Complete cooling system failure

[_HighVoltage_]

This happened today and It was rather spectacular.

It did not happen to the Volvo though, it happened in my friend's Mexican built Mk3 Golf. She stopped to buy something from the store and left the car running. She came back 2 minutes later, everything is still normal. As soon as she put it in gear and started backing out - big cloud of smoke from the hood.

I step out and see an enormous lake of coolant all over the place. It took me a couple of minutes before I got the hood open because everything was covered in the boiling hot brown fluid.

With the hood open, the problem was immediately apparent. The temperature sensor (which she replaced herself) had popped out and ALL the pressurized coolant had flown from there.

I went back to get my tools and my car. I thought - just buy coolant, fill it up, bleed it...end of story. But then her boyfriend, who is a VW specialist, but he is not here right now told her that under no circumstances should we fill with new coolant, unless we had completely drained out the radiator (disconnect the lower hose).

What is the reasoning behind that? Also, why does it have to be filled with this specific type of fluid? Can we not just use the green PEAK stuff that says it's universal?

Meanwhile, we put some water in the system and nursed the car back home (less than 1 mile).

 

[EyeMWing]

It needs to be filled with a special fluid because it's Specially Engineered (actually, it's the same shit with some food coloring and a hefty profit margin).

As for needing to drain the radiator, probably just some paranoid bullshit.

 

[boganbusman]

If it had some "special" VW coolant then he probably just wanted to prevent you from mixing it with regular coolant. Different types of coolant shouldn't mixed (like red + green).

However if the coolant was BROWN then rust has already taken over and it doesn't matter what you put in there. Filling it with water was the right thing to do though.

 

[_HighVoltage_]

Well, when I say brown...this is the color of the "special" VW coolant. But why shouldn't they be mixed?

My Volvo also says to use only Volvo Coolant, but I've been using the green PEAK stuff with no problems whatsoever.

 

[boganbusman]

Different coolants are based on different combinations of chemicals. Putting two together that don't match can create an unwanted chemical reaction, like turning it into thick yucky gel or rapidly advancing electrolysis/corrosion, etc.
You might get away with mixing two types but that would be pure luck. Not worth the risk IMO

As for the Volvo, if you're only using one type of coolant then that's fine. Just don't try mixing the Volvo stuff and PEAK together unless you know for sure that they are compatible.

 

[Dr_Grip]

Well, when I say brown...this is the color of the "special" VW coolant.

Special VW coolant should be blue.
As for draining the system completely: I would not say it's necessary, but i'd use a massive oil leak to change the oil while at it, too.

EDIT: Did some research on VW coolant. It's blue (G11) for cast iron engine blocks and red (G12) for aluminium ones. These two should never be mixed, but there's a lavender/pink (G12 Plus aka G12 Plus Plus aka G12 Supra) coolant that can be mixed with both and has since (around 2005) replaced both blue and red.
If you mix blue and red, it'll create a brown jelly that will have to be washed out of the system, so don't do it.

 

[_HighVoltage_]

Okay, drained the coolant today. I insisted on flushing the system, but she didn't want to...so there would still be some of the old pink fluid inside. Filled up with Prestone green coolant, and we are bleeding the system now. (yet another thing I'm not a big fan of. I read somewhere that VW engines specifically bleed themselves of air pockets, as you drive along.)

 

[GRtak]

Most engine bleed themselves of air pockets(that is part of the reason for the expansion/overflow tank). Some are better than others at doing it, but you should still do an intial bleed to get the mass of air out.

 

[boganbusman]

Most engine bleed themselves of air pockets(that is part of the reason for the expansion/overflow tank).

Not quite. Most cars with pressurised coolant reservoirs can bleed themselves, but a regular overflow tank can't really do it that well.

 

[GRtak]

That is part of the function of the overflow tank. Hot water/ air bubbles are pushed into the bottom of the tank. When it cools down the fluid is sucked backed in, and since it draws from near the bottom of the tank, no air is drawn back into the radiator. It is not meant to completely purge the system, it just lets the little bit left find it's way out.

 

[M_Bolc]

If it was brown it was already mixed with green coolant, and from my previous experience with an MK3 that's a HUGE no-no. VW coolant is Cherry Red when used properly (or blue if its an older VW).

AFAIK the little round tank takes care of air bubbles in VWs, if you want to be sure start the car COLD without the lid on and let it idle for like 2-3 minutes, then screw it back on.

Oh, and many VW experts insist on using G11 or G12 as specified for the car since there are problems with rusting away the head gasket. The new G12+ works for any VW engine as said above.