Guys,
I recently disabled the EGR on my 85 300SD by blocking vacuum hose with a ball bearing. I LOVE the results. Much improved shifting...especially first to second...smoooooth! Acceleration seems better also, but not as drastic as the shifting improvement. And, it appears mpg is going to get better (my goal in first place)...I’m over 200 miles a little less than half an tank. And to make things even better...there’s hardly any smoke, even on heavy acceleration!
So here’s the downside. My car runs hotter. Not overheating HOT (coolant reservior not even very warm to touch and level is same as always). Physically every thing seems the same. But the temp gauge used to hold steady at around 85C, on hot days it might creep up to 90C if a/c on in slow traffic. Now, after disabling EGR, it holds a bit around 92C to 95C, and after a “spirited” run in which I got it up to about 4600 rpm once or twice as I usually do, it ran up to just a hair over 100C while idling at end of freeway ramp. After the light changed and I started driving street speeds of about 30-40 mph, it went back to about 92C quickly. Now bear in mind on that day it was about 68F outside (I’m in San Antonio).
So guys, should I worry. I know it’s still in normal temp range and hasn’t come even close to overheating. I just got used to it being around 85C! And here in Texas, it will be 90F plus outside in a few months. Should I reconnect EGR? I don't want to, but I don't want to overheat. Any suggestions/ideas appreciated.

Reg in Texas
85 300SD,
Astral Silver, A Beauty!

Well, assuming your EGR was functioning properly before you disabled it, then yes, you should see an increase in temperatures. The EGRs job is to lower combustion temperatures (which limits the production of NOx), and so disabling it should increase combustion temperatures by a bit. I'm surprised that it produced such a noticable change though, when I disabled my EGR (which was indeed functional at the time) I noticed a slight subjective performance improvement, and no appreciable change in temperature as measured by the gauge.

Its possible that the thermostat or some other cooling system part was marginal before, and with slightly increased combustion temperatures is now showing itself as a definate increase in running temperatures. Hopefully some more experienced folks weigh in on the situation.

peace,
sam

__________________
"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)

Yes, disabling the EGR will result in slightly elevated cylinder temperatures. This is quite normal. However, I would be doubtful if you could see the effect on the guage, unless your cooling system has additional "issues". If the system is marginal to start, the extra load from the hotter exhaust might show up in the gauge.

You need to address the typical culprits in these situations:

1) Condition of the radiator. Take it out of the vehicle and thoroughly clean the fins with a proper foaming cleaner, compressed air, and water. You would be amazed how much crap hides in those fins, which look perfectly normal to you when the radiator is in the vehicle.

2) Condition of the inside of the radiator. If its original, and not cared for on a bi-annual basis, the tubes may be restricted, thereby requiring a thorough citic acid flush and/or replacement.

3) Condition of fan clutch. If the fan is not engaging properly at or near 100°C., it won't move enough air to keep the engine temperature down. You see the temperature drop when the vehicle starts moving again. This is typical.

I've listed them in order of the maximum gain for the effort/cost expended. Start on one at a time and see how each benefits the engine.

I can tell you, without any doubt, that thoroughly cleaning the fins (a two hour job outside of the vehicle) will result in a 5°C. reduction in temperatures, at a minimum. If they are really bad, you might get more.

You definitely need to do some work now, before 100°F. arrives.

I don't think that the EGR would have anything to do with how hot your car runs (at least not how hot the coolant gets). Maybe the thermostat isn't working quite right or the temp sensor is going bad.... or you disturbed a wire going to the sensor. That's about all I can think of at the moment, it's most likely that something else was disturbed while you were doing the EGR than the EGR accounting for the temp rise itself.

__________________
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

I need to give my cooling system a good cleaning. What foaming cleanser do you recommend?

__________________
1985 300SD, 203,000 miles, dark blue

Lil Sarah says: "Poor old Grandma Blue Car...She's sad."

Pretty much what everyone said above. Your cooling system was already marginal. After the EGR mod this problem just became more apparent. Just follow through the recommended procedures to place the cooling system back into optimum performance.

As preventive maintenance I am replacing my radiator with a brand new, steel reinforced necked, Behr radiator already in my garage.

There are a few things worth repairing, or completely replacing, before it's completely broke...

Now, that is the proverbial question. I did not have the proper cleaner and I used Dow Bathroom cleaner (OK, you can stop laughing now). It did an acceptable job getting foam down into the fins. Nothing else mechanical can get down there.

What I would really like to find is come "condenser cleaner" that the HVAC techs use in the field for cleaning a/c condensers on houses. Now that would be the ticket.

If you do find something that gets it thoroughly clean, please advise.

When done, take the radiator and hold it up to the sun. You can either see through the fins right to the other side, or you can still see bits and pieces of crap in the fins. I got about 75% out of mine, but, it was not perfect. A proper cleaner would have worked wonders in a much shorter period of time.

I'm not laughing that stuff works pretty good. It is very harsh on painted surfaces so avoid getting it on those.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Those "Coil Cleaners" work great. The problem with them is the shine it leaves behind is accomplished by actually stripping away a layer of metal. A non-acid foaming cleaner would be a better thing to use.
I like that bathroom cleaner idea. I would try a mild soap. Dishwashing detergent maybe. I bet Simple Green would work real good.

Danny

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination

The milder soaps don't dissolve the organic matter which appears to be quite stuck into those fins. Even with the Dow Bathroom cleaner, it takes several applications intermixed with compressed air and liberal amounts of hot water to get a decent job.

Even when "done" you could conceivably apply it again and more crap will come out, although not as much as the original application.

I let the foam sit on the fins for 20 minutes or so until the foam disappeared.

Anyone just take the radiator to the carwash and blast it off? I'm assuming you're removing it when you're doing this cleaning? Of course you have to be careful to spray directly at it and not across it or you can bend some fins or worse. I've done this type of thing many times with window mount air conditioners with no problems, they work much better after doing this. Also the condensor on my truck last year when it was totally clogged with lovebugs...... nasty!

__________________
1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

The question here is whether the pressure washer would be too strong for the fins. In similar manner to the air compressor, the nozzle must be right against the fins in order to achieve any results whatsoever. So, with the nozzle sitting flat on the fins, would the pressure be too great for the fins? If not, it's a terrific solution. But, moving the nozzle away from the fins, even by an inch or so, will result in no water forced in between the fins, where you want it.