Could Use a Little Thought on a Problem

[Boomer]

After almost 47,770 miles of totally trouble free driving, my 2017 VW Alltrack has developed some weird symptoms. First off, let me say that no codes have been set and no lights have turned on. Problem...after a 100 mile drive last weekend, the car smelled really hot when I pulled into the garage. Upon opening the hood the front braces that run from the fenders to the front metal holding the radiator, intercooler an AC were very hot to the touch. I never saw that before. And overnight, there was a smell of gasoline in the garage. And to top it off, my mileage fell from about 35 to 31. It seems almost like the turbo may be putting hot exhaust into the compressed air side of things. The dealership went all over it but with no codes or lights said to continue to drive it. They could find no signs of any gasoline leakage at the engine or under the car.

Any thoughts on what might be going on here? I welcome all comments and thank responders for their time!!

 

[MRC01]

Do you notice any loss of power?
Did you drive it hard with WOT runs in low gears, then suddenly park it?
Any sign of coolant splash or leakage around the radiator or engine bay?
After it cools off, if you run your finger along the inside of the exhaust, is there any oil/moisture? There may be soot but it should be completely dry.

 

[DrDanger]

Maybe a faulty lambda sensor

 

[Ursatdx]

Use a cheap Harbor Freight infrared thermometer to look at wheel temps.
The gas smell is something I have no advice on.

 

[JHZR2]

Use a cheap Harbor Freight infrared thermometer to look at wheel temps.
The gas smell is something I have no advice on.

Agree or small IR camera.

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• JHZR2
• Mar 28, 2021

 

[Greasymechtech]

Any preventive maintenance for intake/valve deposits? toptier fuel used or regular FI cleaners for regular injector cleaning?

 

[zrxkawboy]

Sadly, many techs today won't/can't even attempt to diagnose a problem if no code is set.

 

[Blueshound]

My VW knowledge tapers off quickly after CIS injection unfortunately.
Just to rule it out, is there anything else in your garage that smell "hot" or leak gasoline? Lower mpg over 100 miles doesn't necessarily mean there's a problem. Maybe you don't have one.

 

[Cujet]

Not to worry about exhaust gasses going through the turbo and into the cold side. Any internal leak on a turbocharger will go into the crankcase, and will end up in the PCV system, and very rough operation.

We can guess at what might be happening, but I think the first thing I'd do is look on a vehicle specific forum and see if others have similar issues.

Can you view the coolant temp in real time? Was it out of range?

My first guess is bad gas, with a high ethanol content. If you can find a zero ethanol station, it's worth a try. I drive 3 different F150's. All of them hate any ethanol and MPG drops markedly. Today, with a batch of Costco gas, my truck was constantly downshifting in steady cruise on the highway. It never does that. The engine was struggling to make power. MPG with the V8 is 15-16 with non eth gas, and 12.1 with Costco fuel. Same trips, same speeds, same conditions.

 

[meep]

Radiator fans not running?

 

[Passport1]

If it seems hot and has a gasoline smell best to park it outside until you figure what is causing this.

 

[Boomer]

Soot in the tail pipes is dry. I have always used Top Tier (Exxon or Shell) and mostly 93 octane. Performance does not seem to be affected. Still runs hard when you hit it. I checked the wheels with my hands and they are normal temps. Both the coolant and oil temperatures are normal on the gauges when driving.

 

[Danno]

1st thought was catalytic convertor honeycomb partial collapse, increasing back pressure, causes increased fuel consumption and everything runs hotter.

 

[Greasymechtech]

Run an IVD cleaner. With 48k, I'd probably run 2 cans and a good soak after each run.

 

[Kira]

I'm with Danno re partially clogged exhaust part. Got vacuum readings?

Do you drive local, highway or mix?

 

[zzyzzx]

Use a cheap Harbor Freight infrared thermometer to look at wheel temps.

This is how I figured out that I had a stuck brake caliper. The OP should be checking their exhaust components with an IR thermometer as well.

 

[bobdoo]

Has turbo? Might be the first time it got heat soaked (mine used to glow red-hot after a speedier than normal drive).

High underhood temps, not enough airflow. Rad fans, does the grill have powered slats?

 

[Boomer]

Update... thought about the issue for a tiefter reading all the posts. Then it dawned on me that I might have an injector sticking open at times when the engine is shut off, allowing some fuel to dribble out and evaporate inside the hot engine and out the exhaust. So I ran a container of Techron through over 300 miles after adding it and it seems the gasoline odor is gone! The heat on the front braces seems to be due to the headlights that are placed right under them and are on whenever the car is running. I guess I just never noticed that before. Further updates if called for!