Pc Cooling Guide
Hadda Condino
This post has been compiled from the misc posts on here (mostly by Mr. cheesewire) and the tons of good info is in this PDF (I presume from the Bentley manual?) - =page18_cr but please note it's for the North American-spec AAA engines, not the rest-of-world ABV engines.
The coolant warning light is actually a level sensor (those 2 metal spikes in the header tank are what the plug is for and measure yes/no on coolant level). There is no over-temp warning other than the gauge going up/big cloud of steam coming out of the engine bay :lol:
The main fan control temp sender is screwed into the radiator. This is a 3-pin brass jobber and has 2 different pin layouts depending on if you have early/late VR. It looks like early ones are all 3 pins in a row, late ones are 3 pins in a triangle shape.
Normal ranges of temps vary hugely depending on how hot it is out, how hard you're driving and how long you've been sitting in traffic. Generally speaking, you don't want the oil to go much over 110. Up to 118 is probably ok, but not for the entire journey. The engine isn't really properly warmed up until the oil hits 80ish.
Coolant temperatures tend to fluctuate much more depending on speed and/or sitting in traffic. Again, generally speaking you want the temp gauge to read in the middle of the gauge (98 degrees) when you're cruising. If you're pushing along hard or sitting in traffic, it will usually creep up to just over 104 or so. Much over 110 is not good as the pressure really starts to build up in the system and it's a likely indication that your fans may not be working.
Although the coolant is primarily water it won't boil at 100 degrees, as it's a pressurised system, so it's not necessarily a bad thing. However, the pressure will obviously build up in the system over these temperatures and put extra strain on what may well be 15+yr old rubber.
If you do get a gush of steam out of the engine bay - pull over as quickly as you can and stop! If you run the engine with no coolant and/or too hot, you're in danger of blowing the head gasket and/or warping the head. Neither of which are fun to replace and certainly a much bigger ball-ache than a bit of rubber pipe!
If you think you've got problems, it's always worth checking that the dash readout is actually correct. New senders are only a few quid from VAG and worth swapping if they're the old, crusty originals. Then at least you know you're not chasing phantom faults. The older and crustier they get, the more insulated they are from the actual water and thus, the less accurate they are.
If you plug the car into VAG-COM, it will display the temp that the ECU is reading (i.e. from the blue sender) so you can compare that to the reading on the gauge that's coming from the yellow sender and see if you've got a mis-match. There is of course still the possibility that both senders are crusty and reading wrong... :lol:
In the rad sensor plug - red wire is stage 1, thin red/black is stage 2. The other wire is the common connection. Bridge each of the two wires in turn across the common wire and see if both speeds come on. If they do, good.
The controller stays on for 10 minutes after you switch the car off (regardless of temperature) and will maintain power to the aux water pump. Stage 1 and 2 fans will come on if needed (same temps as when the car is running).
The idea behind the after-run pump is too circulate the water round the heater matrix and rear of the block to prevent localised over heating. Thus, the aux water pump runs regardless, come rain, shine, snow, ice and even if the engine hasn't even run (ignition on, then off).
You can use the following procedure to find out if your yellow temp sender is the cause of no after-run or not. This does not necessarily prove that the yellow temp sender is working, but it will prove if the circuitry that it controls is working or not.
When the engine is cold, you want to keep as much heat in as possible to get it all warmed up. The standard VR thermostat opens at 80 degrees. When the thermostat opens, it allows water to flow through the radiator to provide additional cooling to try and keep the engine termperature to a reasonable level.
If the thermostat is jammed open (usual state of failure) then your engine will take ages to get up to temp and thus be running rich and using a lot of fuel. The engine doesn't switch over to it's normal running map until it reads 70 degrees on the coolant temperature.
Apparently, the fan controller units (the box of relays in front of the washer fluid bottle). There's a couple of diodes inside that can come unsoldered from the PCB, but can be reattached with some soldering action.
Always refill your coolant system with the bright pink (hurrah!) G12+ coolant. Older G11 and G12 coolants shouldn't be used and certainly not mixed together as they'll clag up the coolant system. If possible, flush out the coolant system with clean water from a hose before re-filling.
The VR coolant system capacity is about 9 litres and the concentrations you should use are on the label of the G12+ bottles. However, for UK use where the temperature doesn't really get down all that cold, 3 litres (2 bottles) of G12+ will suffice and just fill the rest with water.
You can get lower temperature thermostats and radiator fan switches. These are just parts from other VWs, so don't go paying silly prices for them. Personally, I'd avoid the lower-temp thermostats as they can make the engine run too cool. The VR6's cold running map doesn't switch off until 70 C water temp, so if your Neuspeed low sender is opening at 70 C instead of the normal 80 C, you may stay in cold running mode for a bit longer than usual...and the blue temp sender has quite a big influence on the overall fuelling ;-)
Don't forget the quality "wire up fan stage 3 to a dash switch" mod ;-) An hour with a bit of wire and a switch will do wonders for your summer traffic temps. You can bridge the red/black stage 2 wire and also the black stage 3 wires with a 2 way switch and manually start them in the car.
Lastly, Mr. Cheesewire has also discovered you only need one, yes ONE, 11" SPAL fan to keep the water at 95 deg constantly in traffic, even when it's 27 deg C outside, like it was last night when he was stuck on the A12 for an hour waiting for an accident to clear...
i had an S4 before the vr now on that a lot of forum members did an after run pump mod which left the fan on longer and kicked it in quicker it kept the water circulating more do you know if one of the sensors could be changed to do this mod to the vr as i hear the pump and fan after shut down but never for long , a lot of renault cars will leave there pumps and fans on low speed for uptp 10minutes i like this idea as engines after switch off can quite often stay very hot for a long time and sometimes increasing tempurature due to build up off heat in certain areas of the engine and no more cooling effect being implemented especially after a long run down the motorway or a hard drive .
My previous 2ltr 8v rado did that, as did my G60. My 93 Vr has never had the fans come on after engine has been switched off, even after giving it some beans before hand. Potential problem, or how it should be?
Course it is. It might not cool quite as well, but nowt major. It just cost you more to fill up. The G12+ is anti-freeze/anti-corrosion solution and hasn't got quite as good thermal absorption qualities as water, but there's not much in it.
The water temp was no higher then it should be running, no more then 110. The water pump was replaced in January, whilst the engine was out. The temperature is fine even when im pushing it. So as you've said, its not worth losing sleep over :) Just wasnt sure if it should come on after the engine was switched off. I guess ill see if the days stay hot.
I also discovered you only need one, yes ONE, 11" SPAL fan to keep the water at 95 deg constantly in traffic, even when it's 27 deg C outside, like it was last night when I was stuck on the A12 for an hour waiting for an accident to clear.
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If there's one trend that's completely taken off in custom water-cooling in the last few years, it's hardline tubing. Over the last six years it's gone from being the reserve of only experienced enthusiasts working with local plastic suppliers and plumbing parts to a mainstream option that's even suitable for the adventurous beginner. We now have more choice than ever in this particular field, so it seems fitting (heh) that we update a little to keep with the times. Our modding forum actually hosted one of the original tutorials for this, written by esteemed member and modder Dan 'B Negative' Harper in 2013, so let's have a look and see if much has changed since then.
Let's begin with a heavy hitter, the choice between which tubing varieties to go for. People fight over this preference all the time, but really it boils down to understanding the materials and knowing the shortcomings of each so you can make a more informed decision.
PETG (polyethylene terephthalate glycol-modified) and Acrylic are both good materials for water-cooling. Which is better, however, will often come down to personal preference and which of the above options you value more. PETG is often marketed as beginner-friendly, largely thanks to it being easier to heat and bend initially. It's also very simple to cut with basic tools and is very much shatter-resistant for all those times you swing a hammer at your PC components.
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