240D Is getting warm
 

My 1983 240D has been running a bit hotter than I like lately. Today I had the needle go above the 100c mark, and I usually like to see it between the 80 and 100 marks. I did a cooling flush, but it didn't help really. As I noted in another post, I have the solid mount fan, so the clutch problem would not come into this. It does have air conditioning but I do not use it. I was just wondering if any of you had any ideas.

Thanks,
Nitro

Recently installed new water pump in my 240D.... the old pump was not entirely shot, but cast iron blades were eroded into nubs.

Valvoline has 2 types of coolant flush.... one 10 minute flush and the other you use for 6 or more hours. I've had good luck with the 6 hour flush.

thermostat would be one culprit to check, try taking it out and testing it

Thanks Maxwell, you reminded me I've been driving without a thermostat since replacing the water pump and flushing the system in July.

That's another thing you can do..... discard the thermostat entirely during Summer months.

Taking out the thermostat would be fine if the only purpose it served was keeping the engine cool.. but it is also supposed to get the engine up to operating temperature as fast as possible... since most wear happens between startup and that time....

240DieselDog,

Run without the thermostst in the summer? Show me where it says that in the MB manual and I will do it. Otherwise I will leave my themostat where it belongs, in the engine. Once the engine temp is above the opening of a properly functioning thermostat, the thermostat has little effect on the engine temperature.

For summer overheating, I would take the radiator to a radiator shop for flow testing and profesional cleaning.

Although running at temperatures above 100C may seem hot to us, its not hot to an engine. They are designed to run hot. As long as the coolant doesn't boil, an engine won't be damaged buy running hot. Look where the red mark is on the temperature gage. As long as temp stays below red mark in hot weather or up long hills, engine won't be damaged.



P E H

"discard the thermostat entirely during Summer months."

running w/o the thermostat will cause the engine run HOTTER because MB uses a bypass system and the coolant will BYPASS the radiator if the thermostat is removed.:eek:

For me this has been Summertime SOP for years and years:

1)Remove thermostat..... 2) Flush the cooling system 2 or 3 times, finally running 95% straight water with just a little coolant to prevent rust....... 3)Install thermostat and add coolant in the Fall.

*footnote: the most effective way to flush cooling system is to remove thermostat first.

Haiges - MB manual is not gospel.... For example, they've got that idiot fan shroud that should be ripped right out of every car - No, it doesnt make the car run cooler for its being there.... yet it discourages ordinary maintenance and repair, creating huge hassle (just in case someone is stupid enough to jam their hands into fan blades)...... Also, just for grins, ask your dealership about putting a trailer hitch on the 4-spd. 240D. They will crap in their pants!! Sorry, but the MB manual is not the gospel.

Quote: "As long as the coolant doesn't boil, an engine won't be damaged buy running hot. Look where the red mark is on the temperature gage. "

This may be OK for you, but not for me.... aint never gonna get even close to overheating my engine - and i think on anyone who DOES overheat an engine as being incompetent for not watching the guage and not taking preventive/maintenance measures first.

Stevo - If your theory is correct, then logically a fully open thermostat also prevents the radiator from getting any water. If anything I'd expect the opposite to be true - whereby closed thermostat cuts off the radiator, channeling water through the engine instead. I dunno much about the radiator bypass system, maybe you can explain it.

Experience teaches me the '79 240D runs cool as cucumber at/near 175* without thermostat after effective coolant system flush. And warmup time is not outrageously lengthened either.

On my sailboat, the bypass cooling system allows the waterpump to circulate water without passing thru the engine block until the engine gets up to temperature. At that point, the thermostat opens and blocks the loop that bypasses the block, forcing the coolant to circulate thru the block.

I'd be curious to see a diagram of the operations of an MB cooling system since it is not clear to me exactly what is happening.

Replace the 240D radiator with one from a nat. asp. 300D. I did 1.5 years ago and the temp never gets above 195. The radiator drops right in and you can still use the 240D hoses.

Have no clue where you got this idea
 

"they've got that idiot fan shroud that should be ripped right out of every car - No, it doesnt make the car run cooler for its being there.... "

Sorry , you are completely off on that one... air works like any fluid.... and follows the path of least resistance... and the path of least resistance is NOT THROUGH THE RADIATOR... which is where you need to air to go...
If that shroud is not there the air will be sucked up from under the car and blown across the engine... and if you are at a stop it will then be RE SUCKED UP and blown across it again...

I hope everyone will leave their shroud IN PLACE...

What should have happened.. was MB and all other car makers should have made the shroud in two pieces,,, and easily removable...

Wow...I have started quite the cooling war! I think I might have to try the 300D radiator route, that sounds like a viable alternative to me. It's either the rad. or the H20 pump because I replaced the thermo a few months ago.

Thanks for the advice guys

240DieselDog

Check your PMs, I sent you the diagrams from the service manual which should explain how the system works. I haven't time now to try and figure out how to post it. I have never run w/o the T stat or the fan shroud but if it works for you, what can I say. Here is something that should not work but worked for me... My "79' 240d was overheating last year and I drilled a small hole in the round flat part of the T stat that closes over the bypass line and the car ran cooler. Logic say that should not work but it did.

Steve

I don't know why you are surprised that helped.. Sube for instance has a small hole in the Tstat.. and SPECIFIES it be installed with that hole UP...

'Sube for instance " Whats that?? What I'm talking about is the part that closes over the bypass, the round part that is below the main body of the T stat.

Steve

Before tearing into the cooling system. Get a laser thermometer and check the radiator. I've found mine to be partially plugged, and will be replacing it. With the needle at 105c on the guage, the thermometer was showing 110 - 115f across most of the front, and around 140 - 150f on the back. The tech that I was watching use this was also able to verify that the water pump was indeed circulating, and that the thermostat was opening by checking temperature all along the engine and external plumbing. It's a neat tool that will be added to my selection very soon.

Subaru....
"the round part that is below the main body of the T stat.
" You mean on the ' flat' ? or something else?

Greg

Ya, Sorry, I dont know how to describe it but you have the "main" part of the T stat that controls the main flow , then theres that flat round (1 inch dia +-) thin "plate" that covers the bypass hole. Drill a small hole in that.

Subaru....Oh. my daughter wants one, although she loves her 240d a Sub would more fit her needs, I was crushed at first
:eek: but i got over it :cool:
Steve

yes, a little hole there can really help....

"My "79' 240d was overheating last year and I drilled a small hole in the round flat part of the T stat..."

Stevo, thanks that sounds like good advice.... also way to eliminate air pocket from forming with hole pointing up. Will do this when installing T-stat after weather cools down.

Another thing I'd like to do is mainline auxilliary fan to toggle switch on console. Am also wondering if 300D or 280E radiator would hold more water. Running hot seems to be mostly 240D problem... not surprising as this car taxes its engine to the max.

Meanwhile my '79 240D stays mostly in the numbers "175" on the guage with no thermostat and no shroud.

Leatherman, your idea of shroud helping airflow when standing still makes sense..... however, it strikes me the bloody shroud actually blocks airflow when car is moving.

The damned shroud came into being at/near 1973 when they also deflated the seats on account of 'fire hazard' from flamable glue holding horsehairs together. I'm glad to be rid of it, so maintainance can be done easily - important stuff like flushing the system, checking the belts, etc.

You know me, I've got no patience for wacky over-engineered features..... and I can recite laundry list of useless items attached to an otherwise superb automobile - stuff like the idiot climate control, feeble cruise control, stupid 'engine management' systems, sensors and relays.

When I rebuilt the engine for my "79' 240d I put in a new 300D radiator.

240DieselDog Did that diagram come through?

Steve

"Leatherman, your idea of shroud helping airflow when standing still makes sense..... however, it strikes me the bloody shroud actually blocks airflow when car is moving. "

That is very close... The shroud is not at fault though... the fan , when turning at certain rpms,but with the car speed above certain speeds , does act as a restriction to airflow.
However, the amount of air which does cross the radiator fins should still be fine for cooling the engine even though some may be blocked outside the car and go around the radiator.
This situation is why some cars went to ONLY electric fans... and some added the viscous clutch to allow the ram air going through the radiator to push the fan past the rpm which it would have been turning due to the belt run by the engine.
If you will check out some professionals who know about air pressure you will find that the area under the front of the car, when it is moving , is a high pressure area... which means without the shroud you have air pressure in the engine area which will also be working against air going through the radiator fins...
I hope you will reconsider your decision to run your car without the shroud.

If you look around...you will find that MB is not the only company using shrouds... so it may not be " overengineering"... it may be a good design based on sound air flow concepts.
It is even more critical to have the shroud if you have an AC condensor because that adds even more restrictions to air getting to the radiator.

Stevo, nope havent gotten the diagram..... why dont you post it here? It cant be any tougher to post on msg.brd... I'd like to see how the waterflow bypass system works. How much larger is the 300D radiator?? Chart of total coolant capacity says 10.5 qts. (240D) - 11.7 qts. (300D) - so it might be less than 1 pint larger, i dunno.

Leatherman, post '73 radiator shroud (standard feature on all cars) strikes me as safety device to prevent everybody from getting their fingers chopped off. It emerged about the same time they started telling crybabies NEVER to remove radiator cap when warmed up engine is idling - another myth that can be ignored by someone who knows what they're doing..... In fact you risk cracking the head by adding water, even little at a time, when the engine is NOT idling.

Without the shroud - I'm happy having full access to front engine components. Otherwise, I'd be removing and installing the bloody thing several times each year just to maintain the car..... removing thermostat for coolant flush, turning crankshaft for valve adjustment, tightening the belts, etc.

Bottom line, flushing the system twice a year with $3.99 valvoline 6 hour radiator cleaner probably does more good than all the shrouds in the world.

Btw, from what you say about air flow.... it sounds like front end spoiler would also make the 240D run cooler, but is this effect actually measureable?

240DieselDog,

Think of the shroud as a duct. It is not a safety device, and became a standard part once air conditioning became a popular option. With the added flow resistance of the condenser in line with the radiator, it became necessary to block the air flow "short circuits" that were possible without it.

I posted these excerpts from the shop manual I have for my 240D:

Here is a systme schematic showing the engine fully warmed up and under full load:

Here is a view of the system during warm-up from a cold start, showing only the area right around the thermostat:

Here is a view with the system in its normal operating mode when the thermostat balances by-pass flow and flow through the radiator to regulate engine coolant temperature:

240DieselDog,

So, the coolant system design suffers a loss of capacity when you take the thermostat out, as noted above. And the shroud is really a duct that ensures the energy being consumed to drive the engine fan actually makes the air go through the radiator and remove heat from the coolant circulating in the engine. And, in spite of what you have done to your car, it still runs within the normal operating temperature range. I think your treatments must be keeping the rest of the system operating at peak performance, which is adequate for the engine to keep its cool.

All this goes to show that from the factory these cars had excess capacity. I have noted in the past they always run at a dead 175*F, or just under 80*C no matter what the outside conditions, speed, slope of the road, etc when they are new. The fact that this changes means somewhere capacity has been lost. I am aware of the manual bold letters above saying it is ok to run just under 120*C, but I grow nervous when I see the needle on the gage off its previous invisible rest or peg. I think another good flush is in order on my 240D.

The other cars, gas powered units and my E300D TurboDiesel, have always been a little easier to get to run over the 80*C mark in stop and go traffic, especially in the summer.

Hope this helps, Jim

Thank you Jim..I have company visiting and dont have time to mess with figuring out how to do anything new right now, thats just what I tried to send him.
Steve

Outstanding!!! fig.3 (partial load) most closely resembles operation without thermostat.

As it stands with system wide open, combined with new water pump.... the needle hardly ever leaves the 175* range.

Old water pump seal was not shot..... but blades were eroded down to nubs. This tells me water pump efficiency can fade away unnoticed. Replaced the WP in July when the needle climbed 3/4 to redline on rare occasions. Discarded T-stat might have been shot too, have a new one in the trunk.

Had no idea the bypass plate closed under heavy load to mainline engine coolant to the radiator. This might have hurt me if mountains were nearby. I always thought it just cut off engine coolant when closed, otherwise it opened all channels.

Jim, you made a believer out of me!

Nevertheless, can understand how pulling the T-stat increases efficiency of coolant flush that I've been doing twice each year, running 95% staight H2O in Summer months, better than anti-freeze for cooling the engine.

Next month I'll pull the radiator and spray out cooling fins with garden hose and soap to atone for my errors. The shroud?? .....nah, its still a nuisance device to me. Am still suspicious of it blocking airflow at high speeds.

Dont judge me too harshly - i grew up owning primitive finbodies back in the '80s that had none of these issues.

Thanks for taking time to post the coolant flow chart - something for everybody who searches "Thermostat"...... immortalized in archives that will never be lost or forgotten.

:rolleyes:

Hi Nitro.

Your MB dealer sells some sort of flush(asorbic acid?)
They don't stock it,you need to ask them to order it.

Flush the system.
Then refill with MB coolant(has lubrication in it to
prevent corrosion).
Add waterwetter to the coolant(it reduces the temp
by almost 30*F).(claimed???)


240Dieseldog.

You receive the most airflow when driving and as
long as the engine temp doesn't go to high the
fan clutch doesn't engage.
But when stopped at a T-light the engine temp
will rise,activating the clutch and increasing the
airflow over the radiator.
When you remove the shroud the airflow is dispersed
over the hole engine bay.
The shroud funnels the air over the radiator to
cool the coolant,thus reducing the engine temp.

Hope this helps.

Louis.

My understanding of the fan clutch is that it enables the fan to actually spin faster than crankshaft speed. The fan clutch froze on my 280/8 - causing the car to run hotter.

Ther aint no fan clutch on the 240D..... therefore radiator air flow is restricted by the shroud and limited by fan speed.

No doubt the shroud is good idea when standing still, but you probably get better air flow through the radiator without it when traveling at speed.

Tie breaker for me is fan shroud discourages maintenance/repair of the engine...... stuff like flushing the system twice a year - mainlining coolant flush without the thermostat.

Well I guess "the proof is in the pudding" If your 240D runs cool under load in traffic and up hills. Then maybe the shroud is indeed something that could be done away with. Keep us posted
This is something like the oil coolers on 240Ds. They are not installed on the 240ds NOT exported. My euro 240D did not have one and when I rebuilt the "80" engine for my "79" I dispensed with it. Why have something thats expensive to replace and a potential big problem? If Leathermang can get away with it in Texas....well..there you go. :cool:

240DieselDog.... concerning your statement "therefore radiator air flow is restricted by the shroud and limited by fan speed. "

In the most narrow sense, and only taking into account ONE VARIABLE, yes that statement is correct.

However, you have left out the fact that at speed the ram air effect increases the pressure on the upstream side of the condensor/radiator ... and are ignoring the need for it at lower speeds....

At that speed, which is very high, that you MIGHT be exceeding the air flow with only ram air... and thus have some restriction of the amount going through the shroud... you ARE STILL GETTING THE AIR WHICH THE FAN IS PULLING ( ALLOWING ) THROUGH THE SYSTEM... and since this amount exceeds the amount needed to keep the engine cool.... it is a MOOT/ point.

If you are really worried about it you could add an overrunning fan clutch... but you are really just introducing something which can go wrong at some time and unless its default condition when broken is a locked to the shaft condition since you do not need that extra air flow at the speeds we are talking about.

If you don't believe JimSmith -who in the world would you believe?

It looks like I am going to take the bait...thanks Greg

First, a fan being driven by the engine always improves air flow through the radiator (and condenser if you have A/C). It does this by lowering the air pressure behind the radiator, which makes the higher pressure air at the front side of the radiator flow through the radiator to the lower pressure area behind it. The radiator makes up about 90% of the resistance to air flow in the circuit. The belt driven fan makes no resistance in the circuit as it induces flow. The rest of the resistance is due to the cosmetic radiator grille in front of the real radiator, and the structural stuff that the car has going across this area.

The fact that the electric fan in the front is usually not "on" and plenty of air still makes it through the radiator should add some empirical validity to the statement if the concepts of rotating fan blades is confusing.

The genesis of fan clutches and shrouds can be traced to Corporate Average Fuel Economy (CAFE) standards and the universal installation of air conditioning. The fan draws a fixed amount of horsepower at idle. Since it is a turbo machine, it has a general relationship between speed and horsepower drawn that can be estimated using a cubic curve. This means if the engine idles at 600 rpm and draws some fixed horsepower, at 1200 rpm the horsepower needed for the fan to turn goes to 8 times the idle value. At 2400 rpm it is 64 times that value and at 3600 rpm it is 216 times that value.

Adding A/C typically demands more idle speed capacity of the fan, since the condenser adds flow resistance and, when the air conditioning is on, a heat load. So you need more differential pressure at idle, and you need more air, which means you need more fan.

As the engine speeds up, normally the car speeds up too, and the relative velocity of the car and the air causes a high pressure area to build up in front of the radiator. This adds to the differential pressure across the radiator and increases the airflow through the radiator. Eventually the car speed alone generates enough flow to handle the heat load. At these speeds the fan is no longer needed and if you could turn it off, you would save horsepower and consequently fuel.

It is likely a small number in terms of fuel savings for you, the individual, but it helps car companies with their CAFE numbers, which helps them sell more gas guzzlers. So electrically driven fans and fan clutches for those driven by a fan belt off the engine crankshaft were introduced. These clutches come in two general types, those that are on and off (electromagnetic clutches) and those that are on-off and speed limiting (viscous). The viscous ones limit speed when the torque demand to increase speed exceeds the torque transmission capacity of the clutch. At that point the clutch slips.

There is no way the air flow through the ratiator can increase the speed of the fan over the speed it is being driven by the engine, even on a viscous clutch in speed limiting mode. This is because the air coming through the radiator is being enhanced by the fan lowering the air pressure on the back side of the radiator.

The shroud improves the efficiency of the fan by preventing the air already behind the radiator from being sucked into the air stream without going through the radiator.

The fact that 240DieselDog's car works fine without the shroud is likely due, as I noted above, to the fact that in as new condition the car has a great deal of extra capacity, and the loss of the fan efficiency by removing the shroud is not critical. My personal experience is that when these cars are working correctly, the temperature never exceeds 78 or 79*C. That it is not harmful to the engine to operate at higher temps is probably true, but any time they go over the 80*C mark on the gage, something is no longer operating as it did, so it is not normal.

Also, while I am on this topic, the removal of the thermostat is not similar to the part load condition from a fluid flow perspective. If you take the thermostat out, the water pump discharge pressure will be nearly equal at the normal "goes into" line to the radiator and the "goes out of" line. In this condition there will be little or no flow through the radiator water way passages (no differential pressue to push the water through the radiator). Nearly all the flow will go the short circuit route and by-pass the radiator. I have yet to figure out why 240DieselDog's car works without the thermostat installed.

Well, I ended up writing this twice! I lost it the first time by switching screens to read something else and had to rewrite it. I hope this helps clear up what the design basis is for the system. Jim

Jim

Thanks for taking the time to explain that. I appreciate the help as I try to understand what makes there critters "tick" or NOT tick. :cool:

Steve

Woke up this thread to report I've had to put Thermostat back into the car today because with temp dropping near 60* engine was running too cold without it.... couldnt run hotter than below 175* - probably at 160.

With thermostat, the car now warms up quicker and runs just above 175* line. Have also drilled 1/16" hole in Tstat casing to prevent air pockets.

Why does the dieseldog's '79 240D run cooler without Thermostat in Summer months?

After studying Jim's pics of water flow above, can only suggest the Tstat blocks flow from radiator to water pump in some degree. They may have changed position of Thermostat housing from the '79 240D....... mine faces forward and mainlines water from radiator to water pump as path of least resistance.

Next Summer, I'll be doing the same thing - pulling Tstat, flushing the system, then running with straight unobstructed flow...... carrying Tstat in trunk.

Itsa 5 minute operation, removing/installing thermostat without the nuissance fan-shroud in the way.

Well, you guys must have jinxed my car with this little cooling war. I decided to drive the Euro to work today after it had been behaving for nearly two weeks worth of driving after replacing the radiator.

Well, the temp guage started travelling rapidly up and down between 85 and 110!! I ended up stopping at a 7-11 to buy some premix to add to the radiator thinking that I had an air pocket that happened to show itself this morning. Well, I checked the coolant level, and it was still full. I checked the lower hose, and it was stone cold. I pulled the hose to allow some coolant out, and added new to try to pass any air pockets. The car ran at a solid 85 the rest of the way to work. I checked the lower hose again upon arrival at work. It was still stone cold. :( I hunted down a thermostat for the car and took off on a break to pick it up. I then installed it during my lunch break and went to pick up some food afterwards (gotta love these cars for their simplicity). Now the damn thing is running solidly at 100 degrees for the short trip that it got. The lower hose is still cold to the touch. :( I ordered a water pump from Fastlane to install.