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Discussion Starter #1
I believe this is a common problem on Beetles. Since it doesn't have a coolant temp gauge(only the blue/red light which goes blue when cold, goes out when normal and goes red when overheating/level low) it's difficult to tell whether the engine temp is normal or a bit high.

My car has been experiencing hard starting for a long time and today after I reached home I immediately hooked my computer and VAG-COM cable and found that the coolant temp was 106.5 degree celsius. Did a research and confirmed it's a bit high(the coolant light doesn't come on when driving I believe it won't go on below 120 degree celsius). Checked the coolant ok, water pump is new, checked the cooling fan and found that only the large fan working on high speed, neither fan work low speed, the small fan doesn't work high speed either. Checked the voltage supply to the fan OK, therefore the fans are bad. Ordered new unit and it's going to arrive Tuesday. Hope this solves the hard starting problem(might be piston ring stick to cylinder I guess)

I think the large fan still works on high speed this prevents the engine from overheating. This is probably why the red light doesn't come on. However red light doesn't come on doesn't indicate the cooling system working properly. Therefore I believe everyone should check the coolant temp periodically as the vehicle ages.
 

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I believe this is a common problem on Beetles. Since it doesn't have a coolant temp gauge(only the blue/red light which goes blue when cold, goes out when normal and goes red when overheating/level low) it's difficult to tell whether the engine temp is normal or a bit high.

My car has been experiencing hard starting for a long time and today after I reached home I immediately hooked my computer and VAG-COM cable and found that the coolant temp was 106.5 degree celsius. Did a research and confirmed it's a bit high(the coolant light doesn't come on when driving I believe it won't go on below 120 degree celsius). Checked the coolant ok, water pump is new, checked the cooling fan and found that only the large fan working on high speed, neither fan work low speed, the small fan doesn't work high speed either. Checked the voltage supply to the fan OK, therefore the fans are bad. Ordered new unit and it's going to arrive Tuesday. Hope this solves the hard starting problem(might be piston ring stick to cylinder I guess)

I think the large fan still works on high speed this prevents the engine from overheating. This is probably why the red light doesn't come on. However red light doesn't come on doesn't indicate the cooling system working properly. Therefore I believe everyone should check the coolant temp periodically as the vehicle ages.

The small fan actually cools the condenser for the AC as well as the radiator. That could in fact be your problem however 106C is well within the threshold of the car's normal operating temperature especially with the ambient temperature outside being what it is.

Now you do need to replace the small fan less your AC compressor goes kaput and you can only get cold air while driving.

And yes I hate that it has no real temp gauge GRR I might add one some day
 

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Not really a high temp and I can't see it causing any sort of starting problem TBH.

Hard starting hot, cold or both?

Quite often the temp sensor will die and give a false high reading so when cold the engine meters fuel for warm so gives difficult cold starts.
 

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Discussion Starter #4
Not really a high temp and I can't see it causing any sort of starting problem TBH.

Hard starting hot, cold or both?

Quite often the temp sensor will die and give a false high reading so when cold the engine meters fuel for warm so gives difficult cold starts.

Not very hot, at least not high enough to trigger the coolant temp light. But it's a possibility because I've replaced a lot of stuffs and can't think anything else.

Hard starting only hot. It's that after shutting down in a couple of minutes it's easy to start. After that period of time it becomes very hard to start.

I know that the sensor dies sometimes but mine seems to be OK...
 

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Discussion Starter #5
The small fan actually cools the condenser for the AC as well as the radiator. That could in fact be your problem however 106C is well within the threshold of the car's normal operating temperature especially with the ambient temperature outside being what it is.

Now you do need to replace the small fan less your AC compressor goes kaput and you can only get cold air while driving.

And yes I hate that it has no real temp gauge GRR I might add one some day

The ambient temp is not exceeding 30C. The 106C is several minutes after shutting down and the real running temp might be 110 or more I believe...
 

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Jitterbug
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Not very hot, at least not high enough to trigger the coolant temp light. But it's a possibility because I've replaced a lot of stuffs and can't think anything else.

Hard starting only hot. It's that after shutting down in a couple of minutes it's easy to start. After that period of time it becomes very hard to start.

I know that the sensor dies sometimes but mine seems to be OK...
The sensor has two windings in it, one feeds the ECU for the light, the other feeds the ECU for fuelling. Entirely possible for it to work correctly for one but not the other.
 

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Jitterbug
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The ambient temp is not exceeding 30C. The 106C is several minutes after shutting down and the real running temp might be 110 or more I believe...
Ah, after a coulle of minutes post shutdown the heatsoak will probably have pushed the temp UP.

put your laptop on the passenger seat and look at the temp data blocks in real time as you drive, bet she is normal. Heatsoak is why the fans can run at low speed AFTER shutdown to get rid of the residual heat...
 

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The sensor has two windings in it, one feeds the ECU for the light, the other feeds the ECU for fuelling. Entirely possible for it to work correctly for one but not the other.
Correct! I just replaced mine cause of that problem. The coolant light worked correctly, but would dump a lot of gas at start up, engine would be hot but it was thinking it was cold. It was so hard to start if I stopped somewhere while I'll was out driving.
 

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Discussion Starter #9
well after I replaced the fan I kept monitoring the coolant temp. However, it's still high, although lower than before. Now it becomes around 100C. The fans start at 100.5C and cuts out at 99C. I replaced the coolant temp sensor today and it still shows the same temp. This makes me to believe the fan switch is probably bad. I'm going to replace it tomorrow since it's fairly cheap($30.xx from Autozone) and see what goes on else.
 

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Jitterbug
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well after I replaced the fan I kept monitoring the coolant temp. However, it's still high, although lower than before. Now it becomes around 100C. The fans start at 100.5C and cuts out at 99C. I replaced the coolant temp sensor today and it still shows the same temp. This makes me to believe the fan switch is probably bad. I'm going to replace it tomorrow since it's fairly cheap($30.xx from Autozone) and see what goes on else.
Still after shutdown? If so its still heat soak and not harmful at those levels.

When you are driving the fan thermal switch won't be called upon as there is sufficient airflow from driving.
 

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Discussion Starter #13
Still after shutdown? If so its still heat soak and not harmful at those levels.

When you are driving the fan thermal switch won't be called upon as there is sufficient airflow from driving.

I tested it when idling. I know about the heat soak so I'm not testing it after shutdown. The fan thermal switch is supposed to be called when idling if the coolant temp go beyond set point right?
 

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Discussion Starter #14
I have posted this on a thread or two recently. These are the Bentley diagnostics for the cooling system. Have you run these? Crazy to just keep replacing parts, trial and error. Of course when your done, everything is new. ;)

MORAV

Thank you for the info. BTW, do you have the whole Bentley manual that I can take a look?

I tested them already and the coolant is brand new from dealer and mixed with same volume distilled water. I tried to jump the thermal switch and the fan didn't work. Tested the voltage at fan connection to be exist so fans are bad. Replaced the fan then jumped the thermal switch connector both fans work(I used a very thin piece of wire to jump and the huge current almost burned the wire...). This indicates that both fans and control module work good. However when idling the VAG-COM showed that the fans come on when coolant temp is 100.5C and then shuts off after like 20 seconds when coolant temp shows 99C. Therefore I think it's either the coolant temp sensor or the fan switch. I don't want to test them because I need to drain the coolant, get them out and measure when boiling. If I simply replace them I don't need to drain coolant(just let it flow out a little and then seal it immediately). And they are fairly cheap so I decided to replace them one by one. Did a research that the ECT tends to be bad more so replaced it first. No good. So replaced the fan switch yesterday. Today the hurricane is coming so not going out. I'll update next week probably. Thanks everyone.
 

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I tested it when idling. I know about the heat soak so I'm not testing it after shutdown. The fan thermal switch is supposed to be called when idling if the coolant temp go beyond set point right?
Not quite, the fan thermal switch is called when the radiator temp goes beyond a certain point, measured at the radiator itself, not at the coolant sensor.

You can't predict fan behaviour by coolant temp measured by the CTS.

Two different scenarios:

Start engine, thermostat is stuck closed. Engine will boil before fan thermal switch detects a problem and turns the fans on.

Towing, thermostat sticks open, after shutdown fans will run for a short period despite CTS showing below normal temp. Fans run to dissipate residual heat in the radiator.
 

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Thank you for the info. BTW, do you have the whole Bentley manual that I can take a look?
Yes, I have the whole Bentley manual. I have the paper Bentley "Service Manual" and the DVD-ROM Bentley "Repair Manual". They are not the same, however both contain some of the same information. The paper manual is more geared to the DIYer, while the DVD-ROM is written for the experienced Tech.
To post anything from the paper manual, I have to first copy the pages, one by one, scan them into a .pdf file and then upload them. Posting from the Bentley, I have to capture what I want to post with a third party program, save it into my computer, and then post it up. Not as easy as simply posting the manual. While I have never checked, and I've never seen it discussed on here or any other Forum, it should be available at your local library.The ISBN number for the version I have is 978-0-8376-1542-4. We have all just become too dependent on the web for everything.

You obviously are not strapped for cash, and you obviously know enough of the basics to put the manual to use. You already have the VAG cable and computer program. Why not buy a paper, they can be bought all around the web for <$100, and buy a DVD-ROM (ditto the price). You can even buy the DVD-ROM Download directly from the Bentley site. If you were a certfied Tech, you probably would'nt need the paper (it's kind of like a training manual), but I have found the paper only takes you to a certain level, hence the need for the DVD-ROM. Then uste the Org to supplement the two. They are really an insignificant investment, that will pay for themselves very quickly if you do any significant amount of DIY work on your Bug. I have also read that the Haynes manual contains a fair amount of info that IS NOT in the Bentley, so apparently the Bentley is not the end all of NB manuals. I see them on eBay for $20-$30.

As to your immediate situation, I'd have to review the manual v. what you have done, and proceed from there (not having any direct experience with your situation), which you can do yourself. Sounds like you are on the right track, but review what you have done, check that you haven't missed something or mis-read something. "simonsi" seems to be a knowledgeable poster, just sometimes hard to follow. I'll be glad to look for, and post up or p/m you with any information you feel you need that might be helpful. P/m me though, as it's easy to miss a post in a thread.

M.
 

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Discussion Starter #17
Yes, I have the whole Bentley manual. I have the paper Bentley "Service Manual" and the DVD-ROM Bentley "Repair Manual". They are not the same, however both contain some of the same information. The paper manual is more geared to the DIYer, while the DVD-ROM is written for the experienced Tech.
To post anything from the paper manual, I have to first copy the pages, one by one, scan them into a .pdf file and then upload them. Posting from the Bentley, I have to capture what I want to post with a third party program, save it into my computer, and then post it up. Not as easy as simply posting the manual. While I have never checked, and I've never seen it discussed on here or any other Forum, it should be available at your local library.The ISBN number for the version I have is 978-0-8376-1542-4. We have all just become too dependent on the web for everything.

You obviously are not strapped for cash, and you obviously know enough of the basics to put the manual to use. You already have the VAG cable and computer program. Why not buy a paper, they can be bought all around the web for <$100, and buy a DVD-ROM (ditto the price). You can even buy the DVD-ROM Download directly from the Bentley site. If you were a certfied Tech, you probably would'nt need the paper (it's kind of like a training manual), but I have found the paper only takes you to a certain level, hence the need for the DVD-ROM. Then uste the Org to supplement the two. They are really an insignificant investment, that will pay for themselves very quickly if you do any significant amount of DIY work on your Bug. I have also read that the Haynes manual contains a fair amount of info that IS NOT in the Bentley, so apparently the Bentley is not the end all of NB manuals. I see them on eBay for $20-$30.

As to your immediate situation, I'd have to review the manual v. what you have done, and proceed from there (not having any direct experience with your situation), which you can do yourself. Sounds like you are on the right track, but review what you have done, check that you haven't missed something or mis-read something. "simonsi" seems to be a knowledgeable poster, just sometimes hard to follow. I'll be glad to look for, and post up or p/m you with any information you feel you need that might be helpful. P/m me though, as it's easy to miss a post in a thread.

M.


Good. Thanks a lot. I can obviously buy one at a very reasonable price and I'm not strapped on cash though... I just don't think the Bentley manual helps too much to me because all I need is just the torques of the bolts and some of the specifications like normal coolant temp...I just wanna know is there any differences between the bentley manual and the Haynes manual(I already have one that the previous owner passed to me), I mean the torque specifications.
 

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Discussion Starter #18
Not quite, the fan thermal switch is called when the radiator temp goes beyond a certain point, measured at the radiator itself, not at the coolant sensor.

You can't predict fan behaviour by coolant temp measured by the CTS.

Two different scenarios:

Start engine, thermostat is stuck closed. Engine will boil before fan thermal switch detects a problem and turns the fans on.

Towing, thermostat sticks open, after shutdown fans will run for a short period despite CTS showing below normal temp. Fans run to dissipate residual heat in the radiator.

Got it. I just replaced the thermostat with a new one and flushed the cooling system, refilled with 50/50 G12. I touched the upper and lower hoses and I'm sure the thermostat is open. But it's not common that the ECT sensor shows over 100C the fan is still not started right? I read the bentley manual that the fan should start when the thermo switch gets signal of like 89-93C so it's not likely that the ECT is getting 100C the radiator thermo switch is getting under 90C when the thermostat is open and coolant circulating(The water pump is new).
 

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Jitterbug
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Got it. I just replaced the thermostat with a new one and flushed the cooling system, refilled with 50/50 G12. I touched the upper and lower hoses and I'm sure the thermostat is open. But it's not common that the ECT sensor shows over 100C the fan is still not started right? I read the bentley manual that the fan should start when the thermo switch gets signal of like 89-93C so it's not likely that the ECT is getting 100C the radiator thermo switch is getting under 90C when the thermostat is open and coolant circulating(The water pump is new).
Quite easy if there is airflow through the rad, the rad is very efficient at dropping the coolant temp.

If in doubt (and you can't just go on the CTS), borrow a laser temp and measure the rad temp.
 
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