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Tomorrow should be the day it all gets put back together. Finally. Just a quick question on torque settings. On the 12v site it says that the camshafts should be done to 30nm + half a turn. With the locking tool I was sent some pdf pages in German that say 70nm. Which is the correct answer? I bought two new original audi camshaft sprocket bolts so I imagine if they are designed to stretch the 30 + 1/2 is correct? Also, what's the correct amount for the block coolant drain plug and the oil sump plug? I've had 3 machine screws just shear on me on removal so far so I'm rather nervous about the correct torque settings for refitting. Definitely don't want to strip the oil sump plug. Will probably just slowly increase the torque and see if it leaks.
Interestingly the Bentley has two specs..one is the 70Nm (52 ft lb) in the Audi A6-C4 Avant with an AFC engine and the other is the 30Nm and a 180 turn in the Audi Cabriolet with an AFC engine..the same engines.
The Bentley is okay..but you have to be careful with the torque numbers they use.
I use the 70Nm/52 ft lb with no additional twist which works fine (I think that is an updated spec from Audi). If you use a "clicker" torque wrench..click it three times. I think the new camshaft bolts may not be "stretch bolts".
The block drain bolt, according to Bentley, should be tightened to 20Nm (15 ft lb)..sounds about right. Put some Vaseline on the "O" ring prior to installing too.
Thanks Rusty. Will go with the 70NM. By click three times do you mean actually move the bolt on a tiny bit three times? Is this something to do with static friction and rechecking dynamic?
I have read somewhere that the oil sump plug should be done to 30NM but I'm reluctant to do it quite that tight. Is that what the Bentley manual lists as well?
The Bentley says 40Nm or 30 ft lb on the drain plug. Seems like a high number. I just snug up the drain plug myself.
When I say "click three times" my experience has been that that first click may be misleading..I click it once..relax..click it again..relax..and a final third click. Sometimes you will get an extra slight tightening on the bolt after the first click..probably the tension torque on the bolt is changing.
Thanks Rusty. Did up the sump bolt to 25nm and so far no leak so will see how it goes. The camshafts were done to 70 plus a couple of tiny wee bits more on 2nd and 3rd click. Found that the belt was slightly too tight and the waterpump making a noise so off again and finish it tomorrow. When I took the camshaft bolts off they seemed to come off awfully easy. A little bit disconcerting that but the sprockets were firmly on the conical shafts so I guess that's correct.
I had quite a bit of trouble bleeding the system. I couldn't get a socket bit on the bleeder next to the g62 sensor and my allen wrench just wasn't up to it so had to give up on that. The plastic bleeder on the heater matrix pipe unscrewed out fine but nothing came out of it. In the end I had to pull the hoses half off the heater matrix pipes until it frothed the air out of the system. Great tips on here about that and very glad to have read that or I wouldn't have known what to do.
Next job is my fans. Once I got them reinstalled I have to check out what's going on. They only come on for about 5 seconds at about 92C then switch off again. The car slowly rises to over 100C like that in queuing traffic which is one of the reasons I decided to do the thermostat in the first place. Maybe with the new thermostat things will be better and hoping for a better behaviour when I put them back tomorrow. 12v has a thing on testing the g62 which will be first on the list if they are still misbehaving.
Bleeding the cooling system is fiddly, the block will hold a pocket of air when you change the water pump/thermostat. I never fuss with the bleeder near the G62..it can strip out.
The bleeder on the coolant hose can strip out too. It helps to mark the closed position..then open it a count the turns..about two..with the engine cold and the bleeder open two turns..and the coolant tank at the max mark..put the coolant tank cap on and start the car..let it warm up. You should get some dribble and bubbles as the engine gets warm. When the cooling fans come on..close the bleeder.
The radiator cooling fans are not controlled by the G62 sensor. There is a fan switch in the radiator that controls the radiator fans.
Sounds like your problem is a poor connection on the radiator fan switch..bad fan switch or maybe a relay. I would bet you have a bad fan switch as it comes on for 5 seconds and quits.
I would install an new fan switch..you will lose coolant..so be prepared to bleed the cooling system again. If you move quickly removing the old switch and installing the new one your coolant lose will be minimal.
Concerning the thermostat..the way to look at the Audi cooling system is..the thermostat controls the operating minimum temp. The radiator fan switch controls the maxim operating coolant temp.
You thermostat (I presume you used a 87*C thermostat) and radiator fan thermoswitch should be more or less matched.
On my 2.8 12v Cabriolet I use a 87*C thermostat and a 85*C/93*C (first speed radiator fans come on at 85*C and the high speed fans come on at 93*C) radiator fan switch..normally you would want the radiator fan switch at a higher number (like 95*C/102*C fan switch with a 87*C thermostat) but the fan switch on my radiator is on the far cold side from the hot coolant coming into the radiator. By the time the cold side of the radiator is at 95*C and the fans come on..the engine operating temp is above 103*C.
With the 85*C/93*C radiator fan thermoswitch the the engine runs at about 93*C most of the time in traffic. If your Audi 80 has the same positioning of the radiator fan switch as mine, Consider using a part number 251959481K 85*C/93*C radiator fan switch.
Last edited by Rusty Spokes; 04-16-2016 at 07:35 PM.
Finally got my car back on the road. Firstly, a big thanks to rusty and crazy for the tips and patience answering all my questions. Without a manual I don't think I could have got this far without your help. Really a big thanks!
I have run the car and done a wee test drive in it. I sat it on the drive running at idle for half an hour from when the first fan started up and then took it for a drive. I found that the fans come on a little better than they did before(maybe cleaning out the rad or cleaning the electrical contacts on the plugs and the fan connectors?) but that the car still likes to hover around 96C on the dash which it didn't used to do before this cooling problem developed. I note that the car has two stages of fan speed and wonder if it might not be switching on the first stage at all? There seem to be more than one relay involved and although in the past I pulled out a relay that said it was for the fan, the fan still worked??? Maybe that was a defective first speed relay? Or maybe it never gets to second stage and it was the second stage one? I find the two relay boxes and maps really rather confusing.
Anyway, today I sat in the car running a lap timer on the clicks from the relay for on and off and it started with roughly 8 seconds on (at 92C) for 25 seconds off and finally stabilised after half an hour at around 16 seconds on to 21 seconds off whilst showing 96C on the dash. I then took it for a drive and it dropped to 82C and held steady whilst at a decent forward speed so that must be the thermostat minimum controlling temp as registered by my dash thermometer. Still no timing belt covers on or undertray so that might provide a little extra cooling than normal but I imagine it is minimal.
Rusty, I see from the part number you kindly gave me that it is quoted as 87-77 92-82. I presume these are the two switch on and off temps for the different fan speed controls? I'm not sure if I should try to find replacement fan relays first(less messy though possibly expensive?) or just go with a new radiator switch and see if that is the issue. Does your car run at 96C if you just leave it running on the drive? I seem to remember that my car always ran at a very stable 83-85C temperature whether it was in traffic or moving at speed so that 96 can't be right surely?
Anyway, thanks again for all the help you've been it's much appreciated.
If I bridge the pins on the radiator sensor switch will that give me a good test of the radiator fan relays? I'm guessing that the 3 pin connector that attaches to the sensor in the radiator is made up of a ground and two signal wires for the two different fan speed setting relays. Do you know if the radiator switch is just an on off type of resistance switch? ie either high or low resistance or is it a more complicated variable resistance type of thing? If I simply bridge the ground wire to position 1 or 2 will it send a control signal to the relays to run the fans and give me a good test of the relays and electrical system? Without an electrical diagram I don't want to just start shorting things out if that is not how the system works! But, if it is that simple then it should be possible to determine if my relays are working correctly just by bridging the connectors and find out if the fans will run at both speeds or not.
Just checked the web for spec on the gates thermostat I put in and it is definitely an 87c thermostat.
Thanks again for taking the time to answer my questions
If I simply bridge the ground wire to position 1 or 2 will it send a control signal to the relays to run the fans and give me a good test of the relays and electrical system?
Yep..easy test..once you ground the pin 1 or 2..it completes a circuit (rather than sending a signal) for the appropriate relay and the fan should kick in. The high speed fans will be very powerful and loud, like an airplane.
An 87*C thermostat STARTS to open at 87*..and will be fully open at about 94*C..so the engine temps should run somewhere inside that range going down the road..depending on how warm or cold it is outside. Once in traffic..the thermo fan switch for the radiator controls the temps.
I probably should re-state..the 96*C is in traffic, on a hot day. Going down the road..it runs cooler..depending on the outside temp.
Your 82*C is cooler than my car..could just be your thermostat..nothing to worry about..I used a Behr thermostat. They will behave differently.
The Audi coupes and cabs with FWD and a 2.6/2.8 tend to run pretty cool..my oil temps are always pretty low.
On my 2.8 Avant Quattro..being a heavier car..the oil temps get up there quickly and get to 120*C sometimes...and the engine cooling system is working much harder than my 2.8 FWD Cabriolet.
I measure the operating temp with the VCDS on a laptop..
Possibly it's running at 82*C on the freeway because of air cooling. I've still got the undertray and belt covers off and it's not exactly hot here in the UK yet.. Or maybe just the gauge in the dash is not that accurate. Don't have an oil temp gauge in mine so don't know what that is doing.
Will try the bridging of the sensor wires to test the relays for both speeds tomorrow and if both work fine without shutting down prematurely then I will buy the radiator switch you suggested.
I have never heard my fans come on at the loud high speed before so it will be a good diagnostic as to what's going on.
04-15-2016, 03:47 PM
But, if it is that simple then it should be possible to determine if my relays are working correctly just by bridging the connectors and find out if the fans will run at both speeds or not.