I have been noticing now that its warming up that if I turn my heat off or turn the dial off max heat that My temp creeps up to around 100. With heat on high it runs around 85. Can pretty much slowly move the climate temp selector and watch the temp rise and fall with temp selection. I have changed the thermostat already. I have a new water pump and plan on changing it out along with doing a flush using acid. Just wanted to see if anyone else had any input or other ideas. Possibly change thermostat again possible bad one. Thanks

1982 300D

Unfortunately it is now so common to get a bad thermostat, it's recommended to test new ones in hot water prior to the install. I learned this the hard way last year.

If you have access to an infrared thermometer gun, it doesn't hurt to shoot it at the thermostat housing to double check what the gauge is telling you.

The citric acid flush isn't as widely recommended as it once was. Many now advocate simply doing a thorough flush of the system.

How old is the radiator?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

That's a good thought about checking the gauge. Guess figured it is probably pretty accurate because of what it shows when heat is on high and driving and how it does change with temp selection. Most generally the temp fluctuation is very slow and steady changing. Every once in a while I will see the temp gauge bounce up or down. Radiator is original I believe. I bought the car with 172000 miles on it and have put around 6500 on it. Enjoy working on it.

The other thing, which I failed to mention, is to change the pressure cap on the expansion tank.

Your gauge is not likely completely inaccurate, mine is a couple of degrees high compared to the underhood reading. Just wanted to note it.

Maybe shop for a rad? These ones don't last forever (far from it).

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Hose out your radiator.
Remove the fan, blow it out in the opposite direction of air flow.

100 isn't bad. Some of the Powerstroke guys fit a warmer than stock thermostat for improved fuel economy and smoother running. Mine runs around 100 most of the time since I changed out the old stuck open thermostat several years ago. I'd just keep an eye on it for now. If it starts getting near 120 then you have a problem.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Do you still have the AC Condenser installed? If so then there could be debris that
accumulated between it and the Radiator.

Seeing the Temp Gauge bounce up or down, could be a ground problem.
I had a problem with the Gauge spiking to the max. then turning off the engine and restarting it, would show normal for a while then bounce and jump up again. Also the battery light would glow when driving or the engine turned off.

Changed the Gauge with a good one, changed the water temp sensor, had a new Bahr Radiator and new Thermostat, new Engine so this had me puzzled for a while.

Finally figured it out, it was the engine to body ground cable. There was paint on the engine side where it bolts down. scrapped it off and then it made a good contact, and all fixed.


Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

All of the above is pretty good.

I'll add pictorial evidence of what can happen in radiators and these blocks.

first pic is the attachment site for the aluminum water pump carrier. Yes, it is 95% clogged.

Attached Thumbnails

   

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Another benefit of running NPG- no corrosion.

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'83 300D, 126K miles.

Two questions: Does heat rise faster when the car is stopped or at speed?

If heat rises faster when the car is stopped, the problem is more likely to be airflow...fan clutch broken or debris caught in the radiator fins. As pointed out, debris gathers between the condenser and the radiator; it also gathers between the fan motor and the radiator.

If heat rises when the car is in motion, then the problem is going to be a clogged radiator. You can remove the radiator and bring it to a shop to be boiled out, but when a radiator is compromised enough to restrict flow, the best economy may be to just replace it.

100 isn't normal or desirable in this car. These cars were designed to run 80-85. If you're seeing more than a temporary excursion above this, it's a problem. NPG is flammable, and won't fix a clogged radiator.

sorry wrong thread

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

I think you're pursuing a solution to a problem that doesn't exist.

I'd like to point out that my 300D runs at about 100 (verified with an IR thermometer) and has for about the last eight years without a problem. My 240D did the same.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

If you're happy with that, then I can't help you. But it's not the way either car was intended to work.

X2

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

Thanks for all the info. I have verified the temp gauge is accurate. The temp only rises to 100 when I am driving over 60 mph or so normally anything under 60 it stays around 85-90. I plan on working on this next week cleaning out radiator and changing coolant and flushing system.