1987 300TDT Overheats on long hills - Page 10 - PeachParts Mercedes-Benz Forum

dieseldiehard · #**136** 05-25-2006, 06:06 PM

Hi Steve, I saw your wagon at the gtg on Mother's day, I recall the new A/C hoses (my next chore!).
On the way home from there I thought I shold have asked you to test drive my '87 to see how a normal cooling system operates.

I do not have the sound encapsulation panels on one of my 87's because they were inadvertently thrown out while I was working on it and I can't put blame on anyone because it was in their way for nearly 7 months

but I do not think that factors in at all.

Neither of my 603's run over 100 unless on LONG uphill climbs on a really hot day! I left the AC on while climbing the Grapevine last summer and I believe I saw a tad over 100, maybe 105 but as I haven't made that trip for a year now I am not sure.

Driving at freeway speeds on a 85F day my temp gauges sit around 85 to 90 C unless I come to a stop and let the engine idle right after driving the car hard and in that case 95C or so is normal. And it gradually drops down from there.
Dave may be on to something re: possible cyl head leak, but I would think checking the rad hose when cold would show if it had excessive pressure loss. Or you would be losing coolant.
Are you certain the temp gauge is reading correctly?
Reid

gsxr · #**137** 05-25-2006, 06:22 PM

Oh yeah, I forgot... the sound panels do very little to affect cooling. I have both of mine installed, but I have driven for months with them off, and there was no appreciable difference one way or t'other.

My white car, with a cracked head, would have erratic coolant temps, and the temps would increase rapidly under extended heavy loads. That car also had very noticeable high pressure when cold, which eventually blew out the water pump seals too. It was wrecked before I got a chance to swap the head, though.

sixto · #**138** 05-25-2006, 06:37 PM

I don't remember the earlier posts so maybe this was discussed. Have you tried a different temp sending unit? Maybe try on from one of dieseldiehard or speedy's dozen 603s.

Sixto

dieseldiehard · #**139** 05-25-2006, 06:46 PM

whazzat!? someone's got dozens of 603's, well I'm not jealous, I have pity, plenty of it!
I thought gsxr is the record holder on the '87 300D's
I presently have an oil pressure reading that is wrong, its gotta be the ender which I bought (new) but haven't installed yet. I sure like the mechanical temp gauge on my '71 220, it uses a Bernoulli tube temp gauge.
That and a mechanical oil pressure gauge will never go wrong!

swogee · #**140** 05-26-2006, 03:13 AM

Thanks for the great ideas and suggestions guys.

dieseldiehard, I would have gladly taken up your offer to test drive your 300DT. I must say that your 300DT was a gem! I can only wish that my 300TDT was as nice as yours. (My 1969 Mustang also had mechanical gauges on it that I installed.)

gsxr, it's nice to hear from you. I was hoping you would pick up on this thread.

I have been fighting with this cooling system issue ever since I bought my 300TDT. I would be willing to try a new temp sensor if it would fix the problem, but the gauge is very linear in how it moves. The engine heats up only under heavy load, or high ambient temps. There is no sign of cracked head yet, i.e. no radiator hoses under high pressure when the engine is cold. I have been monitoring this closely. There also appears to be an oil leak around the head bolt next to the intake manifold runner for cylinder 2. I don't think the oil is from the intake manifold, so there may be another reason to pull the head off.

I was thinking if I pull the head off I would have it pressure tested and rebuilt. The head is a "14" casting. Is there a good place to have the head checked out and rebuilt? I'm not sure if I trust a local shop to work on the head. I am assuming there are some special tools needed for a head R and R such as the head bolt socket. How many special tools are there?

Right now I am gathering tools and parts for a front end rebuild so the head R and R will end up being late this year assuming I have a garage by then.

-Steve

gsxr · #**141** 05-26-2006, 12:20 PM

If the electric fan is kicking on at an indicated 105C, then the temp gauge is probably accurate. And with the temps indicating 105C, pop the hood, kill the engine, and observe the fan blade... it should stop almost immediately (indicating that yes, it is engaged). If the fan freewheels to a stop, the clutch is not engaging. Even if it is a new clutch & radiator, this is a simple test that really must be performed before pointing fingers at the cylinder head, or elsewhere.

There aren't many special tools needed to pull the head, just a few, and they're not too expensive... depends if you need to pull the prechambers or not. (I have a set of prechamber tools for sale pretty cheap, if anyone is interested - email me offline.) There's a shop in CA that is allegedly one of the best around, Mark DeGroff is the proprietor, IIRC... they do a lot of Mercedes work. I wouldn't put money into rebuilding a 14 head though... I'd get a 17 and freshen that up, and simply re-sell the 14 on eBay if it is crack free. There's really not much to rebuild, the valves & guides are often perfectly fine, just swap the stem seals and make sure the sealing surface is flat.

sixto · #**142** 05-26-2006, 12:36 PM

Steve, did you check that a CCW clutch fan from an M103 didn't find its way onto your car?

Allergy meds do wonders for my creativity. Which way did that white rabbit go?

Sixto

swogee · #**143** 07-30-2008, 12:03 PM

I thought I'd post an update since it has been a couple years or so.

My 1987 300TDT still overheats on long hills. I recently drove it up Cuesta grade near my house, and with the ambient temp in the low 80's (about 83 degrees F) the engine temp shot up to about 110 degrees C. The A/C was off. The Cuesta grade is about 3 miles long with a 5% uphill grade. The total elevation is roughly 1500 feet.

I recently had my indy mechanic take a look at the overheating issue since the 300TDT was there for another issue, and another pair of fresh eyes looking at the problem wouldn't hurt. He checked it out with a pressure tester, and he found a small leak at one radiator hose which he corrected. However that did not solve the overheating problem. He did note there was oil leaking from the head gasket in the front from around a head bolt and in back of the engine as well. So it looks like the head gasket is getting weak. He couldn't find anything else. He did mention a technical bulletin from MBZ that stated that higher temperatures when climbing grades was normal but I think the engine gets too hot when climbing a grade. I think the engine should only get up to 110 when it is 105 degrees F outside and the A/C is on. Clearly something is still going on.

The engine still doesn't exhibit any signs of the "hard hose" after cooling down that can indicate a cracked head.

I am at a loss as to what is causing the overheating problem. It think it may still be related to the head/head gasket. I think I will have to replace the head and gasket at some point since there are multiple oil leaks.

Also since I last posted, I did take off the auxiliary fan and pressure wash the condenser to remove debris. I also cleaned the fan as well. I used compressed air to blow out the radiator as well.

I don't think the fan clutch is a CCW unit since I bought the fan and clutch together and they were the upgrade fan that is used on the OM606. The fan is a Sachs unit. The only other thing I can think of when t comes to the fan is perhaps the clutch was bad out of the box? I can check the fan clutch again I suppose.

Does anyone have any new thoughts?

babymog · #**144** 07-30-2008, 12:11 PM

Not reading back into your earlier trials (sorry), are you running max. of 50% coolant in distilled / de-mineralized water? Have you tried RedLine Water Wetter or RedLine Diesel Water Wetter?

vstech · #**145** 07-30-2008, 12:30 PM

first off. you live in CALIFORNIA!!! dump that antifreeze mix, do a thorough citric acid cleanup of the block, and get the proper 60 or even 65% WATER to 40/35% G-05/MB antifreeze in there. also lets be SURE you have the right radiator cap. your car should have the 140K mark on it. you need ALL the protection you can get!

swogee · #**146** 07-30-2008, 12:55 PM

Thanks for the additional replies.

I am using a 50/50 mix of R.O. water and Zerex G05 anti-freeze. That is the factory recommended ratio so that is what I am using.

I have considered using the water wetter by Redline, but I'm not sure how much of a difference it makes or if it is just snake oil. I'll have to look into the water wetter and see how much it actually helps.

The cooling system cap has been replaced with a new OE unit. I believe it has a 140 marking on the cap if that means anything.

I have been reading other threads on overheating with the W124 OM603 engine and I have yet to see any definite solutions. The threads never seemed to get resolved. If I do get this problem fixed, I'll post it.

Thanks again.

-Steve

babymog · #**147** 07-30-2008, 02:01 PM

The water wetter is real, "discovered" it when more heavily into racing, also use it on my big diesels, ... there are better ways to trasfer heat than anti-freeze and water. I believe that a bottle costs less than two gallons of fuel.

wbrian63 · #**148** 07-30-2008, 02:07 PM

First - my opinion - unless you've got another TDT to test this against, if the temp climbs to 100 or even 110 and holds - I wouldn't be "too" concerned. Having another car of the same model helps to figure out if this is typical behavior or not.

Remember that 100 is only 212F, 110 is 230f. A properly maintained cooling system with a 15# cap (or thereabouts) will boil water at 239f. Adding antifreeze further increases this number to something just over 260 degrees. (The manual for my '92 300SE says the coolant boils at 266f).

No question that elevated temps beyond the normal 85-90c operating temps create additional stress on the system - affecting the weakest link in the chain (the hoses) first, following on to the radiator, heater core and headgasket. Older cars, like older people, tend to be more fragile.

The issue with overheating is more one of preventing the coolant from boiling. Think about what happens to water in a pan as it approaches the boiling point - bubbles begin to form. What are the bubbles? Water converted to steam. Steam, while a great transporter of heat, does a really poor job of absorbing the heat produced in an engine. When the water boils, the heat transfer effectively stops, and that's what causes damage to the engine - things get really hot really quickly. Oil begins to break down, thermal expansion differentials between dissimlar metals like the engine block and pistons get into the danger zone where you start to have interference between moving parts, etc.

I digress...

The suggestion for the citric acid flush is a good one. Again, the age of the car suggest that there is bound to be some mineral deposits that have formed in the radiator and cooling passages of the engine. Those deposits will reduce the cooling efficiency of the system - get rid of 'em with a citric acid flush.

Water wetter is not snake oil - it's a chemical that is intended to reduce the surface tension of the coolant so that it "grips" the surfaces of the radiator and cooling passages better.

Soap is an effective surface tension reducer, but doesn't work so good in systems involving an impeller like a car's cooling system. As an example of surface tension, on a freshly waxed car, water from the hose will bead into small drops - but soapy water won't. It's an exaggeration of the conditions inside the engine and radiator, but the concept remains the same. You want as good contact between the water and the system surfaces as possible - a water wetter helps with that.

Best bet is to get the system as clean as possible.

Also - again given the age of the car, is it running the original water pump? I've seen many situations where the original pump, although not leaking or squealing, had so much corrosion (in the case of pumps that use cast-iron impellers) and/or mineral deposits that the pumping efficiency was greatly reduced. Poor water flow in a hill-climb situation is a bad thing. I've even seen pumps come out where the impellers were practically gone (stamped steel impellers).

I'm not completely sure about MB - but some cars use a spring inside the return radiator hose (usually the lower hose), to prevent the hose from collapsing under high engine (and consequently high water pump) revolutions. You can test this by getting the car up to temp and opening the throttle to produce the same number of revs as you see climbing the hill and watching the return hose for deformation.

What speed are you climbing the hill at? If the engine is "lugging" (running slowly in a higher gear), that will reduce the coolant flow and allow the heat to build. Downshifting to a lower gear and letting the motor "sing" a bit will help ensure good coolant flow and lower engine load.

A TDT is a big car with a "low power" motor - the turbo is going to cause it to run hotter anyway - don't let it lug on the hill - downshift (obviously don't redline it) and see what happens - assuming of course you can maintain a speed safe for the roadway conditions in the lower gear.

Good luck.

vstech · #**149** 07-30-2008, 02:37 PM

while your manual may recommend 50% coolant mix it is wrong for your climate.
read the bottle of coolant. 50% mix is for -35°F... I doubt your climate ever sees +32°F but if it does get around 0 to -20 then a 60/40 mix is perfect for your car. remember the coolant is NOT there to make the water cool your car better, it's there to keep the water from freezing, and to protect the metal and plastic in your motor from rust/scale.
the BEST coolant is PURE WATER! (well apparently there are some new coolants that use no water, but that's off topic) you want JUST enough antifreeze in the mix to protect your metals and plastics and prevent freezing at the minimum temps for your climate.
140 on the cap is great, that's 22Lbs and will give you maximum protection from boiling.

swogee · #**150** 07-30-2008, 06:09 PM

I wonder exactly how much of a difference the water wetter will make? It sounds like its worth giving it a try.

The reason I am concerned about the higher engine temperature is that the OM603 has a head that is prone to cracking at higher temperatures. My engine has the original "14" head which has a known cracking issue when subject to higher temperatures.

I'm not sure what engine temps other 300TDT's run at up hills. and I have only met one other owner in person and he doesn't live in this area. I have also spoken to a couple 300DT owners about their engine temperatures up the grade and the impression I get is that their engines don't heat up as much. The 1987 300TDT is a rare model so there just aren't many around.

The citric acid flush is good idea, but my cooling system is already pretty clean. The radiator was new when this problem was discovered. The water pump as also been replaced. As I mentioned earlier in this thread pretty much all of the major cooling system components have been replaced (radiator, water pump, thermostat, expansion tank, tank cap, anti-freeze multiple times, fan and clutch.)

I'll have to check on the collapsed hose. That's another good idea worth looking in to.

Thanks for the info on heat transfer and thermodynamics. I am familiar with relationship between pressure and the boiling point of water. I had to suffer through two quarters of thermodynamics in college.

Usually when I go up Cuesta grade it is at the speed of 70 to 75 mph. There is plenty of air flow across the radiator at that speed I believe.

As for running a 60/40 ratio of water to antifreeze, I don't doubt that ratio will remove more heat form the engine. I am only saying that the engine should be able to cool properly on a 50/50 mixture. I will consider the 60/40 ratio as well though.

Thanks again for the replies and the good ideas.

-Steve