Diagnose thermostat/temp sensor issues, when no errors show up

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
Depends on the ambient temperature and one's cabin heater settings. My Golf will only reach ~170F at wee hours of the morning with the heater fan on low. Coming back a few hours later I can reach 195.8 F if I keep the fan off. I changed the t-stat this past Dec. What concerns me is the lower radiator hose never gets warm; yet I see good return flow to the reservoir.
 

halfbytecode

Well-known member
Joined
Oct 7, 2017
Location
S
TDI
1.6 TDI - CR, 2010 Polo Sedan
It seems there is indeed carbon build up, which affects the car's performance. I drove it on the highway, while keeping the revs at about 2500, for about 10 minutes.

It made a significant difference. I have also done this a number of times in the past, and I have always had success, but I want to find a long term solution to this issue.

I am thinking the EGR valve would be dirty as well, considering the mileage on my car. However, accessing the EGR is a pain, and I really want to avoid that, if I can.

It seems flushing the engine has helped some people, with similar mileage on this specific engine.
 

Henrick

Top Post Dawg
Joined
Aug 24, 2010
Location
Ireland
TDI
Golf VI TDI, 77 kW (CAYC)
Trust me, it's not carbon buildup what's causing issues. You will be surprised but the EGR valve is clean. It's on the hot side of the exhaust, the dry soot gets blown away. Most gunk is there the cooled exhaust meets intake plumbing (due to oil vapour, etc).
Don't waste your time cleaning it, not really worth on this engine
 

halfbytecode

Well-known member
Joined
Oct 7, 2017
Location
S
TDI
1.6 TDI - CR, 2010 Polo Sedan
Okay, what could really be causing the issues?

By the way, my car does not have a DPF. Does that change anything about the EGR valve's condition?
 
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