Noticed last night it was a little passed normal and when test driving today it was again. Expansion tank is full, upper hose is warm. I don't have an IR gun to try n get surface temp by the thermostat housing. I am going to try n get it into the shop soon but don't wanna make it worse by still driving it.
How hot is too hot on the stock gauge
- Thread starter John Z
- Start date
Napalm00
Technical Excellence Contributor
Seems fine to me? Stock gauge sucks ass but you are nowhere near hot if you can touch the hose. Any vehicle will smell like sweet coolant/fresh rubber and the hoses will scold you if it near overheating.
Ir thermometer is about $13 next day amazon prime fyi.
Ir thermometer is about $13 next day amazon prime fyi.
I wasn't sure, I just know it's a bit passed where it normally sat. I wasn't sure if it was one of those once it goes passed middle it already blew up kind of things. I'm going to look in to proper gauges, I just don't know if I wanna get a stock style vdo or the madman ems3.
That’s too hot, but it could also very well be a poor ground. If it is actually running hot I would suspect the thermostat on a 300 Tdi based on my experiences
So I kinda figured out some of my issue. I have to find the cause.
I noticed that when I hit bumps or have clutch shutter my parking and headlights flicker, and when that happens the temp gauge goes up. So last time my temp was high, I pulled over check the thermostat housing with IR gun, got 173°F. I turned the truck off n back on the temp was fine. Did this again when the gauge was high, just turned off n on and it went back to normal range.
I think I'm looking at a bad ground. So I checked my battery terminal, looked good. I have to check where the cable terminates to. I did read while searching someone else had an issue like this and found that it was a lose wire by the alternator housing.
I noticed that when I hit bumps or have clutch shutter my parking and headlights flicker, and when that happens the temp gauge goes up. So last time my temp was high, I pulled over check the thermostat housing with IR gun, got 173°F. I turned the truck off n back on the temp was fine. Did this again when the gauge was high, just turned off n on and it went back to normal range.
I think I'm looking at a bad ground. So I checked my battery terminal, looked good. I have to check where the cable terminates to. I did read while searching someone else had an issue like this and found that it was a lose wire by the alternator housing.
It’s probably the ground for the gauge. I bolt the instrument cluster and there will be a ground eyelet on the back of the coolant temp gauge. Makes sure it’s clean and tight
Isn't the ground the actual engine tho? It's a single wire to the coolant sensorz. So it would be a hot to the gauge, then it returns to ground thru the sensor on the engine?
The engine is the ground for the sensor, but the gauge has its own ground. Usually when that ground is loose the temp gauge will go up with the lights on
This makes more sense then. The electrical diagrams are tough to go through. So the ground I was looking at this morning was not it by the heater core. Where is the one I'm looking for then? I'm going to guess by the cluster somewhere
They are usually loose because the nut that holds the ground onto the gauge is just a round finger nut, not a nut you can put a wrench on
1of40
Well-known member
To me, until proven otherwise, the gauge seems to be doing its job. Buying one with numbers on it really doesn’t solve the root problem IMO. When this started on mine I bought an IR gun for $20 and noted what the temp was at tstat as the gauge started to move. For a week I check and rechecked and the deviation was immaterial. The gauge is likely telling you you have an issue with your cooling system that needs attention. My issue, the first time, was a water pump. Second time it was the radiator. The third time it was the water pump. The fourth time it was the tstat. These are really basic components that give up the ghost over time. What hasn’t failed yet is the shitty gauge.
