1987 300TDT Overheats on long hills - Page 11 - PeachParts Mercedes-Benz Forum

Brian Carlton · #**151** 07-30-2008, 08:15 PM

Quote:

Originally Posted by swogee

I used compressed air to blow out the radiator as well.

Have you ever had the radiator out of the vehicle to thoroughly clean the passages between the fins?

This job cannot be done in the vehicle.

Additionally, you'll need a pressure washer or some industrial condenser cleaner.........or both.

The radiator may look clean to you..........but, it's not. The fins are packed with fine debris that you cannot see.

When you remove the radiator..........hold it up to the sun and look through the fins..........you'll see the problem in two seconds.

Hatterasguy · #**152** 07-30-2008, 08:28 PM

I thought the OP replaced the radiator?

If not bet you a 6 pack thats his problem.

Brian Carlton · #**153** 07-30-2008, 08:33 PM

Quote:

Originally Posted by Hatterasguy

I thought the OP replaced the radiator?

If not bet you a 6 pack thats his problem.

I didn't reread it all back to the beginning..........but, why is he blowing a new radiator out with compressed air............??

Hatterasguy · #**154** 07-30-2008, 08:34 PM

I skimmed the first post, and he said new radiator.

It really sounds like an old radiator that isn't as good as it used to be. I bet I could blast up that same grade with my SDL and it would never get over 100C.

vstech · #**155** 07-30-2008, 08:38 PM

the things we keep recommending to him, he doesn't wanna do...

your cooling system may have all new parts, but if your BLOCK has not been cleaned, it has 21 years of scale, rust, sediment etc in it. truly, a citric acid flush will put your block back to new condition so the heat produced in it can be removed in a timely fashion.
it is a good idea to verify the temp sender is accurate.
it's also possible that a properly working motor should be able to dissipate the heat with a 50/50 mix... however YOUR motor is not working properly. you have changed all cooling system components. and it only overheats on very long steep grades. give the car more chance to remove more heat. go for the better mix. RO water is NOT as good as DISTILLED water! a 50/50 mix is NOT as good as a 35/65 mix. a block with 21 years of scale and sediment in it is NOT going to cool as well as a freshly acid cleaned one.

Brian Carlton · #**156** 07-30-2008, 08:45 PM

Quote:

Originally Posted by Hatterasguy

I skimmed the first post, and he said new radiator.

.

Yep, thanks..........I missed it.

Time to take John's advise and do a citric acid flush on the block. Nothing left as a possibility.............

slept thru it · #**157** 07-31-2008, 12:35 AM

I'm far from an expert. But I just read a 1994 MB service bulletin which described this performance as normal under high load, stating that the temp. in some cases can nearly reach the red. (July 22, 1994, message 322)

swogee · #**158** 07-31-2008, 04:21 AM

Thanks again for the replies everyone.

The radiator was new when I replaced it roughly four years ago. The vehicle has only had about 10K miles put on it in the last 4 years or so, which is not enough time to clog the fins up again. I did use compressed air to blow the radiator back out just in case when I was cleaning the condenser out. I was attempting to push dirt from the condenser mainly. When I took the aux fan out, I did use a pressure washer to remove any built up dirt from the condenser. Additionally, I did inspect the fins for debris and there wasn't enough to block the airflow prior to cleaning, and there was virtually none after the pressure washing.

I did indeed also get a copy of the bulletin from my indy mechanic stating that the temperature rise up hills and under loads can come close to the 120 degree C mark so I am familiar with that as well.

One other thing mentioned is that R.O. water is not as good as the D.I. water. I will admit that R.O. water has an 85 to 95 percent reduction in ions vs. 100 percent reduction of ions for D.I. water. In this case I used R.O. since the vast majority of ions/minerals are removed from the water and I felt that to be adequate for the cooling system. It would be different if I was filling a battery though, which has no tolerance for any extra ions. I do have access now to a unlimited supply of D.I water now so I can use it instead.

I get the impression that the consensus is that a citric flush would be helpful improve the cooling ability of the engine. I'm not sure exactly how much it would help, but at this point it can't hurt I suppose. I'll look into it.

I'll also verify the temp gauge is reading correctly just for completeness.

vstech, I'm sorry if it seems as though "I'm not doing the things that people are recommending", but I want to make sure that there is good reason for doing something before I go and do it. I'm not an expert by any means. I'm just here to learn and comprehend. I do appreciate your suggestions and your posts.

Thanks again for the ideas and suggestions.

-Steve

Bio300TDTdriver · #**159** 07-31-2008, 10:50 AM

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Brian Carlton · #**160** 07-31-2008, 11:28 AM

Quote:

Originally Posted by Bio300TDTdriver

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On blue bar above first post, you'll find the button "thread tools".

Press it and then press "subscribe to this thread".

Hatterasguy · #**161** 07-31-2008, 11:55 AM

Was the water pump replaced? GSXR has pictures of them with the vanes half gone.

I'd do a good flush and replace the water pump if its original.

gsxr · #**162** 07-31-2008, 12:08 PM

Steve & co., at the risk of repeating what I've already said in the previous 9 pages...

1) 120°C is not acceptable outside of Death Valley in August. The factory bulletin specific to the OM602/603 says 110°C, click here to read.

2) The citric acid flush can help if there is serious corrosion or scale problems. But IT IS NOT a magic cure-all for overheating problems. It is also a royal PITA to do properly (emphasis on "properly"). It requires a forced-open t-stat (special tool), running the engine to operating temp, letting it cool down, draining, flushing, re-filling, and repeating twice more to ensure all the acid is removed (don't forget the heater core). Unless you have hot water to flush with, it can take hours to allow the engine to cool enough to safely flush with cool water (garden hose, etc)... EACH of the three times. Click here to read the factory procedure.

3) Here is brief review of my overheating problems from 1997/98, when I bought my blue 1987 300D: It was fine in winter (85-95°C), but ran at 105-115°C in summertime, city or freeway. The radiator had been replaced in 1993 (new OE/dealer radiator) so I assumed a 4-year old radiator couldn't be the problem. The fan clutch was bad, a new one did help, but only reduced temps to 105-110°C. New (OE/dealer) water pump and thermostat didn't help. Cleaning condenser & radiator fins (removed from car) didn't help. 20/80 mix of distilled water, plus Water Wetter, didn't help. In desparation I tried a new (OE/dealer) radiator, depsite the "old" one having only 4-5 years and ~50kmi on it. Presto, instant temp reduction to 90-95° at all times. For the next few years I couldn't make the engine exceed 100° under any circumstances, including WOT up grades in 90°F ambients.

4) My car has been slowly increasing in engine temp over the past 3-5 years or so. Not bad, but enough to notice. It's only under high load though, even on level ground, and in cooler temps. It shouldn't go to 100-105° but it can. I installed a new OE/dealer t-stat 4 months ago and this did seem to help a little (despite both old & new appearing to operate the same in a pot of boiling water). I recently had the opportunity to ascend a 6% grade for about 5 miles, at 70mph, 90-95°F ambients (it cooled from high 90's at the base to low 90's at the top), EGT's hanging around 1200°F. Engine temps started at the usual 95°C but slowly increased to 110°C by the top of the grade. Not enough to seriously concern me, but it wasn't doing that when the radiator was new. I did a citric acid flush a few years ago but it made no difference.

5) My sister's 1987 300D has a serious cooling problem as well but so far, we have not been able to pinpoint the cause. Around town it will shoot up to 110-120°C with the AC on, and on the freeway it only drops to about 100°C (this is in 95-105°F ambients, in central CA). It had a new OE/dealer water pump installed in 2001, along with a new fan & clutch. A new radiator (2005?) and thermostat (this year) did not help. We did discover that the fan clutch often was not engaged, meaning there was not enough heat coming off the radiator to trigger it (it should be engaged by 100°C on the dash gauge). We tried two different, known-good clutches with the same result. The car is 500 miles away from me so I can't easily work on it to figure out a cure. But we don't know why there's not enough heat getting from the engine to the radiator. The engine is smoking hot but the radiator is not, the apparent temps entering are more like 80°C instead of >100°C. Very strange.

6) FYI, to test your fan clutch, you need the engine temp at 100°C or above. Stop the car, pop the hood, kill the engine with the stop lever on the side of the IP. The fan should stop spinning within 1-2 turns. Compare this to when the car is cool or warm (60-85°C), you'll see when it's not engaged it will slowly spin to a stop (probably 10 turns, not 1-2). If it's not engaged, it does NOT necessarily mean the clutch is bad... a new clutch won't engage either, if it is not getting a blast of hot air directy on the bimetal spring on the face.

7) A cracked head, or failing head gasket, can cause engine temps to be higher than normal, and/or allow engine temps to rise very rapidly under full load (i.e., a full throttle blast from 0-80mph would cause temps to skyrocket from say 85 to 100°C in 15-20 seconds, when they normally would not). If there is zero coolant loss, and absolutely no sign of the "high cold pressure" syndrome, the head/gasket problem is unlikely (but not impossible).

8) I've personally seen the 124.133 operate under heavy load at high ambient temps, without exceeding 100-102°C. So I know it's possible, and I also know that engine temps of 105-115° under lighter loads (and/or lower ambient temps) is not normal. But to date, I have not found a smoking gun with the miracle cure.

swogee · #**163** 07-31-2008, 12:09 PM

I did indeed replace the water pump. I think that was item #2 after the radiator. Thanks for the suggestion though.

Unfortunately, this thread is getting so long that it is difficult to get a handle on all the things that have been done/mentioned without spending an hour reading it all. Oh well, I suppose that was bound to happen.

Keep up the good ideas.

My research on the citric acid flush indicates that it is a total PITA that will take the whole day. Time to start looking for 2.2 lbs of citric acid. If it works that would be great!

-Steve

gsxr · #**164** 07-31-2008, 12:40 PM

Quote:

Originally Posted by swogee

My research on the citric acid flush indicates that it is a total PITA that will take the whole day. Time to start looking for 2.2 lbs of citric acid. If it works that would be great!

Steve, it would be great if you would do the full acid flush procedure, then re-fill with 20-30% MB/G-05 antifreeze, a bottle of Water Wetter, and top off with distilled water. If that makes no difference, it does eliminate the acid flush as the magic cure. If it DOES drop your temps drastically... looks like I'll be grabbing the salt shaker to season my hat, when I have to eat it, lol...

swogee · #**165** 07-31-2008, 01:07 PM

gsxr, I was wondering when you would chime in. I would have to agree with your comment regarding the citric acid flush. I am not entirely convinced that the acid flush is magic cure that it is purported to be, but it can't hurt to try it since at this point since I have tried most everything else. I'll try the water wetter since I have been reading good things about that as well.

I am also trying to arrange a comparison drive with another 1987 300TDT in my area. Apparently there is one other 300TDT in my area, and my mechanic mentioned there might be a possibility of a comparison drive. The other 1987 300TDT apparently has a new "22" head on it since the head was just replaced recently. It would be interesting to see what the other 300TDT heats up to on Cuesta grade. I'm pretty certain that it won't get past 100 degrees C, but I'll wait and see.

-Steve