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Discussion Starter #1 (Edited)
Facts: I just bought a 1999 New Beetle 2.0 L, 160K miles. This is my first volkswagen, I love it. I bought the car at an auction, and I have no history on it.

It had a coolant leak in the radiator and a busted fan that made a terrible noise when it kicked on, so I replaced the radaitor, the two fans, and the shroud around the radiator. It appears that the bug may have been in a minor front end collision because the fan was rubbing against the radiator.

I cranked it up and it runs fine, however, the coolant begans to boil over after the engine heats up. I do have to rev it up, to get the engine to heat up. The fans to kick on, but it stills seems to overheat.

So, check and fix the obvious. I replaced the water pump and the timing belt while I was and put it all back together making sure the timing was right. I had the thermostat removed and I used water only. None of the pink stuff.

Put it all back together, and it is still overheating. Now I am thinking it is a cracked head.

Other facts: oil not milkly, engine not missing, runs and sounds great, new water pump and new timing belt, the old water pump seemed to be OK, but with a little pressure and turning on the old water pump in my hands, the impeller literally crumbled in my hand. I have removed the thermostat.

I am now stumped. So, shall I pull the head and have it tested for a cracked head.

My thoughts that I need feedback on are : can a cracked head push air into the coolant causing the water pump to not move and cool the coolant efficiently?

I get sporadic pumping from the water line feeding the expansion tank. Oh yeah, I forgot to mention, I have removed the thermostat during all this repair, and it still overheats.
The overheat light inside the car never comes on, but the expansion tank boils over and my temperature reading on this portable gun shows around 220 F, so I shut down.

Cracked head symptoms and other overheating cures, please help?
 

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Probably MIA
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Bad head gasket or cracked head for sure. Its pushing combustion gases into the cooling system. You could perform a leakdown test before pulling it apart if you wanted.
 

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Jitterbug
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Test the expansion tank for combustion gasses with a kit, or do a compression or leakdown test before pulling the head off again.

When does it overheat, at idle without moving or when driving?

If at idle do the radiator fans come on?

Neat water won´t give the same thermal transfer properties as proper coolant so if you don´t find any other cause put a thermostat and G12 in and see what happens then.
 

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Probably MIA
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Test the expansion tank for combustion gasses with a kit, or do a compression or leakdown test before pulling the head off again.

When does it overheat, at idle without moving or when driving?

If at idle do the radiator fans come on?

Neat water won´t give the same thermal transfer properties as proper coolant so if you don´t find any other cause put a thermostat and G12 in and see what happens then.
Good point about testing for combustion gasses and to check on radiator fan operation. I had kind of just assumed he would have checked the fans already.

I do have to disagree on your last point though. Glycol (antifreeze), while it does raise the boiling point, it also is less efficient at transferring heat. For purposes of troubleshooting this car, putting G12 in would just be a waste of coolant. I design geothermal systems, currently working on one of the biggest in the country, so I do know about glycol. :cool:
 

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Discussion Starter #6
Thank you for the excellent advice.

Assuming it is a cracked head or perhaps a warped head.

Buying a new head is expensive, so I am looking for a machine shop to plane the head.

Other facts: I am not sure if it would overheat just idling, I'm a little impatient, so I rev it up. It takes about 10 minutes to overheat. I am sure if I drove it, it would overheat. The fans do kick on after it heats up. I did pull the head and examine it for cracks. None I could see. I put it back on with a new gasket kit and same thing, overheats.

I will try the leak down test and the compression test and report back. So far, I have enjoyed learning about this german car and the differences from this engine and american engines. My first impression is that German engines are somewhat more unforgiving in tolerances.

I will report back after the testing. Thank you.
 

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Probably MIA
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Have you verified that there are no blockages in the radiator or anywhere else in the cooling system?
 

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No NB Yellow Trifecta :(
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Thank you for the excellent advice...

So far, I have enjoyed learning about this german car and the differences from this engine and american engines. My first impression is that German engines are somewhat more unforgiving in tolerances...
... that they are ...
 

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Probably MIA
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How are you on wetting agents and the other additives in vehicle coolants?
They are completely useless and ineffective. Save your money.
 

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Catch me riding s00ty!
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Thank you for the excellent advice.

Assuming it is a cracked head or perhaps a warped head.

Buying a new head is expensive, so I am looking for a machine shop to plane the head.

Other facts: I am not sure if it would overheat just idling, I'm a little impatient, so I rev it up. It takes about 10 minutes to overheat. I am sure if I drove it, it would overheat. The fans do kick on after it heats up. I did pull the head and examine it for cracks. None I could see. I put it back on with a new gasket kit and same thing, overheats.

I will try the leak down test and the compression test and report back. So far, I have enjoyed learning about this german car and the differences from this engine and american engines. My first impression is that German engines are somewhat more unforgiving in tolerances.

I will report back after the testing. Thank you.

Just a thought, but:

1) Have you changed the timing belt & waterpump yet? In this instance, i'm more concerned that the plastic waterpump is just about shot and needs replacing. Even if your car has under 60k miles, its way past the recommended 7 year time on that plastic waterpump.

2) Have you changed your coolant temperature sensor? Sometimes, if that sensor is going bad, it doesn't really "sense" that the car is warm and it won't activate the cooling fans correctly. I would also look into changing the fan switch/sensor too because its the next sensor in line after the coolant temperature sensor. Also with the coolant temperature sensor, somewhere down the line, vw issued a TSB that included changing that sensor from the blacktop unit to the green sensor. That sensor is $9.99 at your local autoparts store or $27 at your local vw stealership.

Click here for the sensor
Click here for the Fan switch

3) Are you using the correct PINK G12 coolant? The green stuff that unfortunately most used Vw's come with as a stopgap solution is bad for these cars. That stuff starts to boil at a little over these car's normal operating temperature. It is also my belief that the green coolant slow destroys the coolant temperature sensor...

EDIT:
After rereading the original post, I think you should give my second and third suggestion a look.
 

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Probably MIA
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2) Have you changed your coolant temperature sensor? Sometimes, if that sensor is going bad, it doesn't really "sense" that the car is warm and it won't activate the cooling fans correctly.

3) Are you using the correct PINK G12 coolant? The green stuff that unfortunately most used Vw's come with as a stopgap solution is bad for these cars. That stuff starts to boil at a little over these car's normal operating temperature.
The coolant temp sensor you are speaking of has nothing to do with the fans. Its only purpose is to report coolant temp to the ECU for the fuel map and emissions controls, and also to trigger the overheat light. The cooling fans are controlled by a sensor that is in the lower corner of the radiator and the fan control module. Also, he said the fans are functioning so that is not the issue.

The only thing wrong with green antifreeze is the corrosion that it causes in the cooling system, particularly the aluminum head, radiator and heater core...and the fact that it is not compatible with G12. If mixed, they create a sludge. While G12's heat transfer properties are superior as well, the boiling point is no different than that of green antifreeze. Most vehicles (regardless of brand) operate in the 180-190F range, VW's are no different.

The OP has something more serious going on. He has gone through all the right motions and done the right checks with the exception of a leakdown test or test for combustion gasses in the cooling system. Water pump has been replaced, thermostat replaced, fans are working. Cooling systems are simple. He has fluid, he has flow (assuming the heater core isn't blocked). The only other possible cause is a cracked/warped head and/or failed head gasket.
 

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Discussion Starter #13
warped / cracked head

Follow up:

thank you so much for helping me get my first beetle bug up and running smoothly...

The overheating problem was caused by a warped head. I had bought the 1999 beetle used and obviously it had over heated and damaged the head. I picked up a new one and installed with help of a friend. It took me three weeks.

It runs great, burns a little oil, like maybe half a quart every couple tanks of gas, so I know there will be future work, but i love driving it, its makes me happy.

It has been wrecked twice since, I got it fixed.

First, the drivers side door was bent completely backward, but it was an easy fix, simply stuck a two by four in the door around the hinge and bent it back in place.

Then, a friend borrowed it and smashed the radiator shroud into curb, it did did a lot of damage.

I had to take off the radiator, drain fluid of course, disconnect air conditioner, put new shroud back in, put radiator back on, hook up air conditioner, get recharged...

No more letting friends drive, MY beetle bug...

thank you members for all the help.

Now its time to tweak it.

I put red velvet on the interior roof and arm rests in door.

I will post pics.

Corbotto
 
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