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My 1998 NB 2.0 blew a gasket on the cooling hose flange. I replaced the gasket and flange. Once I filled the vehicle coolant and "thought" I had properly bleed the system, It overheated. I noticed that the heater never blew hot air and the fans never kicked on. I replaced the thermostat, housing and gasket. I reached in with my fingers while the thermo was off and felt the pump impeller. I didn't notice anything broke and it wouldn't rotate so I'm hoping that means the pump is ok and functional. I also, tested the fan. Both ran with A/C on. I removed electrical connector from the cooling fan thermo switch and jumped it to activate the fans. Both worked properly.

I then flushed the coolant completely and refilled the system. No noticeable leaks. It seems like i'm bleeding the system completely. After I "think" I have bleed the system, I ran the car. It again overheated without the fans kicking on and no hot air coming from the heater vents.

I'm at wits end here. Perhaps there's still air trapped in the system. Are there tricks to properly bleed the system that I don't know about? Could it be the pump even though it felt fine? Could it be the tension in the drive belt? Any help would be amazing.
 

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Hey, check these things:

1. is there any coolant, going back into the coolant tank? There should be a stream of coolant going back into the tank and should increase, when revving the engine.
a. check the return like and see if there is any restriction, it won't "burp" the system, if it is clogged.

check out this video; to see what it should be like and testing for restrictions in the return line:

https://www.youtube.com/watch?v=thcwatH_BpI

2. get or borrow a vacuum based cooling system filler; the vw factory manual recommends this and I have found, it is the best way to eliminate all air pockets. The fact that you have no heat and the fans aren't kicking on; is a classic indicator of air in the system (fans aren't kicking on; probably, because the coolant isn't getting to the sensor). I use a tool; from uView called the "airlift"; it uses compressed air but works excellent!

Amazon; I think has the cheapest prices for uView:

https://www.google.com/search?q=uview+coolant+filling+tool&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb#channel=sb&q=uview+airlift&rls=org.mozilla:en-US:official
 

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Thank you for your reply. I will check those things now. If there isn't coolant returning to the tank, is that due to a clog only? could it be the pump as well?
 

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Ok, I checked the return line. No flow. Not even at high rpms. Like on the video, I blew on the return line. I blew till my eyeballs about popped out. Could not get air to go into that line. Per the video, if there was no fluid coming from return line and I could blow air into line and get the coolant level to rise, that indicates that my pump is bad. But because I couldn't get air to go into the coolant line, I'm assuming that means I've got a clog somewhere.

Is there a next logical step or should I just start pulling hoses and check for clogs? Without advise, I would just pick the hoses easies to reach (lol that's so funny on this bug!!!)
 

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So I pulled the hose of the back of the throttle body. That hose is clean but it definitely didn't have any of the coolant I recently put in. I put in a very weak mix after the flush to circulate it around and then I was going to drain and put in normal mix. The fluid in that hose wasn't the weak mix. I got a paperclip and worked it around inside the nipple of the throttle body. Reconnect and blew in the hose. No luck. I should also mention that when I flushed the system, I did a version of the Haynes repair manual suggestion. I disconnected the upper hose from the flange. Stuck the garden hose in the upper hose going into the radiator. I put another short hose in the flange to direct the return water. I flushed until the water from the short hose was clear. This water obviously didn't fully circulate through the system. One, because of the blockage but I'm wondering if any other hoses should have been disconnected and water run through them.

Any suggestions on finding and removing this blockage would be wonderful.
 

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First I would pull the return hose and see if there's any blockages in it; some of the engines have a plastic restrictor near the coolant tank inside the hose, the restrictor has really tiny holes and are easy to get clogged. Some people have had a problem where that hose is blocked and that way it won't let the cooling system burp.
Once you confirm; there is no clog in the hose; I would reinstall the hose. then vacuum fill the cooling system; this way you totally eliminate air in the cooling system. Then I would see if the fans come on, if you have warm air from the heater and whether or not the car will overheat; I would then again check the return hose coolant flow. If you are getting very little or no coolant flow from the return line and the car overheats; then I would go ahead and replace the water pump and timing belt. Check out the timing belt and water pump kits from blauparts.com; they have some of the best prices and bang for the buck solutions, out there.

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Discussion Starter #7
First I would pull the return hose and see if there's any blockages in it; some of the engines have a plastic restrictor near the coolant tank inside the hose, the restrictor has really tiny holes and are easy to get clogged. Some people have had a problem where that hose is blocked and that way it won't let the cooling system burp.
Once you confirm; there is no clog in the hose; I would reinstall the hose. then vacuum fill the cooling system; this way you totally eliminate air in the cooling system.
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I've pulled the return line off the reservoir and the line from the TB to the block to isolate the TB. I can blow easily thru the TB. I then attached the line back to the TB and removed the end at the block. Couldn't blow at all. I removed the hose flange at the block and still couldn't force air through. See attached photo:
1) end going to TB
2) end going into the block
3) coolant hose flange

So with the flange removed, shouldn't I easily be able to blow air into the block? Is it safe to assume my blockage is there in the head? Is this very bad news or the procedure the same no matter where the blockage is?

Thank you again for any response and help.
 

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Hmm, I was mainly talking about the return hose; that goes from the cooling pressure tank (reservoir) to the next connection. I've removed a hose on a 2.0L Jetta; but maybe it is routed differently on a New Beetle. The MAIN thing; is to remove the hoses, to see if there is any restrictions in the hoses. In the video; he blows into the hose, noting if there is any bubbles going into the reservoir and if the coolant rises in the reservoir (no blockage).

https://www.youtube.com/watch?v=thcwatH_BpI

I'm going to work on a New Beetle at the shop; later tonite, that has a 2.0L, so I can look that over. I would just follow; what he says in the video, if there doesn't seem to be any restrictions based upon what he does, I would say you are good to go. Pressure fill and then, see if it the fans work, heater works and if it overheats. Many times; a car with a water pump that is failing; will be OK during idle but if you go for a short drive, it will overheat. In that case; the waterpump is on its way out; spinning on the impeller or cracked impeller. If it does; I would pull the thermostat, check the waterpump and tear down, do a waterpump/timing belt job.

Here is a video; showing how the impellers break, spin and fail.

https://www.youtube.com/watch?v=H_7De5aU4dI

https://www.youtube.com/watch?v=YbzDJqPIUrA

https://www.youtube.com/watch?v=y1S5uSgJq5w
 

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overheating

hello there. I have the same issue on my friend's beetle. i believe thats the correct hose, i just poke the pipe on the cyl head with long screw driver to clean it, put it back then suck and blow air on the small hose at the coolant reserve tank to check for any blockade if you can blow and suck air means its ok... But the real problem on me is the bad water pump impeller. Its really hard to tell/check peaking at the thermo housing. i end up opening the pump and off course its broken. Did change the pump & timing belt & coolant. now the beetle (Cloud is his name) is back on the road... :D
 

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Last night I worked on the 2003 2.0l new beetle; I took the hose off and blew into it ; the coolest level did rise in the tank and bubbled, so that would be an easy test, to make sure everything is okay and not blocked.


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