# 2009 VW Jetta 2.5 L overheating issues



## samweiz2011 (Nov 5, 2020)

Hello, I recently purchased an 09’ Jetta with overheating issues and no heat. Engine is at 160k miles. I first replaced water pump and thermostat. Still overheating. Next I flushed heater core lines(inlet/outlet) and this fixed the issue. I noticed big white chunks in the inlet of heater core. Car was driving fine for a couple of weeks then overheating started back up but I had heat coming out of vents but lower radiator hose was staying cold. I assumed thermostat was stuck closed so I replaced thermostat. Still overheating. Next I bought a mitivac and bled air out of system but still overheating. I did also verify cooling fans are coming on on radiator. Could it be bad water pump? Bad thermostat? Clogged radiator? In need of help. I was considering removing thermostat and running the car without it to see if any overheat occurred still.


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## samweiz2011 (Nov 5, 2020)

So I pulled thermostat out and no overheating occurs. Car does get up to operating temp (190). No heat coming out of vents(as expected) so bad thermostat? Should I test replacement in boiling water a few times before installing to make sure it opens?


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## Ichabod0525 (Feb 11, 2018)

I'd make the odd bet that the old thermostat opens when placed in boiling water and a second flush of the system produces more chunks. But you weren't looking for a bet so replacing the thermostat with a new OEM one seems reasonable. Doesn't hurt to test it first either. Good luck.


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## tharkhold (Apr 29, 2012)

Jack car on stands so front wheels are off the ground.

Start it and let it idle and get to optimal temp (95c).

Feel if radiator top is hot or cold when car is at that temp. Hot = thermostat ok, cold = thermostat not ok. At that point, engage the vents at max hot, so that will circulate the coolant in all the circuit. 

Next up, rev the engine to 1500-2000rpm, radiator fan should kick in. If the fan doesn't, it may be kaput, or the radiator temperature sensor (G83) could also be kaput. Note that on my car, my main fan died/intermittent, got a code, and I replaced it with a yard part. 

A restricted fan will throw a code. A borked radiator thermometer sensor (G83) WILL NOT give you a code. How do I know? My car is over heating only in low-urban driving, the radiator fan doesnt turn on, and this sensor is the only thing remaining to check as I've checked everything else and there are no codes being thrown at me.

VW cars are self-burping, so you shouldn't need an air bleeder to do this... but you wont damage anything if you do.


Last thought, when you replaced the water pump, did you see if there were any bits missing from the plastic impeller? If yes, these could have lodged themselves somewhere.


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## nekkidlad (Oct 4, 2013)

If you have white chunks of scale or buildup, you should probably run a flush with CLR or some other kind of scale/rust remover. It should help clear out more stuff that’s clogging up the system. Maybe even do it a few times jic if you see a lot of stuff coming out.

I had a truck before that I had to run 50/50 water/CLR through as a flush 3 times thru the system before it cleared out because it kept overheating. I had replaced the water pump and thermostat(because wp was leaking anyway and stat was right there...) but kept overheating after just not as fast, so put new fan in but still no luck. After the flushes never had an issue(sold it about 7 months after, never got past middle of the gauge).


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## samweiz2011 (Nov 5, 2020)

*Thanks for suggestions still troubleshooting*

Hello All,
Thanks for the suggestions. I really appreciate everyone taking the time and offering advice. I just read and will attempt to continue troubleshooting. Update on status. New radiator installed after additional coolant flushing. OEM thermostat installed. Fresh coolant added. Still overheating. When idle at lights around town but when driving seems to hold ok. I did also disconnect return line to expansion tank and did see good flow while car was running so I believe that means water pump is good? I also did hear squealing sound coming from somewhere (pulleys/idlers) ? Or something else. Hopefully not bad water pump bearing or drive belt issue?


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## samweiz2011 (Nov 5, 2020)

*Tharkhold*

Ok so I jacked up car on stands. Started it and let come up to operating temp. Upper radiator was warm, bottom was cold. Next I rev’d for about 5 min Fans did kick on.


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## rjm_vw (Jun 12, 2009)

I've never had any luck filling a VW without using a vacuum tool. I use the MasterCool 43013 with the rubber piece that goes into the fill bottle cut down to fit, but I'm sure there are plenty of other tools just as good. Using a vacuum tool has the added benefit of being able to verify if your cooling system is airtight before filling it with coolant, just draw a vacuum into the system and let it sit for 10-20 minutes.


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## Timbert (Jul 22, 2017)

I like to avoid using the dash gauge to diagnose in cases like this, using a VAG-COM is better. When the car was abused with the wrong coolant type or just filled over and over with tap water because of a leak, you can just say hello to all that calcium depending on how hard your tap water is. How big are "big" chunks?

Generally a very corroded system means the first most economical fix is a radiator replacement as that's where all the crud will be lodged, where the water passages are smallest, and maybe in heater core too. I have only once seen a water pump impeller fail, and it slid slowly off the shaft and eventually cut through the rest of the pump housing, causing a leak of course, but otherwise was circulating coolant just fine.

Also if you turn on the AC the fans will come on automatically, so that's an easy check to do. They should both turn at the same time and speed. Lastly, I personally think CLR is way too strong, and prefer to use the Prestone citric acid stuff, with distilled water, draining and refilling a half dozen times if necessary with a day or two of driving in between, the last few with the water only.


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## in2turbos (Jan 1, 2004)

Search Vw 2.5l overheats may 17 2020 I explained what it takes to remedy this situation flush with clr replace radiator and heater core


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