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View Full Version : Car filled with concentrated coolant, overheated and no longer fires. (2.8l)



Tozaco
09-04-2018, 04:12 PM
My 1998 Audi A4 with the 2.8l V6 started throwing a coolant temperature sensor error, so I replaced the sensor. With my poor decision to trust an "expert" the coolant was filled with concentrate and without bleeding while I was grabbing my Haynes manual. We went ahead with the normal coolant refill instructions after the initial refill, which seemed fine then I drove the car ~10 miles to drop it off somewhere. It didn't have a problem on that drive and the original problem was fixed and I didn't think much more of it afterwords.

Fast forward a week and while driving my coolant temperature sensor blew out spewing coolant all over leaving a nice cloud behind me, then my coolant warning light turned on. I guess I should pay more attention to the coolant temp gauge. Towed the car home and replaced with proper coolant and sensor, the car started and ran fine a few times while getting the coolant level right. Once it was level I drove the car around the block, and just a minute after parking the engine cut out.

I deferred to my repair manual and couldn't find anything related, so I started the car again and got it to operating temperature where it started to die again, video here https://streamable.com/qsih2 . I turned the engine off at the end because I wasn't sure if I should keep it on. After that video the car would only turn over but not fire. No codes were stored, really clueless as to look into.

Are there any problems that arise specifically in response to the engine over heating? Previous to the coolant change it was running fine, so my only ideas are 1)over heating caused problems or 2)coolant that sprayed out of the sensor location is causing problems

KSEADUB
09-04-2018, 09:31 PM
Might be totally un-related. You have a check engine light, so Id scan for codes first.


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Tozaco
09-05-2018, 01:44 AM
Might be totally un-related. You have a check engine light, so Id scan for codes first.


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I checked for codes with my VAGCOM cable, but there were none stored. If you look a the video you can see the check engine light disappears soon after it appears.

Are there any problems that arise specifically in response to the engine over heating? Previous to the coolant change it was running fine, so my only ideas are 1)over heating caused problems or 2)coolant that sprayed out of the sensor location is causing problems

walky_talky20
09-05-2018, 04:56 AM
Are you certain the engine overheated during the sensor blow-out incident? Generally even during extreme overheat, the sensors don't just pop out. They are held in pretty firmly when installed properly. However, it is pretty easy to install them "half clipped" if you aren't careful. This can cause a blow-out later on, just under normal operating temperature/pressure. Your coolant light would have come on merely due to the reservoir running low after the leak occurred. The coolant "low level" and coolant "overheat" dash warnings are identical.

If there was damage from an overheat, the thing would not run smoothly. Especially when cold. In your case, it seems to have run normal until it cut out and will not fire again. Although I can't say for sure, that sounds more like an electrical issue. Perhaps caused by the moisture from the coolant leak.

The first steps I would do:
- Confirm spark during cranking.
- Confirm injector pulse during cranking.
- Confirm fuel pressure during cranking.
- Confirm good compression on all cylinders.

KSEADUB
09-05-2018, 06:58 PM
Sounds like walkys got ya covered!


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Tozaco
09-05-2018, 09:13 PM
It's possible the sensor wasn't entirely clipped in when it failed, but my engine coolant temp was definitely past center when it happened. I don't think it was all the way to H though

It seemed like it may have been running rough when it was revved over 2k, but I hadn't driven it hard to really check.

That's a good list though so I should be able to check everything but the fuel pressure tomorrow because I don't have the gauge needed

thanks!