Coolant & Temp issue

[qwain]

I own a 2001 beetle 1.8L Turbo since Jan 2009. This is what happened to me tonight:

I was driving home and the Hot Liquid light (red) starts flashing. After a little I stop the car and check the coolant level and I notice that the bowl is full of coolant. The level is up to the cap!

I open the cap and the whole bowl is under pressure. Some gas comes out from the cap (after I opened) and it is very hot.

After that, I run the engine again with the coolant cap open. Now the level went down a lot, below the minimum.

Does anybody have an explanation for this? Am I safe to drive (at least to try if it does it again) or should I go straight to the mechanic?

[Smileybug]

How many miles? Flashing means overheating. I wouldn't be shocked if the water pump failed. Any coolant leaks noticable?

[qwain]

I drove for 1 mile or less. I was very very close to home when the light came on.

I never noticed any leak of coolant in the past, however tonight, when I opened the cap of the coolant bowl, some coolant came out (few cubic inches) because there was pressurized gas in the coolant bowl.

Any idea? Might it be a problem with the engine gasket?

[Smileybug]

How many miles on the car? Has the timing belt/water pump been changed?

[qwain]

100k miles

timing belt changed, water pump no

[chephron]

Now wait a minute, these symptoms could be several things.

1. Check to see if cooling fans come on with key in the engine on position but not cranked up. If they do not, it could be the fans are bad or one of three sensors are bad, coolant temp sensor (in the coolant flange), a/c cut-off sensor (to the left of the battery inside the coolant hose there, or the ThermoSwitch (on coolant hose at the bottom of the radiator on the driver's side).

2. Could be the Thermostat if it is not opening at the right time to let coolant in the engine and/or is sticking.

Because there is no mention of grinding noises or massive leaking of coolant onto the ground, its doubtful the issue is the waterpump in this case. Another question to ask is if you use green coolant at all? You should use only pink G12 VW stuff or parts can corrode in your coolant system causing failures.

[simonsi]

Originally Posted by qwain

I own a 2001 beetle 1.8L Turbo since Jan 2009. This is what happened to me tonight:

I was driving home and the Hot Liquid light (red) starts flashing. After a little I stop the car and check the coolant level and I notice that the bowl is full of coolant. The level is up to the cap!

I open the cap and the whole bowl is under pressure. Some gas comes out from the cap (after I opened) and it is very hot.

Your water pump is going, possibly the impellor is slipping on its shaft or it has broken, either way not enough circulation. The pressure is a red herring, even a fully functional system runs under 15psi pressure noramally. The level variation is what you get with boiling coolant inside the engine, it creates pockets of steam which causes the level in the bowl to change.

Dont remove the cap too quick when she is hot, fast way to get scalded.

[chephron]

"Could be the Thermostat if it is not opening at the right time to let coolant in the engine and/or is sticking."

This can cause back pressure and overheating, if it is not opening up properly and at the right time. I would start with the simple and work toward the more advanced, less likely causes. The fact that it didn't have the water pump changed with the T-belt like it should have and the fact that Beetles are known to have problems with the plastic impellors in their original water pump is clouding some people's judgement concerning this issue I think. Just my opinion...

The waterpump would be #3 on my list to check...

[Fl_bug]

Originally Posted by chephron

"Could be the Thermostat if it is not opening at the right time to let coolant in the engine and/or is sticking."

This can cause back pressure and overheating, if it is not opening up properly and at the right time. I would start with the simple and work toward the more advanced, less likely causes. The fact that it didn't have the water pump changed with the T-belt like it should have and the fact that Beetles are known to have problems with the plastic impellors in their original water pump is clouding some people's judgement concerning this issue I think. Just my opinion...

The waterpump would be #3 on my list to check...

Waterpump would be number 1 on my list only because he has over 100k miles and they normally start to fail around 60k miles... That, the thermostat, and the CTS usually go around the same time more or less

[simonsi]

Originally Posted by chephron

"Could be the Thermostat if it is not opening at the right time to let coolant in the engine and/or is sticking."

This can cause back pressure and overheating, if it is not opening up properly and at the right time. I would start with the simple and work toward the more advanced, less likely causes. The fact that it didn't have the water pump changed with the T-belt like it should have and the fact that Beetles are known to have problems with the plastic impellors in their original water pump is clouding some people's judgement concerning this issue I think. Just my opinion...

The waterpump would be #3 on my list to check...

Based on my experience actually. Also the first thing that would need doing after replacing the thermostat (even if that is the problem), is....replacing the water pump as it is well past its useful life....

I don´t subscribe to that thermostat failure rate, I´ve personally never seen it either on mine or a customers cars.

What is your #2 item?

[chephron]

Originally Posted by Fl_bug

Waterpump would be number 1 on my list only because he has over 100k miles and they normally start to fail around 60k miles... That, the thermostat, and the CTS usually go around the same time more or less

Waterpump = Expensive, not really doable at home for most people
Thermostat = Manageable at home, its overdue anyway and much cheaper
and may very well be the cause of the issue.

That's why I would start with the Thermostat if it were me. But then I troubleshoot from easy and likely to advanced. Its a philosophy that has always served me well. It helps keep down the possibility of expensive repairs that may not be necessary. Now if you have the money to go ahead and have both replaced at the same time, you will not be wasting as much coolant and will pick up the most reliability at the same time. But most people cannot afford to do it this way unless its absolutely necessary.

[Smileybug]

I wouldn't say thermostat is "overdue" unless its busted. I'm at almost 97k on my car with no thermostat replacement. You 'could' replace it when you do the pump/belt, but there isn't a real reason to. Pump and belt is the biggest priority in that service. For me, thermostat gets touched when it fails.

My bet goes to water pump.

[simonsi]

Originally Posted by chephron

Because there is no mention of grinding noises or massive leaking of coolant onto the ground, its doubtful the issue is the waterpump in this case.

If the waterpump impellor breaks or slips there will be no coolant leak - and I´ve never heard grinding noises from an impellor failure either. A WP bearing failure may give you noise and a leak (and it may also cause the engine to throw its timing belt and suffer catastrophic failure by valves hitting pistons).

You must be the only person I have ever heard of to rule out VW WP failure based on no leak and no noise.

[chephron]

Originally Posted by simonsi

Based on my experience actually. Also the first thing that would need doing after replacing the thermostat (even if that is the problem), is....replacing the water pump as it is well past its useful life....

I don´t subscribe to that thermostat failure rate, I´ve personally never seen it either on mine or a customers cars.

What is your #2 item?

If you re-read my original post my number 1 would be:

"Check to see if cooling fans come on with key in the engine on position but not cranked up. If they do not, it could be the fans are bad or one of three sensors are bad, coolant temp sensor (in the coolant flange), a/c cut-off sensor (to the left of the battery inside the coolant hose there, or the ThermoSwitch (on coolant hose at the bottom of the radiator on the driver's side)" Though there is the possibility that since we haven't heard whether it overheats at idle yet or not that these are not the cause, but they will need doing anyway especially at that mileage.

My number 2 is the Thermostat, and 3 the Waterpump

But knowing Beetles, it would be good to replace all of it if at all possible, given that every part I have
mentioned above is prone to failure especially over 100K.

[simonsi]

Originally Posted by chephron

...It helps keep down the possibility of expensive repairs that may not be necessary...

You are missing the point, his WP is necessary, right now. You can change the tstat and CTS and anything else you like but at the end of that....his WP needs doing right now.

...and his engine is giving classic VW WP poor circulation symptoms.

So WP now or....now??? Doesn´t matter if it is doable at home or not, it still needs doing.

[Fl_bug]

6 years or 70k miles is usually it... But he has 9 years and 100k miles..

Here is a video that explaining the waterpump failures.

[simonsi]

Originally Posted by chephron

If you re-read my original post my number 1 would be:

"Check to see if cooling fans come on with key in the engine on position but not cranked up. If they do not, it could be the fans are bad or one of three sensors are bad, coolant temp sensor (in the coolant flange), a/c cut-off sensor (to the left of the battery inside the coolant hose there, or the ThermoSwitch (on coolant hose at the bottom of the radiator on the driver's side)" Though there is the possibility that since we haven't heard whether it overheats at idle yet or not that these are not the cause, but they will need doing anyway especially at that mileage.

My number 2 is the Thermostat, and 3 the Waterpump

But knowing Beetles, it would be good to replace all of it if at all possible, given that every part I have
mentioned above is prone to failure especially over 100K.

If I go to my car and do what you say the fans don´t come on. The car is fine but the engine is cold so they shouldn´t come on. I think you need to clarify to the OP what you want him to do...are you suggesting changing all three sensors and the fans just based on mileage???

[chephron]

Originally Posted by simonsi

If the waterpump impellor breaks or slips there will be no coolant leak - and I´ve never heard grinding noises from an impellor failure either. A WP bearing failure may give you noise and a leak (and it may also cause the engine to throw its timing belt and suffer catastrophic failure by valves hitting pistons).

You must be the only person I have ever heard of to rule out VW WP failure based on no leak and no noise.

If you read everything I wrote, I did not rule out a WP failure. Its just not my first thing to replace. When impellor bearings break, if you look at the physics of it, the impellor blades strike the WP casing causing an audible noise (for a few minutes) and causing improper flow of coolant and the likelihood of unusual pressure in the waterpump causing extra pressure in the coolant system sending back pressure that builds in the bottle. That's where the leaks unusally come from. But perhaps you are right about the timing problems which is another clue that they WP may not be the immediate issue. Though it is way over due to replace it anyway.

[chephron]

Originally Posted by simonsi

If I go to my car and do what you say the fans don´t come on. The car is fine but the engine is cold so they shouldn´t come on. I think you need to clarify to the OP what you want him to do...are you suggesting changing all three sensors and the fans just based on mileage???

They are supposed to come on when you put it into the Engine on position, NOT accessory AND put on the AC and fan speed set to high. If they don't you have a problem. You have a high and low one, it doesn't have to be hot for them to come on when the AC is on. This is all basic troubleshooting.

[chephron]

I once replaced a fuel pump JUST based on mileage.