ALH running hotter than before, but steady?

guillaumeber

Vendor
Joined
Aug 26, 2012
Location
Canada
TDI
Jetta 2000 TDI
I've got a concern since a couple months.

My scanguage2 has been displaying me, for about 4-5 years, that my engine was running between 86 C and 88 C, even in hot summer. This seemed normal to me.

Since a couple months, started at the end of the winter, it can be sometimes at about 88 but most of the time, I get a steady 92-93 C which seems a bit hot to me, however, it seems steady there and never went over 93 C.

What would be the best diagnostics? My coolant temperature sensor could be faulty or my thermostat, or my radiator getting clogged....anything else?

I could try reading the resistance on my coolant T sensor but where can I get the specs I should get?

Other tests I should make?
would you consider 93C too hot too?


thanks !

g.b.
 

JDSwan87

Black Swamp Thing
Joined
Feb 9, 2014
Location
Michigan near Toledo
TDI
2001 Jetta TDI, 5 speed Lagoon Blue Metallic(sold); 2005 Jetta TDI Wagon auto
I've got a concern since a couple months.
My scanguage2 has been displaying me, for about 4-5 years, that my engine was running between 86 C and 88 C, even in hot summer. This seemed normal to me.
Since a couple months, started at the end of the winter, it can be sometimes at about 88 but most of the time, I get a steady 92-93 C which seems a bit hot to me, however, it seems steady there and never went over 93 C.
What would be the best diagnostics? My coolant temperature sensor could be faulty or my thermostat, or my radiator getting clogged....anything else?
I could try reading the resistance on my coolant T sensor but where can I get the specs I should get?
Other tests I should make?
would you consider 93C too hot too?
thanks !
g.b.
First I would make sure your fans are running when they are supposed to. After that, look at the tstat. However, if it were mine and the fans worked as they should, I wouldn't worry about it. It's 2C different, it's not a space shuttle... now if it were 10c different, I would dig deeper.
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
93C won't hurt anything about the engine, but it will make plastic, rubber, and foam components under the hood fail sooner than they otherwise would.
 

VChristian

Veteran Member
Joined
May 20, 2006
Location
Western NY
TDI
99.5 Jetta, (2) 02 Jetta, 03 Jetta, 15 Jetta
My experience a low temp or high temp thermostat is one which is ready to fail. Having it fail high in the summer would be a pain.

I verify the temp with a passive infrared thermometer, and then I would put a new one in. Don't get a cheap one. I had to do a cylinderhead once because the thermostat, a name brand, failed, blocking the intake of the water pump on a VW diesel.

For the ALH, spend the $4 and have a new flange on hand. The thermostat replacement is fairly simple to do, and easy to get to.
 

snakeye

Veteran Member
Joined
Dec 13, 2009
Location
Montreal, Canada
TDI
2003 Jetta and Wagon, GLS 5sp
93C won't hurt anything about the engine, but it will make plastic, rubber, and foam components under the hood fail sooner than they otherwise would.
I highly doubt that.

Last time I checked my temp with vcds it was 97°C. New thermostat, fans work... I think my coolant sensor is bad. Actually I know it's bad. Had to unplug it all winter. I'd check that if I were you.
 

guillaumeber

Vendor
Joined
Aug 26, 2012
Location
Canada
TDI
Jetta 2000 TDI
Thanks for the inputs.

Coolant is super clean and about 1.5 years old. Oem VW stuff. I wouldn't suspect it first. I will be checking the temperature sensor and fans too. Any ''How to'' about those? Anybody knows the resistance I should be looking for on the coolant sensor?

I may also be replacing the T-stat soon. It's about 4 years old so who knows...

yesterday, During a 2 hours trip, the temperature fluctuated a lot between 87 and 95. 95 is starting to scare me a bit so I'll have to look trough it.

thanks again

g.b.
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
I highly doubt that.
Last time I checked my temp with vcds it was 97°C. New thermostat, fans work... I think my coolant sensor is bad. Actually I know it's bad. Had to unplug it all winter. I'd check that if I were you.
Proved it on my car. Every stinking piece of plastic under the hood started failing soon after installing a hotter t-stat. It's just simple physics: things age more quickly at elevated temperatures.
 

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
OP, does your lower radiator hose get hot at those higher temperatures? I have an OEM t-stat and, due to age, the wiring and dip stick tube have become brittle over the years.
 

snakeye

Veteran Member
Joined
Dec 13, 2009
Location
Montreal, Canada
TDI
2003 Jetta and Wagon, GLS 5sp
Proved it on my car. Every stinking piece of plastic under the hood started failing soon after installing a hotter t-stat. It's just simple physics: things age more quickly at elevated temperatures.
What temperature was your engine running at? I highly doubt 5°C of more will start destroying an engine.
 

wonneber

Top Post Dawg
Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
Anybody knows the resistance I should be looking for on the coolant sensor?
The resistance varies with temperature.

First thing in the morning scan the car and see if the CTS is about the same as the outside temp.

Same for the fuel temp.
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
What temperature was your engine running at? I highly doubt 5°C of more will start destroying an engine.
Who made claims of destroying engines? I simply said that the plastic and rubber components will fail at a faster rate. I was running a nominally rated 92C t-stat--but which actually ran 94-97C.
 

guillaumeber

Vendor
Joined
Aug 26, 2012
Location
Canada
TDI
Jetta 2000 TDI
I will be checking for the lower coolant hose. Does is beeing hot mean anything?

I'll also be checking VCDS for temps in the morning

thanks again!
 

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
A warm lower hose would indicate to me that the t-stat is functioning. I think it is more of an analog type thing.
 

snakeye

Veteran Member
Joined
Dec 13, 2009
Location
Montreal, Canada
TDI
2003 Jetta and Wagon, GLS 5sp
Who made claims of destroying engines? I simply said that the plastic and rubber components will fail at a faster rate. I was running a nominally rated 92C t-stat--but which actually ran 94-97C.
There's plastic in the head. I'm pretty sure if every stinkin piece of plastic under the hood starts falling, then you have a destroyed engine. I'm sure that's not what you meant, though. Still curious what kind of pieces failed exactly. And yes 97 is starting to be on the hot side for sure.
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
There's plastic in the head. I'm pretty sure if every stinkin piece of plastic under the hood starts falling, then you have a destroyed engine. I'm sure that's not what you meant, though. Still curious what kind of pieces failed exactly. And yes 97 is starting to be on the hot side for sure.

I don't remember; it's been years. All I know is that whatever money you save in fuel will be more than offset by extra parts under the hood. It's your car, so do what you want.
 
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