Do any of you have this Diesel Giant modification? I've been reading that the new 80c thermostats actually don't open up until 90c and that would keep the car's temp around 95c and 100c. Is this true? If so, would drilling these holes help keep the temps down around 80c to 85c? Is it better to install a 70c thermo?

I still need to do a flush. I'm gonna have to take it somewhere to be done. I can't work with that much liquid on the street (I live in brooklyn, ny). I want to be able to hand the mechanic a modified thermostat to install while he's in there if need be.

Attached Thumbnails

 

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1984 300td euro turbo

The bypass thermostat does not "open" at some precise temperature. It actuates progressively over a temperature range.

The 617 turbo engine has a thermostat bypass passage already, built into the thermostat housing.

If you have had overheating problems, there is a good chance you have a pressure leak. A pressure test of the cooling system might be more helpful than drilling holes in the thermostat.

"Monkeying Around" with a Mercedes Thermostat (A La D.G.) is not a solution
to your Problem (Or anyone else's).

Mercedes Cooling Systems are Very,Very Complex and not to be "Altered".
[Certainly not by the Instructions of Some Self Appointed Internet Barnum]

The Problem is not the Thermostat's Design ,although you may very well have
a BAD Thermostat.

'Find out the Real Problem and Fix it.

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'84 300SD sold
124.128

I've never put holes in any of the thermostats I've used. Usually modifying a new part is not needed. If Mercedes thought the t-stat needed holes they would have made them that way. If you are overheating(or not heating enough) and have a good t-stat and coolant than something else is wrong. Drilling hole in the t-stat is just masking other problems.

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I have no need to do it on my Mercedes but I have owned 2 vehicles that if you refilled the coolant would trap Air behind the Thermostat.
I drilled 1 no bigger than 1/8" just so that the Air would pass I could fill with Coolant without the burping issue. I did not do it to solve any overheating problem.

I also used to Test Thermostats before I put in a new one.
After changing Head Gaskets on my Van I could not find the original good Thermostat and bought another one. I did not test it. And, sure enough I paid for that.
I stopped the Engine just as the temp was approching the Red Zone.

Had to remove the Thermstat and test it and and sure enough opening 10-12 degrees late (the stock Thermometer tem is 190 degrees F so opening 10+ degrees late makes a puts it on the edge of overheating).

Suspend the Thermostat off the bottom of a pot of water (with a tsp of Salt disolve in it so it does not bubble so much). Put a Thermometer in the water (Candy or Meat thermometers work) as the temp builds up watch when the Thermostat begins to open and note if it opens fully or not.
I am OK if it is within 5 degrees of what it is supposed to be. 10 or more degrees is too much.
Because I did not test the new Thermostat I cost Myself a lot of extra labor and mess of having to Drain the Coolant and refill it again.

Another Note: When I returned it the Counter Guy tried to sell me a lower temp than Stock Thermostat. He could not get the idea that if I was overheating with what is supposed to be the correct temp Thermostat that I should fix what was causing the overheating.

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84 300D, 82 Volvo 244Gl Diesel

I agree. there is no benefit at all with a bypass thermostat system such as a benz has to drilling holes.

On my Formula Ford race car which has a 1.6 pushrod Kent motor, I installed a thermostat and drilled two small holes which will bleed a little coolant at all times to prevent hot spots. ON that engine it is a traditional american style on off thermostat....not a bypass stat.

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[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.

I tried the Thermostat Mod you are inquiring about on my 83 SD and it runs ~80C now instead of 90-100. Some will say thats not healthy for the engine. My car runs great but diesels love heat. One set back is it takes longer to heat in the winter so I block off the radiator.

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I LOVE CATS....AND FRIES

1981 300sd
1983 300sd
1985 300d
1983 300cd
1991 350sdl

My 300D had lots of "stupid little" cooling problems when I picked it up. Most of the problems came from alterations to the factory cooling system by the previous owner.

I replaced a bunch of components with the factory parts and the system now performs flawlessly. Even on the hottest days with the A/C on I have no issues at all and the temp. never rises above 85C. I have verified this with an infrared thermometer.

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AJ

1985 300D (SOLD)

Get ahold of a Infrared Thermometer, and do some shooting around the engine when it is up to temp. this way you can see if it really is over heating. shoot it where the temp sender screws into the block.

the temp sender could be faulty giving a wrong reading, or the temp gauge could be reading wrong also.

Make sure the radiator isn`t particially blocked with debris/bugs or bent fins. there can be a blockage between the AC condensor and the radiator with debris.



I was having my new metric Motor engine running hot, or it seemed to. I replaced the radiator with a new Behr along with the engine so i was starting with a clean cooling system.
I swapped the wires between the temp senders, replaced the sender. thought maybe the gauge was a problem and changed it. then swapped in a gauge that reads in "F" and not "C". (Iam an American and not a forigner and understand "F" readings) and still running warmer. even had the front end higher to burp the cooling system. then read a thermostat used in the SLC/SL is a 75C and stuck one in. seemed to help. then got a IR temp lazer pointer to see what the engine was really running. nothing was out of line, so I don`t worry about it now and just drive it. gauge sits around 180deg or a little higher.

Iam not too sure I would drill the holes in the Thermostat either for a long term thing, maybe in a emergency situation, then just fix the problem.

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

drilling holes in a bypass stat will solve nothing. nothing.

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[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.

So the thremostat on a Benz is a "bypass stat"? Could you explain that further?

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My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

ON my Kent engine the stat is an on off valve like your hose bib on the side of your house. Open or closed.

A bypass stat is more like a switch in a train track. When the engine is cold the water is run from the pump back to the head and through the block. As it gets warm the switch gradually opens and diverts the water to the radiator. Once fully hot the stat may divert all of the water to the rad.

The purpose is to keep the engine parts all the same temp with no hot spots.

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[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.

The route (cold) is from the pump, through the block, through the head, then back to the pump.

'splained...

A portion of the coolant no longer "bypasses" the radiator. It goes from the head to the radiator. Look at the legend and the arrows. The path from D to C is closed by the thermostat above about 94c.

Attached Files

bypass thermostat.pdf (141.9 KB, 260 views)

What is it with this obsession about DG ? Is he some Einstein of all things diesel?
The ideas raised on here from the site often are at best questionable.
Reluctantly, MB will always make good their short comings. There has not been a recall to drill extra holes in thermostats.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving