ianjax

just a lil update ! i didnt have time to flush the radiator today but planning to do tomorrow BUT i put back the old temp sensor (original audi and replaced at first timing belt service by audi at 69k) and the car reacted TOTALLY diferent ... temperature went up but just a hair after the midle and with the AC on and NO HEATER on !!! i dunno is that's a good news or make me more confused !!! Marty ... i changed the reservoir and has no cracks and cap is new too but i have no o rings on my reservoir and didnt know i suppose to have o ring on the cap !

twentysevenlitres

No o-ring's on the reservoir.
Single o-ring on the bottom end of the central section of the pressure cap.

That central section of the cap is the pressure valve, the outer part of the cap is effectively an umbrella for the overflow to stop it making a mess


Sounds like it was the temp sensor then! Always buy genuine with those sorts of parts.

ianjax

A LIL UPDATE ... friday i put the old temp sensor on and yesterday did the radiator flush ! drove about 15 miles and car start to overheat a lil ( like a hair over 12 oclock line) on the end of the drive while i was on the traffic light but as soon i start moving temp went back ( it was raining and about 83 degrees) no AC on btw ... today i drove like 10 miles with the AC on and it is 95 degrees here... temperature started to go up after 5 miles and after i turned AC off temp went back on and stayed good till i got home ! SOOOOO, in general the flush yesterday definitely did A HUGE difference but i still missing something ! I did all the bleeding procedure after flush and the fans are working ! gonna check ac pressure tomorrow but maybe i should get another temp sensor ? any thoughts ? what else can i do ? not losing any coolant btw and put fresh g12 coolant after flushing, a lil lost about the 50/50 mixture not knowing what still on the sistem but i am sure still pretty close to that ... thanks !

thejulex

Log engine temps with VCDS/vag-com to see what ECU is seeing.

AudiQC

With all the "problems" i have been thru in the last year, i betting on a bad radiator.... I think that a radiator will loose its "heat exchange coefficient" with time and not able to cool down the coolant and the engine as well as it was doing so when new. My ar is 10 years old now with almost 200k miles. Everything is new or in good conditions in the front (water pump, thermostat, fan are working well, etc._) except the radiator. Last year when i flushed it, i noticed some sandy particules in the old coolant and it was not a nice color. Lately in a trip to NYC from Montreal QC towing a camping trailer ( 3500 lbs) at about 75 to 80oF ambiant temp and average speed of 55 mph i could not use my AC othewise it was overheating. Oil temp was higher than usual and was steadily between 130 and 135oC or 265 and 275oF. All the rest was working well but "hot". Next week I will have a new radiator......

AudiQC

I decided to give myself an other change to save my old radiator. This weekend i have fushed it according to the following procedure from Greg Treantos
http://allroadfaq.com/downloads/mods/audi_coolant.pdf
I follow it plus an extra Prestone Cleaner step. That step is just after the Greg flush step and consist of adding the Prestone cleaner stuff + distilled water and run the car on normal for 5 to 6 hour in traffic and/or highway than flush the stuff, rince 3-4 time (flush and refill) than after the final job of filling the radiator with the antifreeze in proper mix to get the proper winter protection ( -35oF or -45of)
I am now into that step. Tomorrow i will travel back and forth from Montreal to Ottawa ( family visit) and Monday i will do the last flushing.
I can say that the first flushing has already improve the performance of my rad. If the second flush /cleaning process is as good as the first flush i would have saved my rad ....For how long i don't know for sure but certainly for a year or two.
I will keep you posted on the results.

ianjax

sorry guys, been out of town and busy with work but since last update when i did the radiator flush car is acting a lot better and actually didnt overheat at all for couple day when was super hot around 95deg and driving with ac on but then start with a " slight " overheat ! today i drove with my matco scanner and that's what i got !
*drove approximately for 15 min 50mpg with temp on 214f
* after 15min when i slow down on traffic a bit temp went to 216f and gauge start to go right a lil bit
*temp went back to 214f moving on 40mph reaching 217f tops and gauge still a lil bit over half mark
*on traffic light temp went to 221f and still there while on traffic, start driving and went back to 216f
*temp went 225f while going to the intercoastal bridge which has a good 1/4 mile hill and went back to 216f right after i got off and reachs 221 when i was about to get home ! total 30/40 min driving with ac off ! is those temp normal ? gauge went 1/4 after half mark when reach the 225f... no leaks, right coolant and mix ! maybe its time to change my radiator also ? it was 85deg today here btw so not extra hot ! thanks again ...

AudiQC

What were the water temp and oil temp readings on the dashboard gauges during that exercice ??

ianjax

oil temp was a lil bellow 225f and coolant temp was right on the center till 214f and went almost to the next line when reach 225f but mostly a lil after the half !

AudiQC

Well ! if oil temp is around 225F which in mine (Canadian) is equivalent to approx 108C...it is very good. On the other hand water the gauge reading on the dashboard should not be over 90C or 195F. On highway at 70 to 75 mph steady for 15 min, if oil temp does not go over 235F and water temp stay in the same range that you already experience in your exercice......everything is allright except your water gauge readings. That gauge is off....!! check that gauge ...the problem must be there!!!