Coolant/Flashing red temp light

[MaJav]

Here’s my situation:
• Flashing Red Temperature & the audible beep
• No other indications or faults codes

This is the first time ever having the Flashing Red Temperature indicator on my dash. Lucky, I was at home and did not drive anywhere. I started doing some research & troubleshooting on this issue.

The owner’s manual provides the following information:
• Red light (Engine coolant temperature / level)
o If the light flashes in red when driving, first check the coolant level.
 Top up as necessary
o If the coolant level is normal, check the fuse for the radiator fan.
 Replace the fuse if necessary
 If fuse is not blown, the belt driving the water pump in not broken and the warning light still does not go out, do not continue driving because serious engine damage can occur.
o If the coolant level and the belt are normal, the fuse is not blown and the warning light has gone out, the malfunction may be in the radiator fan.

After reviewing and confirming the manual info, here’s are some of my checks & investigations:
• The G62 & G2 Engine Coolant Temperature (ECT) Sensor appear good.
o Checked resistance on this 4-pin sensor
 G62 (Pin 3 to 4) = 2830 ohm
 G2 (Pin 1 to 2) = 1302 ohm
• The Coolant Fan Control Thermal Switch – may be defective or is a normally open contact (sensor) until a high temperature is reach which turns on the fans.
o Checked resistance on the 2-pin sensor
 Pin 1 to 2 = 0 ohms
o Jumper the plug to this sensor – fans turn on.
o Started to pull this sensor out for additional inspection/test but stopped because of coolant fluid leaking out. Captured a small amount in a container and the coolant appeared okay.
• Checked the G32 Engine Coolant Level (ECL) Sensor
o Some strange indications during resistance checks.
 Pin 1 to 2 = 3.57 Mohm
• The Coolant Expansion Tank checks revealed that the fluid was mixed. The owner manual states – recognize G12 in the expansion tank by its red color. If the liquid in the expansion tank is brown, G12 has been mixed with another coolant additive.
o Very hasty stuff and will be flushing & replacing fluid.
o Not sure if this is the root cause of the Red Temp flashing
• Plans are to replace G62, G2 & Coolant Expansion Tank (G32 sensor part of tank) and of course the fluids with approved G12. Hopefully, this will resolve the issue.

One concern – this indication (Red Temp flashing / Beep) will also appear when the engine is cold and the key is turn on but not cranking on the engine. Starts out blue, then after about 1 min it goes Red & Beeps. This must be the standard diagnostic checks. After removing most of the Brown fluid from the expansion tank, rechecked the resistance which now reads about 7.8 Mohms. Will report results after replacing parts.

[MaJav]

Help?
What are the normal or expected readings for the following sensors?
1. G32 – Engine Coolant Level (ECL) Sensor
2. G62/2 – Engine Coolant Temperature (ECT) Sensor
3. Coolant Fan Control Thermal Switch; 2pin sensor

Thanks in advance

Here is a picture of the coolant remove from the Expansion Tank and some captured during Fan Control Thermal Switch checks.

[Smileybug]

One question would be what mileage do you have on your car?

[D2Beetle]

Of the top of my head I would flush it more than once (three times perhaps) and consider replacing... the thermostat, water pump and temps sensors, etc...

[MaJav]

Mileage: 100k

Could only get two of the new parts and these are the readings:
The G62 & G2 Engine Coolant Temperature (ECT) Sensor appear good.
o Checked resistance on this 4-pin sensor
 G62 (Pin 3 to 4) = 2219 ohm
 G2 (Pin 1 to 2) = 1016 ohm
• Checked the G32 Engine Coolant Level (ECL) Sensor
o Without fluids - resistance checks
 Pin 1 to 2 = 0 ohm
o With fluids - resistance checks
 Pin 1 to 2 = 278k ohm

The old G32 Engine Coolant Level (ECL) Sensor was shorted – always providing a high reading regardless of the fluid level. The sensor has two probes that extend into the expansion tank. Each probe should read about 0.4 ohm individually.

Then new G32 ECL Sensor did clear the High Temp (Red Flashing) & Beep indications on the dash. Now I need to understand what & how the other stuff got into the tank. One of the guys at the shop mentioned the Oil Cooler. Thinking about it – a recent oil change was just completed. Apparently, the oil cooler can be damage by over tightening? The small hose on top of the Expansion Tank is connected/associated with the oil cooler – not certain for sure but that is one area I will be investigating today.

[Smileybug]

At 100k, if you haven't already, replace the water pump and timing belt asap.

[gforce1108]

The small hose on top of the tank isn't associated with the oil cooler, but the oil cooler is part of the cooling loop. They are pretty sturdy, but do fail.

Make sure there was no antifreeze inside the electrical connector that attached to the tank. There's a known problem with the sensors failing and leaking antifreeze into the wiring harness. It's called coolant migration and causes all sorts of problems.

[kcosta]

OK so a few questions that I need help with. I have had my 2000 vw beetle for almost a year and have never had problems until now... the other day a red flashing oil can light came on only for a few seconds and went out.. I went checked the oil the next day got my oil changed and everything was fine. After getting my oil changed it is driving totally normal as usual. Today a red flashing heat light came on just for a few seconds so I pulled over and the light went out before I could stop so I stopped and turned off the car letting it sit a little and it didnt seem like there was anything else going on so then I kept going. It did it again about 30 minutes later but only for a few seconds again and then turned out. The only other time I have seen this light was when I turn my car on but it is blue and then goes out. What does all this mean???? I need some advice because I know nothing about it. Can I still drive it?

[Smileybug]

Step 1-check coolant levels
If thats low, top it off and you should be fine.
Other issue could be water pump if you haven't changed it yet.

[Fowvay]

It's a broken water pump impeller. It's an ultra common failure between 40,000 and 100,000 miles. Mine went just before 60,000 miles.

[puttersea]

Same thing just happened to my 2001 Beetle. Needs a new water pump. Mechanic said $1200. to fix.

Does this sound right?

[Smileybug]

For just the water pump, sounds like way too much. Better be doing the timing belt too. Even so, thats still pretty steep. Is that a quote from the dealer?

Also, did you overheat and keep driving? If there was damage done to the engine from overheating, that will up the cost.

[MaJav]

Lesson learned – my situation started with a Red Flashing Indicator & the audible beep. After researching available information, discovered the Expansion Tank Sensor was the faulty component. Easy check and situation can be reproduced by just unpluging the cable connector and the same indications will be displayed. However, during my inspection of the Expansion Tank – noticed the “milkshake” fluid in the tank which is not a good situation. Turned out to be a Faulty Oil Cooler - had an internal leak and was flowing oil into the coolant system.

Ended up replacing the Oil Filter Cooler, plus decided to do the Timing Belt/Water Pump replacement since the coolant would need to be drained. There are plenty of good references & procedures described by others on this site. One important item I overlooked was trying to take off & put back the new tooth belt relating to the tensioner. Lucky, I have plenty of metric bolts and was able to compress the tensioner but putting on the belt was still a tuff fight.

I ordered a timing belt/water pump kit from Diselgeek – even returned my call to confirm my questions. I also decided to replace two other sensors. The belt, pump and sensors were okay but I felt it was wise to change these items now – just in case.

The job took longer than I expected and my hands/arms are cut up pretty good. Plus, I got to get a good view of current conditions under the engine area. Filling the new coolant was a slow process – needed to take a few trip around the block to circulate the coolant fluid and top up as necessary.

Oh, as mention from others – You can check if the water pump is broken via the thermostat hole during a replacement or if want to comfirm the condition before diving into the timing belt/water pump replacement process.

Thanks to this form and everyone’s contributions.

[NEauto09]

posted the same thing on the last thread i read. we do the timing belt tensioner and belt atour shop on a 2.0 for 675. takes about 1.5-2.0 hours. a decent tech can do it in that time theyre not as complicated as made out when youve done20 a week for 4 yrs

[Turbomania]

I've had this same thing occurr. It happened the day after I had my coolant flushed and refilled. This occurred on the highway and fortunatly I had the remaining VW coolant in the rear. The reservoir was empty so it was a no brainer and turned out to be a low coolant situation caused by the VW tech. not allowing the engine to warm up completely enough so all the new coolant could circulate like it should. There was still air in the system. Fluid levels were put back to normal and I've had no problems since. Thanks, JK

[NEauto09]

seen that one before

[VWTBS]

The red temp light came on with a steady beep when the car was cold started this morning (about 47F). I had replaced the old coolant sensor with a green one earlier this year and coolant level was checked fine. What else could be causing this problem? It seems like it only acts up when the weather is cold. My car has 123500 miles on it and next timing belt/water pump change should be at 140000 miles. Any help would be appreciated

[D2Beetle]

Have you checked the expansion tank recently? The can crack and leak or the expansion tank sensor can go bad.

If your next TB/WP change is 140k and you have 123k, I would get it changed. Why wait and take the gamble.

[VWTBS]

I haven't checked the expansion tank, but I'm pretty sure there was no leak. I will take it to the shop next week to have them check on the expansion tank and sensor. If nothing's wrong with it then I may have to just get TB/WP done. By the way, I was wondering if a failing WP could cause any sort of light griding sound around where the alternator is. (I could only hear it on the passpenger side) Thanks.

[D2Beetle]

Originally Posted by VWTBS

I haven't checked the expansion tank, but I'm pretty sure there was no leak. I will take it to the shop next week to have them check on the expansion tank and sensor. If nothing's wrong with it then I may have to just get TB/WP done. By the way, I was wondering if a failing WP could cause any sort of light griding sound around where the alternator is. (I could only hear it on the passpenger side) Thanks.

Yes it could, as the water pump has bearings.