So. I'd like to make sure that my temp gauge is giving accurate information to me, because it's reading awfully hot. To make sure that it's properly calibrated, I need to take the temperature myself and compare the known temp with the temp gauge's reading. It was recommended that I "shoot the block."

I got a hold of an IR thermometer, but need help aiming it. I check the temp at the sender and on one side of it (on the big, brass bolt) I shoot 15ºC higher than the other side of it. The block, as you can imagine, gives me pretty wildly different temperature readings - from about 75º to about 110º.

So what's the area I'm interested in? Where's the place whose temperature reading that I can trust?

¡Gracias!

__________________
---
Cam
1982 240d

I'm no expert but the head is where the maximum heat is I would think. so I would shoot near the injector on the head. The exit cooling hose from block to radiator would be a good indicator too.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

In my experience those IR thermometers are picky about the surface to shoot it at. So don't compare a dull dirty spot to a shiny one, you'll get different readings.

__________________

I shoot the temp sender base on the sender near the head..
I figure that's the closest to indicated temp location I'm gonna get.
I also shoot the thermostat housing, but it's temp is difficult due to the reflective properties of the aluminum.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Uhh...I thought you were supposed to shoot the top radiator hose?

Have you considered buying a $25 radiator cap that has a thermometer built into it?

http://www.summitracing.com/search/brand/Mr-Gasket/Product-Line/Mr-Gasket-Thermocap-Radiator-Caps/?autoview=SKU

Does the 240D use a radiator cap or a remote degas bottle like the 300SD? If it's the remote bottle, the temp there will be quite different.

I agree with the comment on the IR Thermometer. They are not as accurate; but are good for a cursory check.

__________________
84 300D, 82 Volvo 244Gl Diesel

I've shot the thermostat housing and had pretty good results. A good IR thermometer will allow you to change the emissivity of the surface you are shooting. Although I found that changing it doesn't vary the results by that much.

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)