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How to bleed coolant system

4K views 10 replies 3 participants last post by  Fourbears 
#1 ·
After replacing the top radiator elbow, as it was broken, I am trying to find the best way of bleeding the coolant. There seem to be 2 ways either a vacuum bleed for which I don’t have the tools or allowing the engine to get warm with the expansion tank top off. I have tried the second method and the engine temperature is stable at 90° but the heater is coldish. I have raised the front of the car up so to try to encourage the air to find the highest point but I guess there must be a better method?
 
Discussion starter · #4 ·
I have always started the car, filled the radiator, turned the heat on high, fan on low, leave the radiator cap off and let the car run, as the air escapes, the water level goes down, top it off. Do this till you don't see anymore air bubbles coming out.
Perhaps i need to run it a bit longer but why have the fan on low? I know you have to have the heater valves open hence it needs to be on high but what difference does the fan make?
 
Discussion starter · #5 ·
Due to limited space in the engine bay, the highest engine point is usually the cylinder head which can be below the level of the coolant reservoir. V.W and other manufacturers recommend vacuum bleeding cooling systems and ABS brakes. This avoids the risk taken when an engine has to be run for the coolant around thermostats to be hot enough for them to open and get flow. The most important engine temperature sensor is fitted in the cylinder head and a secondary sensor near the water pump usually drives gauges. Surrounded by air locks and water, the cylinder head may be partially filled and its temperature much higher than measured by the gauges. There are cheap vacuum bleed kits on Ebay, but most require an air line and make a lot of jet engine noise. I bought a cheap kit to use the adaptors with a small 12V vacuum pump.
Your solution is interesting. Can you post a photo of it set up or point me in the right direction?
 
Discussion starter · #7 ·
I’ve got the eezibleed kit which is simple to use but yes you do need low pressure. That vacuum kit looks good and I have been looking at them but that seems a good value kit. Just got to find a vacuum pump or compressor to use it. I doubt my tyre inflater would work!
 
Discussion starter · #8 ·
Well having left it overnight the level in the expansion tank had gone down which is good. So I topped it up and ran it and now have heat coming out of the heater! It gets a bitter hotter if I raise the revs so I may still have a tiny bit of air in it. Pleased so far!
 
Discussion starter · #10 ·
Well today the expansion tank is at the max level where I left it and I get heat after a few minutes through the vents. So that seems a success. Just got to sort the slam panel, wing, bonnet, front bumper, headlight out and get them painted.
 
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