

Says it fits RS2 so would think its ok. Would need to double check and cross reference the OE number. Not to sure about the quality but assuming you can get the old G28 out without much bother, it would be a quicker win perhaps!

[twoqu]

Some info from Dave here:

http://forums.quattroworld.com/s4s6/msgs/20986.phtml

Might need to watch the colour of the connector. I guess they might just be selling in effect a generic one with a black connector. As long as you mark the one you have changed shouldn't be a problem. Looks the V6 used the same one according to the link!

Just noticed it says crankshaft rather than engine speed sensor. The function should be the same but as I said above the connector colour is different.

[twoqu]

BE CAREFUL!
Looks like the V6 one has a different P/N! I was only scanning the end of the p/n.
It might only be something like the length but thats not of much use if its too short for example!
Might as well try and source a correct one from a reputable supplier. Even a used one might solve you issue. (I have seen you wanted ad!).

[montez]

Cheers for that Euro Car Parts appear to do one for £55 which seems longer and with the grey connector

[Rusty]

Did you bleed the rad out or just the heater matrix? When hot, water flows in to the header tank from the rad, if it doesn't do this then something isn't quite right...

[montez]

The bleed screw is no longer in existence on the rad. After I ran the vagcom test both the upper and lower large rad pipes were warm and was all of the rad. Before only the top of the rad was hot and the bottom was cool as was the thermostat housing. It does not actually forcefully flow through though does it, it is only an expansion tank with it being fed by the small pipe on the rad top?