Maybe that could help quantify if a chick was hot or not.

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1980 300TD-China Blue/Blue MBTex-2nd Owner, 107K (Alt Blau) OBK #15
'06 Chevy Tahoe Z71 (for the wife & 4 kids, current mule) '03 Honda Odyssey (son #1's ride, reluctantly) '99 GMC Suburban (255K+ miles, semi-retired mule) 21' SeaRay Seville (summer escape pod)

I travel to CT every week........through New Haven.

In fact, the IR gun is currently in Newington. So, I can bring it down to you next week in the evening, if you want.

I met with forum member Funola yesterday evening and got a few quick temperature readings off the car.

From this initial assessment it appears that the temp gauge on the dash is reading about 10 C too high (~ 98 C on the dash vs 87 C shot on the head at the temp sensor). I will need to follow up to confirm this (immerse the grounded sensor in a beaker of coolant on a hot plate next to a 20-110 C glass thermometer), but it is very encouraging data.

Thanks again to Funola. I really appreciate you taking your time to lend a hand.

So I removed the temperature sensor from the head, left it connected, wrapped some wire around it to ground it and immersed it in 90 C liquid next to a thermometer from the lab. The dash gauge readings are right on (maybe even a degree or two too low).

At least I eliminated one part from the replacement list.

Funola: either we weren't using it right or your thermometer is not accurate.

Weren't you measuring the block temperature and not the coolant temperature. Is there reason to think they would be identical?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Doug, you work fast!

IR thermometers are tricky to use. You can get varied results depending on the angle you point at thr object being measured. A black object gives a more accurate reading than a white object.

When you took the sender out did coolant come out? I am not surprised your lab measurements were higher than the IR thermmometer. The tip of the sender while in the engine is likely hotter than the exterior of the sender and surrounding area.
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Maybe you should take up Brian's offer and try his IR thermometer? Let me know when and I can bring mine and we'll see if they read differently. Mine is a $40 Radio Shack unit. I did point it at a pot of boiling water when I first bought it and it was within a degree of 212 F.

btw did you have the sender hooked to the dash temp gauge in the car when you did the meausrement with a pot of hot liquid?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Kerry,

Yes and No, in that order. I am suspicious that the there would be such a large difference (10 C) between the coolant temp and the block temp aimed at the temp sensor. Others have posted IR thermometer results in much closer agreement with the dash gauge.

Funola,

I shot the area around the temp sensor at least a dozen times from different angles. The temp readings didn't seem to vary that much. I went with the highest temp reading.

I lost a pint or two of coolant when I pulled the temp sensor. If you drive it up to operating temp first you can drain the block through the radiator enough to avoid that particular mess.

I already PMed Brian.

Yes, I had the temp sensor connected (as it is normally) when I tested it. I just wrapped some bare wire around the threads and clipped it to the engine to ground it. The wire makes for a very short "leash" to maneuver. I ended up filling a coffee cup with boiling water as my "test vessel". I also waited a minute or two to let the sensor equilibrate.

FWIW I took an IR temp reading of the head today after 20 min of 65 mph on the hwy and pulled over to shoot it. Ambiebt temp was about 94F. Head temp at the middle glow plug right above the coolant temp sender was 194F per IR thermometer. Coolant temp gauge was indicating 90C which is exactly 194F. I will take out the temp sender next and immerse in boiling water with a thermometer as Doug has done and report back when I have results.

Doug, let me know if you want to borrow the IRT again. I can leave it with you this time till you are done.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked