NMS overheat...faulty pump changed

J

JETaah

Vendor , w/Business number
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Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 2005 BEW Beetle, 2005 Jetta Wagon
Have a Passat NMS 2012 in the shop because it overheated pretty badly one night recently driving on the freeway. I found the coolant pump impeller loose on the shaft, replaced it with timing belt service that was well over due but, I don't know if that is all that is wrong.

Owner complained that the heater did not work on the occasion of the overheating incident but said it was not previously a problem. I imagine that the heater core would not necessarily get hot if the pump was not pushing coolant.


The EGR cooler has been removed along with the exhaust, turbo back.


I did discover the flaky residue when I strained the coolant that I extracted.
As it is now the coolant temp seems to be running about 204*F (96*C) on this day which is 77*F...not really hot. Flat ground, pushing it on occasion at WOT... cooling system should be able to handle it, no? radiator fans are coming on.

Here is the readout via VCDS:
Address 01: Engine (03L 997 009 J)

16:18:33
IDE00025 Coolant temperature 96 °C
IDE00192 Coolant temperature at radiator outlet: actual value 46.3 °C
IDE00194 Coolant temperature at radiator output: specified value 95.0 °C

Does that look like too big of a temp drop for the thermostat to be working correctly?at all?
 
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7

740GLE

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NH
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2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
IMO clogged coolant system due to coolant breaking down, flush the radiator and everything else you can.
 
J

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 2005 BEW Beetle, 2005 Jetta Wagon
Would there be any point to using a cooling system elixir (Prestone Radiator Flush and Cleaner)?
 
aNUT

aNUT

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Joined
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Location
Boulder, Colorado
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'01 TT (ALH-ish), B7 Audi gasser, '05 Golf
This customer's car probably has a cracked head. Seen 2 CKRAs like this. 2 symptom sets from here:

1 - Combustion chamber gasses pressurize the water jacket which causes coolant ejection from the reservoir. This gets mistaken as an overheat w/ boil over.

2 - Combustion chamber gasses displace coolant from radiator preventing effective heat rejection.

To test: w/ engine cold & cooling system filled, open reservoir cap to ensure zero pressure. Reinstall. Start engine. Raise idle speed to ~2K for ~120s. Turn off engine. See if cooling system builds pressure. It shouldn't. If it does, car probably has a cracked head. Maybe a HG issue, but the cracked head is much more common.

You can rule out the remote possibility that the IC or EGR cooler are leaking pressure into cooling system by divorcing flow/pressure to/from them with hose pinch pliers.

All that being said, CKRA t-stats are kinda janky, and I've seen them fail. There are a few threads related to CKRA t-stats that don't open up until water temp is pretty high. PITA job. To test - get the car at operating temp where t-stat should be open. Unplug fans so you can get you hand in there to see if outlet radiator hose gets hot when car is not moving w/ engine at idle. If T-stat is opening, outlet radiator hose will get warm.
 
J

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 2005 BEW Beetle, 2005 Jetta Wagon
aNUT said:
This customer's car probably has a cracked head. Seen 2 CKRAs like this. 2 symptom sets from here:

1 - Combustion chamber gasses pressurize the water jacket which causes coolant ejection from the reservoir. This gets mistaken as an overheat w/ boil over.

2 - Combustion chamber gasses displace coolant from radiator preventing effective heat rejection.

To test: w/ engine cold & cooling system filled, open reservoir cap to ensure zero pressure. Reinstall. Start engine. Raise idle speed to ~2K for ~120s. Turn off engine. See if cooling system builds pressure. It shouldn't. If it does, car probably has a cracked head. Maybe a HG issue, but the cracked head is much more common.

You can rule out the remote possibility that the IC or EGR cooler are leaking pressure into cooling system by divorcing flow/pressure to/from them with hose pinch pliers.

All that being said, CKRA t-stats are kinda janky, and I've seen them fail. There are a few threads related to CKRA t-stats that don't open up until water temp is pretty high. PITA job. To test - get the car at operating temp where t-stat should be open. Unplug fans so you can get you hand in there to see if outlet radiator hose gets hot when car is not moving w/ engine at idle. If T-stat is opening, outlet radiator hose will get warm.
Click to expand...

He did not loose coolant to speak of...the reservoir was near empty but not much below that so it may have pushed some out but, his temp gauge got real high ...near 260F if I remember correctly. Don't forget that the coolant pump impeller was freewheeling on the shaft. There is no discoloration of the reservoir from combustion gases. He commented that the car's coolant temp gauge has always read closer to 200*F for as long as he's owned it...which means it probably has run higher than 200F.
 
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aNUT

aNUT

Vendor , w/Business number
Joined
Nov 29, 2006
Location
Boulder, Colorado
TDI
'01 TT (ALH-ish), B7 Audi gasser, '05 Golf
So is the car still overheating? Maybe I misinterpreted. Thought you were saying it was still overheating after replacing the failed pump.
 
J

JETaah

Vendor , w/Business number
Joined
Jan 18, 2001
Location
mi 48836
TDI
96 B4V, 2005 BEW Beetle, 2005 Jetta Wagon
aNUT said:
So is the car still overheating? Maybe I misinterpreted. Thought you were saying it was still overheating after replacing the failed pump.
Click to expand...
It is.
Put it this way...it runs hotter than 190*F. But, I did not get it to reach 260 again.
 
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