Burping the cooling system

R

Rp23g7

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Hey everyone, 1994 Mk8, 4.6

I did a suspension conversion and the oil filter adaptor gasket on the car and finally drove it. NICE RIDE, but running hot.

I took the cap off and let it cool a bit, started again and got a few little burps, but it still runs hot, say 3/4 or a little more on the guage. it didnt over heat, is there a way to burp the system? Is that what the little cap with the quarter inch drive in it is for on that coolant line?
 
Fill the coolant bottle to the line first, with that crossover tube open by using that quarter inch cap, then replace the coolant bottle cap, and then fill the crossover tube and replace that cap. you might have to do this a couple times to get all the air out.
 
Rp23g7 said:
I took the cap off and let it cool a bit, started again and got a few little burps, but it still runs hot, say 3/4 or a little more on the guage. it didnt over heat, is there a way to burp the system? Is that what the little cap with the quarter inch drive in it is for on that coolant line?
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If I'm reading this correctly, you never took off the cap at the crossover tube? That is a common mistake.

The crossover tube is the highest point in the system and the place where you want to 'burp' or allow air out of the cooling system. It even helps more to elevate the front of the car.

My general rule is to never have both the coolant reservoir cap and the coolant crossover cap off at the same time. You are either topping off the coolant reservoir or removing air from the system - never both.

If it didn't overheat and just needs 'burped' I recommend the "cold fill" procedure. Starting with the car sitting level or the front end elevated, system cold (ambient temperature or just warm to the touch and no pressure), then check that the coolant reservoir level is up to the 'Cold Fill' line. If not, remove the coolant reservoir cap and fill to the line or slightly above and replace the cap. Then remove the cap at the coolant crossover tube and fill as needed. Replace the cap at the coolant crossover tube, start the car and allow to warm up. Normally the coolant level in the reservoir will rise at that point. If it drops, shut it down, allow to cool and repeat the process.

If everything appears normal, drive as needed but when parked, repeat the process - whether that's in a couple hours or preferably overnight. When the coolant reservoir does not require topping off and the coolant crossover is full when checked, you shouldn't have any air in the system and you should be good to go. It may take two, three or more times to get all the air out of the system.
 
Awsome info, I bought a aftermarket plug, since I didn't see a 20 yr old metal cooling system plug removal going well, and it didn't.

After spraying with PBBlaster and sitting overnight, I tried a quarter drive ratchet and adaptor, too tight, tried a 1/2 drive ratchet with adaptor, too tight.

Ok so shock it, 1/2 drive air gun with adaptor, broke the adaptor right off, tried another, same thing.

Vise grips, too tight

Ok air chisel, that worked, the threads were really corroded and I think the o ring was gone.
Filled it and ran it for 30 min, Gauge stayed right in the middle, drove it 10 miles or so, success.
 
Just wanted to chime in and say "Nice work." As you can see, you aren't the first to play this game, but you aced it on round 2. Way to think ahead with the new plug.

I'm glad you're fixed up and back on the road!
 
A few people make a stainless steel cross over cap with a large external hex so you can use a socket or box wrench. It is a must have modification.
 
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