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Hi. I’m looking for a little help with hot, but not overheating 2004 NB 1.8T please!

Background:

I’ve recently replaced the water pump and timing belt after the original water pump failed and my car overheated. While doing this, I took the opportunity to flush the coolant system and replace the thermostat. As I was concerned the head gasket may have been damaged when the pump failed, I also checked the expansion tank for bubbling, the exhaust for water vapour, the cylinders for coolant and compression, and the oil for emulsion. The head gasket checks etc were good and the pump, belt and thermostat replacements all seem to be working. I filled the coolant system with only distilled water as I wanted to check it was tight and gain confidence in the new pump. Once this was done, I had intended to drain the coolant system and refill with 50/50 water/G13.

Problem:

I’ve now been testing/running the car for around 2 weeks. There are still no signs of a head gasket problem, the coolant system remains tight and the car drives well, but it’s running hotter than before and sometimes the temperature fluctuates quickly.

Temperature Measurement:

I’ve been using a bluetooth OBD2 dongle and the Torque app running on a smart phone to record the temperature.

Observations:

The car will warm up normally and I can draw heat from the heater core. After 6-10 miles of driving at 30-45 mph, the temperature is approximately 96 deg C.

Sometimes it can be steady at this temperature regardless of speed or traffic conditions. Other times the temperature will fluctuate between 94 deg C and 102 deg C dependant on traffic conditions.

The temperature also seems to change quickly with speed, for example cooling 3-5 deg C within a few seconds of driving faster.

The maximum temperature recorded so far has been 107 deg C. This was while standing in traffic. It quickly reduced once the car was moving again.

I’ve frequently seen 104-105 deg C while standing in traffic. On several occasions it has not reduced quickly once the car was moving and has taken several minutes to drop.

Both the fans operate.

The radiator hoses get hot.

I correctly get a blue cold coolant light when first starting.

I have not had a red coolant light other than when the pump first failed.

Thoughts and Comments:

I know the coolant system is pressurized and therefore won’t boil at 100 deg C. I think 107 deg C is too high and approaching the boiling point of pressurized water (or 50/50 water/G13).

The use of only water shouldn’t be a problem as water has a better thermal conductivity than 50/50 water/G13 and therefore the temperatures should be lower, not higher.

The old pump had a plastic impellor. The new pump has a cast metal impellor. Could the new pump be less efficient, resulting in reduced coolant flow through the system and higher temperatures?

I realise there is more airflow through the radiator with speed, but I wouldn’t have expected such a quick change in the temperature.

Also airflow alone doesn’t explain why the temperature would sometimes be steady or not reduce once moving.

Could my problems be owing to trapped air pockets? I’ve tried to “burp” the system when topping it up. It wasn’t filled under a vacuum.

Thanks in advance!
 

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My first thought; would be air in the cooling system, the 1.8T is notorius, for being hard to purge this air out of the system. That is why in the vw service manual, it is recommended to vacuum fill the coolant system and the reason, I finally bought a vacuum fill tool, in my case I bought the Uview Airlift with excellent results.


Basic check, would be a good idea with confirming, the return line is flowing well and not clogged, being important to purge the air out of the system and a positive indicator, the water pump is working as it should.

https://www.youtube.com/watch?v=SJN3biTfdGE

I have found; that my return line, had gotten clogged and this caused, air purge problems and restriction in coolant, returning to the coolant bottle. In my case, I removed the hose and ran some small wire, through the plastic restrictor in the hose and this fixed the problem.

A return line that kinda "spits" going into the coolant tank and if the heater doesn't get hot or is hot/cold intermittently, is another classic sign of air in the system.

This video; shows 2.0L but principles are the same, checking for flow and checking return line for clogging:

https://www.youtube.com/watch?v=ln4grYe3WnE

Here are some videos; discussing and showing, the use of a vacuum fill tool (Uview Airlift/Snapon tool shown in use):

https://www.youtube.com/watch?v=ADPxM2SC6Mc

https://www.youtube.com/watch?v=JnTUr0SEJBw

1.8T cooling system bleeding techniques without the use of a vacuum fill tool:

https://www.youtube.com/watch?v=A7zLr62CgVA

As for the operating temps; these fan and thermostat specs, can help give you an idea of operating temps and when these should kick on (fans) or open (thermostat):

Specs:

fans stage 1: come on @: 197-206 (92-97 C) degrees F turn off @ 197-206 degrees F (84-91 C)

fans stage 2: come on @ 201-221 degrees F 99-105 C): turn off @ 195-208 degrees F (91-98 C)

Specs: cooling thermostat operating parameters:

opening starts @ approx 185 degrees F (85 C)

fully open @ approx 221 F (105 C)

According to the Bentley; testing the thermostat is as follows:

"To quickly check if the thermostat is opening and if coolant is circulating through the radiator, allow a cold engine to run at idle and warm up. As the temperature of the coolant rises, carefully feel the heater and expansion tank hoses. They will get hot. Feel the radiator hoses, particularly the lower hose. They will stay relatively cool to the touch. When the thermostat opens the radiator hoses will quickly get hot and the radiator fans should cycle on shortly thereafter.

Check the radiator hoses. If they are not hot, then the thermostat has not opened or the radiator is clogged. If the hoses are hot but the radiator fan did not come on, troubleshoot the radiator fans."


They also say the correct g12/g13 coolant @ 50/50 dilution; will provide boiling protection to 226 F (108 C). Most of the time; when I am running water in a cooling system, is when I am working on a car and it has cooling issues and leaks. So, I cannot tell you; how a 1.8T would act with 100% water, for weeks like you. I always run coolant @ 50/50 and use the current VW spec G12+ or G13; depending on what is available.

Once you get the proper coolant in the system; maybe the temps will be different? When you go with the correct coolant; it will be interesting to see, if the temps change or if they act differently.

Temps wise; you do not sound out of range of what I see in my 1.8T and I live in the New Mexico desert with temps going over 100 F, during the summer. The engine can get pretty hot but when the cooling fans kick on at stage II; they bring the temps down effectively and the engine does not overheat, I have a recently replaced waterpump, thermostat with NO leaks in the cooling system.

Maybe, others can chime in; on what temps they see on their 1.8T but I also think, the thermostat and cooling fan specs, are a good indicator of normal temp ranges.

If your car was overheating; you will know it and the coolant light will come on. Here are the coolant light modes; for reference:

Blue coolant light = engine cold
Flashing blue coolant light = fault in the coolant monitoring system
Flashing red coolant light = low on coolant
Steady red coolant light = engine overheating, pull over and stop engine IMMEDIATELY and do not run until the problem has been identified.
 

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Where do you live, what are your current outside temperatures typically?

96C is the typical operating temperature on my 1.8t. I think I have seen my car get up to 100-102C while in traffic, do not think I have ever seen 107C. But again, what ambient temperatures are you talking about?

The 1.8t should purge air quickly and automatically in the cooling system. You mentioned the plastic water pump impeller was bad, do you think a impeller blade could have broken off and be stuck in the cooling system somewhere?

I would consider replacing the coolant temperature sensors and also monitor in the fans come on. There is also a problem with the 4 speed fan on these cars where one speed will fail and the fan will run too slow as I recall.

There is also a separate sensor for the fan as I recall in front of the coolant sensor, I think in the plastic "Y" fitting hear the front drivers side of the engine.
 

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Discussion Starter #5
Thanks for your feedback; it’s appreciated! I’ll try to answer all comments in one go...

The car is still running well, if a little hotter than I’d like. I keep “massaging” the coolant hoses to try and clear any air pockets. I don’t see any air bubbles coming up through the expansion tank thought. I’ve love to try a vacuum fill, but I don’t have a compressor, and having just bought a load of tools to fix the water pump, I can’t really justify it [to my better half]. Ha ha.

Thanks for tips on the return line and filling the coolant without a vacuum kit. I aim to check that this week. I’ll let you know how I get on.

Both fans seem to come on as the car heats up. I’ve not yet correlated the fans coming on with temperature. Guess I’ll do this if I find no problem with the return line above.

I checked the thermostat before re-fitting it, by placing it in a bowl of boiling water. While I obviously could get above 221F, I did observe the thermostat opening. Looked to be about a ¼ of an inch gap when open. I’ve also felt the hoses when the car is warm and both the upper and lower radiator hoses are hot to the touch.

I note the thermostat isn’t fully open until 221F. That would suggest that this temperature is within design intent for the coolant system. This combined with no overheating light/alarm would strengthen the argument that the car is okay. That aside I still don’t’ like the idea of my coolant reaching 225F, especially if G13 and water boil at 226F!

Just a side question, but what is the error of the temperature sensors? Could I be reading a few deg F high? I may look at replacing these, as they are cheap and easily done.

Local temperatures have varied lately between high 50F in the morning to low 80F in the afternoons. The car does seem to cope better in the morning [and the lower temperatures]. It normally takes around 10 miles to reach 100F. In the afternoon it is a few miles earlier, say around 5 miles. Much of this may be down to the traffic i.e. free running in the morning, bumper to bumper in the afternoon! That’s DC!

The old impeller was basically cracked in half. I’ll try to attach some pictures. Pushing the parts back together does show some minor bits are missing, but I’m hopeful these were washed out with the flush.

The auxiliary pump seems to be working. I haven’t tested for flow, but the pump is audible after first switching the ignition off. I’m not sure if it comes on while the engine is running.

The car is still running with distilled water only. One I’ve checked the return line, fans and temperature sensors, I’ll drain it and refill with the G13, using the method of pinching the hoses.

Thanks again.
 

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I think you have gone above and beyond with testing the cooling system. Let us know; the results of your continued testing and it couldn't hurt to replace the temp sensors. The fact that the car; has not over heated; since the water pump/thermostat were replaced, would indicate to me, that you are on the right track and the cooling system, seems to be working correctly.


Sent from AutoGuide.com Free App
 

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You have a problem. 10 miles to 100F!!

My 1.8t will get to 140F in 1 mile in 32F Temps. The Blue coolant temp light goes out at 140F as I recall.

You cannot test a thermostat by putting in boiling water and really understand what is going great on. The stat should start to open around the rated temp as I recall.

I would replace the coolant temp sensor at this time. Also keep in mind that a mix of coolant and water probably will run cooler than straight water.

The 1.8t will bleed or purge air without any effort via the small return line to the expansion tank.
 

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Discussion Starter #8 (Edited)
NB 1.8T Running Hot Affer Water Pump Replacement

Sorry... Typo. I forgot to convert to deg F. It was 100C in 10 miles i.e. 212F.

Thanks
 

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Discussion Starter #10
NB 1.8T Running Hot After Water Pump Replacement - Update

Okay, so the saga continues and I’m just about had enough of this car!

I’ve filled it with 50:50 G13 and water, burped it extensively and still the temperature rises.

Thurs it reached 225F before I got home. FYI, the ambient temperature as around 70F.

I then noticed that the fans were not coming on, so I followed the Bentley checks for the fans and sure enough both fans operate on high and low speeds when I jumper the respective terminals. With the fans and control module good, I opted to change the thermostatic switch on the rear of the radiator.

After re-filling and burping the system, the temperature again rose to 225F and none of the fans came on. I felt the bottom radiator hose and it was cold. The led me to check the thermostat. The thermostat opened correctly in a saucepan of boiling water, but I changed it anyway as I had done the work to get access anyway. BTW, a finger through the engine block to the water pump didn’t raise any concerns either.

After re-filling and burping the system once more, the temperature rose to 225F again. Still none of the fans came on and the bottom radiator hose was cold. I figured I may have a large air pocket in the radiator, so I disconnected the bottom hose from the thermostat flange. Water flowed freely from it if I opened the expansion tank cap.

Normally I’d think the water pump was defective, but I’ve only just changed that (for a metal impellor version) and the flow to the return line looks good.

I’m really stumped as to what could be going on here. Here are some thoughts:

Assumptions – the pump, radiator, fans, thermostatic switch and thermostat are good. Coolant and the system seems pressure tight.

Issue – there is a large air pocket in the engine block, which is preventing the thermostat coming into contact with coolant, heating up and opening.

Solution – Vacuum fill the coolant system.

I don’t have a vacuum fill or a compressor, but I could take the car to a shop to have the work done. Annoyingly this would waste the diluted G13 I already have, so I’ll only do this if there is a real possibility it will solve the problem.

Any help or comments would be great!
 

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All of your symptoms; in my experience, point to air in the system and a vacuum fill, would eliminate the problem. I got tired of this issue and bought myself a vacuum fill tool; as noted, seeing how the VW service manual, recommends using this tool, it is a known issue (no we are not crazy)! :)

The UView AirLift is pretty expensive but cheaper ones; have shown up, priced in the $40-$50 range now, on amazon and ebay. They look similar and are probably; cheaper asian offshore versions, of a similar design and operating tool. I figured, I was going to continue to work on my car myself and I was tired of struggling with air pockets! Using this type of tool deals with the issue, in a couple of minutes and you don't have to worry about it, ever again. I have used it on other hard to burp cars and you don't have to worry about air pockets, spending time burping things and can be confident, you have correctly filled the cooling system.

https://www.google.com/search?q=coolant+vacuum+fill+tool&oq=coolant+vacuum+fill+tool&aqs=chrome..69i57.4500j0j7&sourceid=chrome&ie=UTF-8

There have been a number of tools; that I have invested in, that have made a big difference in my repair process and a vacuum based coolant filler tool, is one of them. I always rationalize my tool investments and purchases; by figuring, I can pay someone else to do it or buy a tool, be able to do it as many times as I want and be ahead! :)

This has been a huge help and because; these cars, have leaks all the time, it will be used again, again, again and reduce, your down time, coolant repair process.

It does require a compressor; while I haven't tried it, you might be able to get away with a small one or some sort of mini one, you have lying around to fill up tires.
 

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Make sure the small hose that connects to the side of the expansion tank has coolant flowing through it.

You may have a blockage in this air bleed hose, I have found the 1.8t is self purging of air unless there is a problem.
 

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Discussion Starter #13
Things are getting better… but there are still gremlins at work!

I’ve done some more bleeding and the lower radiator hose now becomes hot and both fans switch on.

The fans seem to switch on at 103C (217F) and switch off again at 99C (210F). While the temperature can be seem to cycle, especially when standing in traffic, the temperature stays below 104C (220F), and the car is generally very drivable. As expected the temperature drops with airflow through the radiator. I now see 95-98C (203-208F) on the highway.

From fan testing (by jumpering the thermo switch terminals in accordance with the Bentley guide), the fans seem to be coming on at the slow speed only. They seem to run at the same speed when I switch the A/C on also.

At 103C (217F) I was expecting to see the fans run at fast speed as listed in the Bentley guide. I can’t explain why they do not, as when I jumpered the pins for the RED and RED/WHITE wires on the thermo switch connector, the fans seemed to run at slow speed, and when I jumpered the RED and RED/YELLOW wires the fans seemed to run much faster, presumably fast speed. Why would they run slow speed at 103C (217F) and not 92C (197F)?

Today, the car drove well for the first 13 miles. The temperature cycling nicely between 95-103C (203-217F) dependent on traffic and I had no concerns. I stopped the car to get groceries however and on re-starting the temperature was 105C (221F). I figured that was residual heat from the block and caused by the lack of cooling as I shut the engine off. I didn’t think more of it until it began rising to 110C (230F) by the time I got home, less than a mile later. On opening the hood, neither fan was running.

Can anyone thing of a reason why slow speed fans would start at the fast speed temperature and there would be no fast speed, especially when previously jumpering the thermo switch connector pins seemed to give the correct results?

Thanks for sticking with me on this one… I know it’s been protracted, but this NB seems to defy all logic!
 

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Discussion Starter #14
Sorry... guys more comments.

I’ve been trying to research the fan control module (FCM) to work out why my fans don’t seem to be working as they should.

Looking at the “Coolant Fan Control Module J293 Pinout – Vehicles With A/C Pressure Sensor G65 2000-2004 Golf/Jetta/ New Beetle 1.8L and 2.0L (Except Engine Code BBW)” on http://newbeetle.org/forums/questions-issues-concerns-problems-new-beetle/43260-summers-coming-here-check-your-fans.html, I can quite connect the dots…

1st Speed Fans

It looks like 1st speed (slow) fans will run when:

Inputs T14/3 (duty cycle) and T14/8 (fresh air blower switch & AC switch) are present, causing power to T4/2.

I can’t see however where a temperature of 92-97c (197-206F) would cause an output from coolant fan thermal switch F18 terminal 2 into the FCM resulting in the fans running at the 1st speed.

2nd Speed Fans

It looks like 2nd speed (fast) fans will run when:

1. A temperature in excess of 99-105C (210-221F) causes an output from coolant fan switch F18 terminal 3 to input T14/7 resulting in power to T4/4.

2. AC pressure sensor G65 sends signal to T14/3 to disengage compressor and provide power to T4/4 to run coolant fans during kick-down and high engine loading.

3. An output from coolant temperature sensor G2 (via instrument panel) to input T14/3 causes the AC compressor to switch off and the coolant fans to run at the 2nd speed. Is this also via T4/4?

I think I'm only interested in the parts in red text. If I can work these out I may be a bit closer it identifying a crossed wire or failed component etc.

Once again, thanks for sticking with me!
 

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You need to be careful on the fan configuration for these cars.

I think the 1.8t automatics had a 4 wire fan that was 3 speed.

The fan controllers often fail where one speed will not work so the fan may only run at 1 or 2 speeds?? I do not recall all of the issues these things have. I know the proper replacement fan is big $$$$ and many people skimp and install the cheap 2 speed fans that are easily and cheaply available.

95-98C sounds about the proper temperature. Also I know for a fact that the fans can and will run when the engine is at a specific temperature when the engine is shut off if everything is working properly.

You may want to read this guide, not VW, but it seems many of the multi speed fan controllers are very similiar and used on many different make and model vehicles. The BMW fan may be PWM controlled rather than fixed speeds like I recall the VW fans are, but it might be a good read and may generate some ideas.

https://drive.google.com/file/d/0B59e0P388oUjMDNkWDk5SkwxVlE/view

Also read these New Beetle specific links:

http://newbeetle.org/forums/1-8-liter-turbo/129042-cooling-fans.html

http://newbeetle.org/forums/1-8-liter-turbo/129042-cooling-fans.html
 

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fans

Sorry... guys more comments.

I’ve been trying to research the fan control module (FCM) to work out why my fans don’t seem to be working as they should.

Looking at the “Coolant Fan Control Module J293 Pinout – Vehicles With A/C Pressure Sensor G65 2000-2004 Golf/Jetta/ New Beetle 1.8L and 2.0L (Except Engine Code BBW)” on http://newbeetle.org/forums/questions-issues-concerns-problems-new-beetle/43260-summers-coming-here-check-your-fans.html, I can quite connect the dots…

1st Speed Fans

It looks like 1st speed (slow) fans will run when:

Inputs T14/3 (duty cycle) and T14/8 (fresh air blower switch & AC switch) are present, causing power to T4/2.

I can’t see however where a temperature of 92-97c (197-206F) would cause an output from coolant fan thermal switch F18 terminal 2 into the FCM resulting in the fans running at the 1st speed.

2nd Speed Fans

It looks like 2nd speed (fast) fans will run when:

1. A temperature in excess of 99-105C (210-221F) causes an output from coolant fan switch F18 terminal 3 to input T14/7 resulting in power to T4/4.

2. AC pressure sensor G65 sends signal to T14/3 to disengage compressor and provide power to T4/4 to run coolant fans during kick-down and high engine loading.

3. An output from coolant temperature sensor G2 (via instrument panel) to input T14/3 causes the AC compressor to switch off and the coolant fans to run at the 2nd speed. Is this also via T4/4?

I think I'm only interested in the parts in red text. If I can work these out I may be a bit closer it identifying a crossed wire or failed component etc.

Once again, thanks for sticking with me!
To answer your 1st fan speed question; The fans are turned on by the thermal switch mounted at the bottom corner of the radiator, if the duty cycle( A/C pressure switch is within range)and blower in cabin is set to at least one setting and A/C button is pushed in. Then when temperature rises that same switch sends a signal to the FCM and it sends 12vdc back to the other faster speeds on the fans. The 1.8T engines have a third input but only on the large fan.
To answer your 2nd speed fans question; when the coolant temperature rises to a specific high Level the pressure in the condenser rises above the cycle pressure switch and turns off the A/c compressor clutch, but at the same time the cpu is sending 12vdc to the FCM to turn on the fans in 2nd speed.
 

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temp. sensor

I do not think the 1.8t has a temp sensor in the lower radiator hose, or at least not all 1.8t configurations. The temp switch for the fans on my 1.8t is forward of the main coolant sensor in the manifold on the drivers side plastic manifold connected to the cylinder head.

This is the fan switch location in my 2003 1.8t:

http://newbeetle.org/forums/774839-post17.html

http://newbeetle.org/forums/1-8-liter-turbo/18279-what-sensor.html
The coolant temperature sensor is mounted on the plastic manifold flange and feeds data to the CPU. The 1.8t, well mine does have a thermo sensor mounted on the radiator bottom right as you face the motor and it controls the fans. I looked at the schematic personally a dozen times.
 

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So the engine coolant sensor is installed in the coolant flange that bolts directly to the driver side rear of the cylinder head

https://www.ecstuning.com/Volkswagen-New_Beetle--1.8T/ES2083247/

http://www.pelicanparts.com/techarticles/Volkswagen_Golf_GTI_Mk_IV/37-WATER-Coolant_Temperature_Sensor_Replacement/37-WATER-Coolant_Temperature_Sensor_Replacement.htm

The fan temperature sensor is installed in the upper radiator hose plastic junction that is forward of the coolant flange that mounts to the head, kind of near the battery.

See this hose and the pre-installed fan sensor

https://www.ecstuning.com/Volkswagen-New_Beetle--1.8T/Engine/Cooling/Hoses/ES297370/

This is how my car is set up, maybe not all 1.8t and all years are the same? I know that there are about 3-4 different 1.8t engine codes.
 
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