How do you bleed out a sealed coolant system. - page 1 - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• How do you bleed out a sealed coolant system. by mtnsammy on 11 Apr, 2006 19:22
• Does anyone have any tips to filling the coolant system without bubbles. I know the overflow is supposed to burp out the bubbles, but I am having some serious overheating problems. When I drain the system I do not get much water out. I really think I have some air pockets.
  
  Has anyone tried the Flush n fill fittings from Prestone?? Which hoses would you install it on?
• #1 by sethyboy85 on 11 Apr, 2006 19:29
• make sure your thermostat is set in place correctly, it could be getting caught and not opening up all the way.
  
  I usually park on a hill and pop the cap off, let the car run for 5min fill up and go rev the piss out of it (while driving), then top off again if I had any bubbles I blew them through with 4k+ driving
• #2 by mtnsammy on 11 Apr, 2006 19:55
• I just found a thread on filling the system. It is on page 4 or 5. I think I am not getting all the air out. I'll list the suggestions below and update this tomorrow after trying these.
  
  1st the motor is in a Samurai, tooo cool.
  
  Point car up hill to allow air to gather in radiator.
  
  Remove top hose and fill till water comes out both hose and radiator.
  
  Check lower hose on block outlet for flow out of radiator to see if radiator is plugged.
  
  Run motor till heats up then check level again for bubbles.
  
  I did remove the thermostat and the motor overheated within 2 miles. Initially the motor was running great. I hit some stop and go then I started to overheat in traffic only. When it ran at highway speeds it was cool. Later it just overheated always.  I now think I may have spilt out too much coolant and devolped an air bubble that made it worse? We will see tomorrow with the new improved filling method.
• #3 by chrissev on 11 Apr, 2006 19:56
• Quote from: "mtnsammy"

  Does anyone have any tips to filling the coolant system without bubbles. I know the overflow is supposed to burp out the bubbles, but I am having some serious overheating problems. When I drain the system I do not get much water out. I really think I have some air pockets.
  
  Has anyone tried the Flush n fill fittings from Prestone?? Which hoses would you install it on?

  
  
  There is only one way to drain and fill the cooling system on a 1.5, 1.6 or 1.9 VW diesel, and this is it:  To drain:  remove the cap from the expansion tank.  Remove the bottom radiator hose from where it connects to the bottom of the waterpump, and allow the coolant to drain out of the radiator.  Remove the two bolts that hold the bottom spigot onto the waterpump, remove the spigot, and pull out the thermostat that is located in the waterpump.  The coolant will now drain out of the engine.  To refill:  Make sure everything disassembled is put back together again.  Remove the top hose from the radiator where it connects to the radiator.  Fill the cooling system with coolant through this hose (use a funnel).  When the coolant begins to spill out of the hose, quickly reconnect it to the top of the radiator, and top up the expansion tank.  Run the engine until it reaches normal operating temperature.  Turn it off and let it cool down.  When it is cooled, remove the cap from the expansion tank and let out any air that has accumulated.  The car at this point is ready to drive.  
  
  I read that your car only overheats in traffic?  This sounds like a problem with the cooling fan.  You might want to run the engine until it reaches normal operating temp then watch to see if the fan comes on.  If it doesn't, then you should check the thermo switch that is located in the base of the radiator on the right hand side, and also check the fan wiring to see if there is constant 12 volts to the wires (there should be).  The switch should be a closed circuit at I believe 220 degrees, and an open circuit below that.  Also clean it off if it is covered in cooling system sludge, this can act as an insulator and prevent the switch from reading the temp correctly.
  
  Good luck,
  
  Chris
• #4 by mtnsammy on 12 Apr, 2006 12:15
• I tried the fill procedure. After warm up I added only a little fluid. I let it run for about 1 hour then took it for a test run. I found it starting to warm up. I parked and idled again for 1/2 hour. Total time running now is 2 hours.
  
  I let the motor cool enough to open cap. I saw some bubbles??? I thought this was impossible since I just rebuilt the motor and still only have 200 miles on it. I pulled valve cover off and checked torque on head bolts. They were a little loose so I gave them another 90 degrees. I was supposed to get 1000 miles first but who am I to question this motor?
  
  The motor ran good for about 1/2 hour with no more bubbles. Now it overheats and bubbles again.
  
  I pray I do not have a blown head. I am getting very upset with this machine shop. It was bad enough they welded shut the oil port when they rebuilt the head. Now I wonder if they even knew how to weld the head?
  
  Just how many bubbles would show on a blown head?? is it normally a lot of large bubbles?
• #5 by mtnsammy on 12 Apr, 2006 14:27
• OK I have now redone everything too much. I need some more ideas from the crowd.
  
  Since the old days of playing with the TR3 I have never had to re torque heads so much.
  
  I am having overheating problems, duh. I am still on the breaking of a newly rebuilt motor. I have almost 200 miles on the motor. The ride to Petroworks was supposed to be a nice slow 60-65 MPH run. NOT  I am now plagued with overheating. At first I found a couple of leaks, then a large air bubble, then bubbles coming into the tank. I popped the valve cover off and checked the head bolts. WOW they seemed loose. Getting them to torque the first time( after the rebuild) was hard. The last 90 degrees today was very easy. Maybe because the motor was hot??? Initially when I started up the motor all was good. After 30 minutes I am seeing bubbles again.
  
  How many times do I need to re torque??
  
  Anyone ever just use a torque wrench and set the bolts to a set number??
  I believe there was less than 80 pounds torque to spin them another 90 degrees the last time today.
  This turn 90 degrees warm up another 90 degrees run 1000 miles and another 90. It doesn't seem right. Can I strip out the block?? can I overtorque the head??
• #6 by A Guy on 12 Apr, 2006 15:26
• Does you top rad hose have a small line moulded into it that feeds back to the over reservoir tank?  
  If you do and you have a vw rad there should be a line that's blocked of the top, passenger side of the rad.  If it's there here's what I just did.  I ran an extension line to a clean container.  Ran the car and kept filling the reservoir until it stayed level.  the air will escape from the added line to the container.  Then I put the cap on the reservoir and put a vise grip or any pliar on the extension line to stop the flow, remove extension, install plug back in and you should be good to go.  
  I've had a hell of a time over the last couple of months with bleeding my system then I thought of this and the system was good to go in minutes not hours .  Good luck.
• #7 by mtnsammy on 12 Apr, 2006 15:56
• No small hose. Lower hose to radiator. Upper hose to block which is shared by those down to pump and over tooil cooler/ reservior tank. I am thinking I may have a head bolt torque issue compounding the problem.
  
  If I am still not getting the air out, it may explain the temps but I think I have a mild head sealing issue. Any ideas on what torque numbers are reached on the final torque for the head bolts?
• #8 by chrissev on 13 Apr, 2006 12:16
• Quote from: "mtnsammy"

  OK I have now redone everything too much. I need some more ideas from the crowd.
  
  Since the old days of playing with the TR3 I have never had to re torque heads so much.
  
  I am having overheating problems, duh. I am still on the breaking of a newly rebuilt motor. I have almost 200 miles on the motor. The ride to Petroworks was supposed to be a nice slow 60-65 MPH run. NOT  I am now plagued with overheating. At first I found a couple of leaks, then a large air bubble, then bubbles coming into the tank. I popped the valve cover off and checked the head bolts. WOW they seemed loose. Getting them to torque the first time( after the rebuild) was hard. The last 90 degrees today was very easy. Maybe because the motor was hot??? Initially when I started up the motor all was good. After 30 minutes I am seeing bubbles again.
  
  How many times do I need to re torque??
  
  Anyone ever just use a torque wrench and set the bolts to a set number??
  I believe there was less than 80 pounds torque to spin them another 90 degrees the last time today.
  This turn 90 degrees warm up another 90 degrees run 1000 miles and another 90. It doesn't seem right. Can I strip out the block?? can I overtorque the head??

  
  
  Ok i can give you a couple of ideas for fixing your problem.  Firstly don't keep giving the head bolts 90 degree turns.  You'll end up either breaking a bolt or stripping the holes in the block.  First thing you might look at is there's a restrictor located in the big cooling hose that goes to the engine from the rad (top hose).  It sometimes gets clogged.  No idea why it is there.  I usually just take it out and throw it away (have done so on every diesel VW I've owned that had it) and I haven't had any problems.  So you might want to check that.  Second thing is sometimes for some unknown reason the impeller on the waterpump will move out about half an inch.  I have seen this on a couple of cars and it results in the symptoms that you are experiencing.  The impeller has to be in the right position or the coolant doesn't get pumped, then you get hot spots and boiling, leading to bubbles.  So you might want to check that.  The impeller should be right against the body of the pump.  Also, was the head checked for straightness?  Was the engine overheating before it was rebuilt?
• #9 by mtnsammy on 13 Apr, 2006 17:42
• chrissev
  I do not see any restrictors in the hose. It is an aftermarket hose custom fit to this install.
  
  The pump is new, but the impellar looks like it is placed proper. The clearances look the same as the old pump just alot cleaner.
  
  With out all the drama the motor was rebuilt due to a crooked deal on a used motor. The last break was when the idler pulley came out due to stripped threads causing 7 of 8 valves to bend and the cam broke in 5 places. I thought it best to start from scratch. Now I really don't know. I even had to drill out the oil port next to the head bolt. Very sloppy work. I did remeasure, retorque, and reinstall everything from the shop. An extra $100 at this point was no issue. That is why I am so confused. Everything measured well within spec. Head and block were perfectly flat.
  
  I still can not think of anything but the air bubbles or pocket. One more try tonight and tomorrow.  Kinda wierd is the upper hose gets warm, lower hose is cool, radiator is cool. I am thinking if not the airpockets it must be the pump. We'll see when I run it tonight.
• #10 by mtnsammy on 15 Apr, 2006 11:56
• Well I was looking for a clue and I found it. WHile feeling the radiator on the sensor side opposite of the hoses it was cool. The head temp gage said it was 280 and climbing. Fans running wild and then.................    
  POW
  The rear hose to the heater core blew off tearing the hose almost completely through.
  
  Now I will remove all hoses, flush fresh water thru all ports, and refill the system again. I am almost certain there is a plug somwhere and fear it is in the motor somewhere. we'll see tonight.
• #11 by chrissev on 16 Apr, 2006 10:22
• Quote from: "mtnsammy"

  Well I was looking for a clue and I found it. WHile feeling the radiator on the sensor side opposite of the hoses it was cool. The head temp gage said it was 280 and climbing. Fans running wild and then.................    
  POW
  The rear hose to the heater core blew off tearing the hose almost completely through.
  
  Now I will remove all hoses, flush fresh water thru all ports, and refill the system again. I am almost certain there is a plug somwhere and fear it is in the motor somewhere. we'll see tonight.

  
  
  did you verify that the thermostat opens when it is supposed to?  Sounds like for some reason the coolant isn't getting to the water pump.
• #12 by mtnsammy on 16 Apr, 2006 20:38
• Yes thermostat opens on time and was verified on stove with thermometer. I am still going thru the motor. With all the problems with the machine shop I no longer trust anything they did. I am flushing in both directions to see if there is some old gasket material floating around causing partial blocking.
• #13 by Katmandu on 22 Apr, 2006 05:48
• Quote from: mtnsammy

  Yes thermostat opens on time and was verified on stove with thermometer. I am still going thru the motor. With all the problems with the machine shop I no longer trust anything they did. I am flushing in both directions to see if there is some old gasket material floating around causing partial blocking.

  
   Annnnnndddd....
  
   Don't leave us in suspense!  :roll:  :shock:  :lol:
• #14 by mtnsammy on 24 Apr, 2006 18:45
• Not intended. I work graves alot. I start vacation in 4 days and will give considerable time to this project then. Right now it is parked in front of the hose. I will flush water into the pump blocking all other inputs and check for out flow of water. After I can ensure flow in the right direction I will back flush in the same manner. When I know the water will flow correctly I will replace bad hose, run for 1/2 hour and take to friends shop for combustion gas in coolant check. I assume it will work with a diesel the same as with a gas engine. I have pulled the head way too many times on this motor. I now own over 60 head bolts all used once. I am starting to think about going to no stretch studs with nuts and lock washers. I read somewhere the race motors are done this way. If I knew how to download pictures I would. I think you all would enjoy seeing this rig. It is not an extreme rock crawler but it has outdone all the locals, so far.