Coolant: Pentosin Pentofrost or Audi G12?

[Charles.waite]

Hey fellas, quick question. My car has the dreaded rear flange leak and I checked my coolant yesterday and it was below the minimum. I am going to swap out the flange soon, but I obviously want to top off the coolant. Can I mix Pentosin with the Audi G12 thats in there? The shop near me carries it CLICK and its the same stuff ECS and others sell. Otherwise I can get OEM from the dealer nearby.

Also is Pentosin decent? Or should I stick with the Audi G12?

One more question while I'm asking. Anything else I need to replace while I'm in there? I have a green temp sensor and I'm not having any issues with temps at all, but the sensor is pretty much coated with coolant. Should I buy a whole new sensor or just a new o-ring? I'd rather not have to take shit apart again to replace the sensor down the line if I can avoid it. Is THIS the correct O-Ring for the temp sensor?

[EBG 18T]

Pentosin is fine. I am running it right now.

[walky_talky20]

Yes, Pentosin is fine. Pentosin is in fact the OEM supplier for Audi G12. Same stuff, different bottle (and price).

Yes, that is the o-ring you need but the sensor is cheap and they do fail once in a while. I have actually seen them leak coolant right through the sensor itself (not the o-ring), so it's probably a good idea to put a fresh sensor in.

[old guy]

The sensor is cheap. Go ahead and replace it while you have everything apart.

[Charles.waite]

I need to drain the system before I tackle the flange right? The DIY says nothing about this and looking at b5 and b7 diys, they both state you should.

I was thinking of just pulling the sensor at the bottom drivers side near the radiator and letting it drain into a bucket then putting it back in once i'm done. any problems with this?

[old guy]

No problems with that. You do not need to totally drain all the coolant. All you need to do is to drain it below the level of the rear flange. The lower sensor is a pretty easy place to do it. If you look really close at the housing for the lower coolant sensor you may find a petcock valve that can be used to drain the coolant. I wasn’t aware that I had one until the last time I drained my coolant and I just happened to see it. I tried to turn it and it was extremely tight so I just stuck with pulling the sensor. You can give yours a try but if it doesn’t turn easily I would recommend just pulling the sensor. I can envision breaking the plastic petcock valve and then you would have to replace the complete hose assembly. Be sure to look for the “O” ring when you pull the sensor because it tends to stick in the housing.

Have fun!

[Charles.waite]

Cool, thanks for the tips. I just topped off with distilled water for now so I'll be fine until I can order the whole shebang (flange, sensor, o-rings, clip). You're right, I might as well go all new while I'm in there. I'll be sure to post pics of the bruises and cuts, I know its going to be a blast...

[nofearhawk]

Wait, its ok to mix?

Pentafrost sf only right? The one without silicates.

[Charles.waite]

Wait, its ok to mix?

Pentafrost sf only right? The one without silicates.

I think that's what they were saying. I have the regular G12 in my car so Pentofrost SF is the non OEM equivalent. I wouldn't mix the G12 with a G12+.

[old guy]

I think that's what they were saying. I have the regular G12 in my car so Pentofrost SF is the non OEM equivalent. I wouldn't mix the G12 with a G12+.

Actually all the G12's are compatible. You can mix G12 with G12+ as well as G12++. I have been using the G12++ for the past few years.

[CrazyCal]

FYI Pentosin is now available at O'reilly Auto Parts. Only place in town other than the dealer where I live. They're starting to expand their euro selection. They even have the Pentosin oils available in-store. I'm gonna try em out next oil change.

[Charles.waite]

So a little update since I was reading something about coolant bubbles the other day. So I topped off my tank last week with distilled water. It was below Min so I topped it up to right in the dead center of the two, where the seam of the tank is. FYI I did this while the engine was warm. SO this morning I was curious and checked the tank and it was way above max. I opened the top and hear a rush of air and some bubbles come out. I think weird. I got my sandwich at the deli, drive the 1/2 mile the rest of the way to work park (at a roughly 15 degree nose down slant). I checked the coolant level and ovbiously you can't tell from the slant. I open the lid and the pressure release starts dumping coolant down all over my poor subframe.

I very clearly saw the level of the tank rise and a bubble or two came out. Does this mean I need to bleed the system? I'm fairly sure on the process: back the bleeder screw on the coolant rail above the IM, and just wait until it stops bubbling. My heat is decent, nothing I would have ever complained about though thinking about it, its not as hot as I would like. Possible there are some bubbles caught in the heater core? Should I just prepare myself to do a full flush when I replace my coolant flange? The coolant is quite new so I would just reuse it.

BTW THIS THREAD is what I was referring too. Old Guy, you're the man!

[alimo20]

just to share my dumb story here - this weekend i replaced the coolant flange and lost the o-ring. a 144, various sized o-ring container didn't have any that matched. I ended up paying $11 for an overnight o-ring from amazon. oh well.

[old guy]

just to share my dumb story here - this weekend i replaced the coolant flange and lost the o-ring. a 144, various sized o-ring container didn't have any that matched. I ended up paying $11 for an overnight o-ring from amazon. oh well.

Look at it this way.....You still saved at least $150→$200 and had the satisfaction of doing it yourself!

[diagnosticator]

I am convinced that the only reliable way to fill the cooling system is to allow a lot of time for coolant to slowly gravity fill and push all the air out through the uncapped expansion tank cap opening. This process takes about an hour or longer. Letting the system air purge overnight the best. I have always used this time method with top ups as needed, and have never had any air trapped in the cooling system after refilling. If the refill process is rushed, air will be trapped in the cooling system causing more problems as the cooling system heats up. If enough time is allowed for the system to gravity fill naturally from the tank, there is no way for air to be trapped in the cooling system.

[alimo20]

Look at it this way.....You still saved at least $150→$200 and had the satisfaction of doing it yourself!

this is true - i think i'm close to have fixed almost every system. i hope the b7 platform is similar enough.

I am convinced that the only reliable way to fill the cooling system is to allow a lot of time for coolant to slowly gravity fill and push all the air out through the uncapped expansion tank cap opening. This process takes about an hour or longer. Letting the system air purge overnight the best. I have always used this time method with top ups as needed, and have never had any air trapped in the cooling system after refilling. If the refill process is rushed, air will be trapped in the cooling system causing more problems as the cooling system heats up. If enough time is allowed for the system to gravity fill naturally from the tank, there is no way for air to be trapped in the cooling system.

the only issue i have with this is that any points that dip and rise may still have air trapped in there. also even though the expansion tank is the highest point i don't know if the hydrostatic pressure from the 1 gallon or so stored in the upper part of the system would be enough to get an air pocket out of the heater core, even over a long amount of time.

i think the best method is doing it over the course of few days and drives, topping off/checking levels/bleeding through the upper coolant pipe.

man i love working on this car, its changed from a chore to a hobby.

[MacFady]

+1 to Diagnosticators suggestion. I always recommend bleeding the air via the expansion tank method, it only involves one screw as well so no additional wrenching. A lot of threads I've read over the years regarding some aspect of residual air in the system involved bleeding from the hard line. The one and only time the coolant was changed on my car not by myself it was done via the hard line and when I picked up the car it had a large metric bolt inserted in place of the plastic bleed screw, which had predictably stripped. I've been dealing with a slow coolant seep through the screw ever since, no matter what I've tried to stop it. Plan on attempting a more "permanent" obstruction on the next coolant flush but hasn't happened yet, the seeping is truly miniscule.

[tegraphile]

Wait, its ok to mix?

Pentafrost sf only right? The one without silicates.

I just picked up some Pentofrost SF from Carquest. It's nice when they carry German car stuff. Taking a quick peak at the Pentosin coolant website, they recommend SF for Audi 1996-2005 and ++ for 2006 models and beyond. Thoughts?

http://www.pentosin.net/f_antifreeze.asp

Sent from my Nexus 6 using Audizine mobile app

[Charles.waite]

Well Audi has moved on to G13 now. Its backwards compatible with G12 and G12+ (however it probably shouldn't be mixed). The Pentosin equivalent to G13 is Pentofrost E.

Also, Im pretty amused at me having started this thread 5 years ago. I still have nightmares remembering how much fun I had replacing that rear flange...

[Spike00513]

Well Audi has moved on to G13 now. Its backwards compatible with G12 and G12+ (however it probably shouldn't be mixed). The Pentosin equivalent to G13 is Pentofrost E.

Also, Im pretty amused at me having started this thread 5 years ago. I still have nightmares remembering how much fun I had replacing that rear flange...

G13 is made in a more eco-friendly manner.

And new xenons are D3S Hg-free.

[BARRY]

was looking up coolant myself and came across this.