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  #16  
Old 10-29-2017, 12:12 PM
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Do not drill holes in the thermostat! One of the modes it operates in is bypass, drilling holes will defeat bypass!

You can check the temp gauge with a infrared thermometer by aiming it at the temp sender on the block. Also aim it at the upper rad hose and the lower rad hose and report all numbers.

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  #17  
Old 10-29-2017, 12:25 PM
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If you're getting a very quick rise with a very short hill climb, I'd be looking for an air pocket trapped in the system somewhere. Even if the thermostat were stuck closed, it shouldn't raise the temperature that fast. That said, 100˚C isn't out of line if you have the A/C on and it's a hot day.

Another possibility is a head gasket breach or small crack in the head allowing high pressure gas to create a localized hot spot. When climbing a hill or hard acceleration, you are at max boost and max pressure in the cylinders - favorable conditions for a breach to leak to the coolant passages. Given you haven't even reached 100˚C yet, I wouldn't worry too much about head gaskets at this time.
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  #18  
Old 10-29-2017, 12:29 PM
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Quote:
Originally Posted by crazy4diesel View Post
Hello all,

The temp rises more than I would like even on local short grades. At idle is sits just above the 80 mark, and then there is another unnumbered mark which I am going to assume is 100. When ever I hit the slightest hill for much distance, the needle starts headed toward that 100 mark, it hasn't actually reached it yet, because I back off the throttle, and turn on the heater, which helps for a second, but then once the heater core water is up to temp, and circulating with the rest of the water, the temp starts rising again.

Here's what I've done:

Replaced the thermostat, water pump, all hoses, and tested the heater core (way back when I had the engine on a stand).
Replaced the fan clutch (just today)

The water in the upper hose is HOT, and the water in the lower hose remains quite cool, surprisingly cool in fact.

What should I try next?

I should mention I removed the auxiliary water pump from the heater hose line, and I am running Evan's waterless coolant.
Idling above 80C, an immediate temp rise when even moderate power is called for, and a cold lower hose, all point to lack of circulation through the radiator. The only circulation is through the bypass circuit, which does not provide any heat rejection other than the heater core.
Suggest inspection of the thermostat, and/or exchange with another one as a first step. Stealth rags have been known to sneak into hoses in the dead of night.
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  #19  
Old 10-29-2017, 04:11 PM
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It's always been the case that these engines run hot on long steep grades. But a normal hill shouldn't make it hit 100. Many owners are too forgiving of the car running hot, 120 is far beyond acceptable under any circumstance. Also, don't test the fan with your fingers if you want to keep your fingers.

If you feel the car is running hotter than it should, and the fan and thermostat are ok, try a compression test. Low compression will certainly make it run hotter. Also make sure that your oil cooler thermostat is working (if so equipped). Don't be drilling your thermostat: if it doesn't work, replace it.

You can check boost pressure by disconnecting the Alda line and temporarily installing a boost gauge. (You want to check the Alda line anyway: if the Alda is blocked, turbo boost is just a drag on the engine.)

I use plastic thermometers at various points in the engine compartment. These give me a quick way to check temperatures accurately. Infrared thermometers only give you an approximate reading:

CoolCat Express Corp.: Testing Products for the Cooling System
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  #20  
Old 10-29-2017, 06:48 PM
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Similar with my 1985 300D. I also eliminated the aux heater pump and use Evans, in my 1984 also. The 1985 overheats at 5 min stoplights on >90 F days, creeping up to 120 F. If I rev to 1200 rpm in neutral, it quickly drops. Seems the coolant doesn't flow thru the top hose in neutral (700 rpm) since I saw that testing w/ water. I have tried many things, including running on pure water for a week and more citric flushes. I tried several T-stats, a radiator, and new water pump. The lower hose is cool while the bypass is hot, suggesting the bypass doesn't fully close, but I tested the housing in hot water and T-stat appeared to close tight by 80 C. I doubt due to Evans since this started after at least a year running it, and same deal going back to water. The 1984 doesn't act like this. I thought of just blocking the bypass, but it is good in keeping the block uniform while heating up. It is "merely interesting" and hasn't kept me driving like this for a few years, plus don't know what else to try. The only correlation I imagined is this started after adding 1 tube of Aluma-Seal, but I doubt that forms hard gunk. Perhaps I had just lowered the idle speed. On the plus side, I seem to get better mileage, and no worries w/ Evans boiling over.

My son watched the T-stat in I think the 1984 car in climbing the Grapevine on a 95 F day (~3000 ft in 10 miles). He saw 104 C, then quickly dropped after the peak. This was a test after changing to Evans. He drives fast, so was probably doing 65 mph going up. I have seen that an air/vapor bubble can make the gage read high, while the block is normal. This was over many years, so my facts may not be perfect and I can't offer more "this or that" details.

BTW, for spare coolant I carry Sierra ($15 Ace) since pure propylene glycol (original Evans, now a mixture w/ ethylene glycol). It specs 5% water, but since I run w/ the reservoir cap loose any might evaporate. Good luck.
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  #21  
Old 10-29-2017, 07:37 PM
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It looks like I'll be dropping that new thermostat in it, and reporting back. I'll keep you all posted.
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  #22  
Old 10-29-2017, 07:38 PM
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Can I buy this U.S. made fan clutch for the OM603.

WILL AutoZone really have it for me?
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  #23  
Old 10-29-2017, 08:41 PM
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Quote:
Originally Posted by Father Of Giants View Post
Can I buy this U.S. made fan clutch for the OM603.

WILL AutoZone really have it for me?
I think all Duralast fan clutches are made by USMW. It will be on the high end price wise, but I think well worth it. Brands like Hayden and the like are junk out of the box compared to the USMW. Again, my friend at the radiator shop has done as many as a dozen fan clutches in a week during the summer months, and he has tried them all over the years. I trust his experience (many years worth)......Rich
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  #24  
Old 10-29-2017, 08:52 PM
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Originally Posted by Mxfrank View Post
Also, don't test the fan with your fingers if you want to keep your fingers.
Although I would not use my fingers (even wrapped with a rag) for testing a NEW fan clutch, I have done it on many suspected bad ones without issues. My friend at the radiator shop does it all the time, and he still has all his fingers. I have also heard of using a rolled up magazine, and of course that works well also. This video shows what I am talking about, and the guy does not even use a rag around his fingers.
https://www.youtube.com/watch?v=cOXcrbQRDWU
Point being, if you can stop the fan (using your tool of choice) while the engine is warm and idling, the clutch is bad.
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  #25  
Old 10-31-2017, 12:43 PM
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I forgot to mention that I also tried several fan-clutches, both from junkyard and a new one, but I still suspect the fan-clutch since (as Rollguy says) even new ones are questionable. Ed China on Wheeler Dealers showed the "grab fan w/ gloved hand" test, but I value my fingers. My fan doesn't seem to move a lot of air at idle, but blows well when the engine is rev'ed (engine hot). Perhaps not the whooshing sound that others describe, but seems the same air-flow as my 1984 which doesn't creep up at idle. Also, even w/ the electric fan turns on, the gage doesn't drop, though I feel much air moving. I still suspect the coolant isn't flowing into the radiator at idle, but can't figure why since I changed water pumps and T-stat.
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  #26  
Old 10-31-2017, 05:30 PM
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Quote:
Originally Posted by crazy4diesel View Post

The water in the upper hose is HOT, and the water in the lower hose remains quite cool, surprisingly cool in fact.
Pull the radiator and have it rodded out, it is clogged. When driving up a hill, there is more heat to reject from coolant, the clogged rad is just too "small".

The upper and lower should feel about the same temp when the engine is fully warmed up, ( like after a drive ) . This test is also valid for a heater core however a clogged one won't cause your problem.

Also, the fan clutch isn't the problem because the lower hose is very cold. If the fan wasn't working the lower hose would be nearly as hot as the top.
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  #27  
Old 10-31-2017, 06:18 PM
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Quote:
Originally Posted by 97 SL320 View Post
Pull the radiator and have it rodded out, it is clogged. When driving up a hill, there is more heat to reject from coolant, the clogged rad is just too "small".

The upper and lower should feel about the same temp when the engine is fully warmed up, ( like after a drive ) . This test is also valid for a heater core however a clogged one won't cause your problem.

Also, the fan clutch isn't the problem because the lower hose is very cold. If the fan wasn't working the lower hose would be nearly as hot as the top.
First of all, these radiators cannot be rodded out. Second, it is a new radiator (third post).
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  #28  
Old 10-31-2017, 06:53 PM
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Quote:
Originally Posted by 97 SL320 View Post
........

The upper and lower should feel about the same temp when the engine is fully warmed up, ( like after a drive ) . This test is also valid for a heater core however a clogged one won't cause your problem.

.....
Not true. The upper part of the radiator is the hottest. It gets progressively cooler the lower you go on the radiator. I have done actual feel test by hand and verified it.

edit: I didn't provide why

The radiator is a sepentine of horizontal flat tubes with fins attached to the tubes to aid in heat removal. The hot coolant from the head enters the top of the radiator, zig-zags through the spentine tubes and exits the bottom of the radiator. As the coolant zig zags from top to bottom of the radiator, it gets cooler due to air flow/ heat removal by the fins.
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Last edited by funola; 11-01-2017 at 11:52 AM.
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  #29  
Old 11-01-2017, 06:01 PM
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Quote:
Originally Posted by funola View Post
Not true. The upper part of the radiator is the hottest. It gets progressively cooler the lower you go on the radiator. I have done actual feel test by hand and verified it.
Only at idle and lower ambient temps where rad capacity if far greater than engine heat output.

My example stated
Quote:
The upper and lower should feel about the same temp when the engine is fully warmed up, ( like after a drive ) .
If we overcool water entering the engine, you will get thermal shock.

When the lower hose is cold, the thermostat is either closed due to a cold engine or the radiator has a flow problem due to a clog or water pump impeller issue.
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  #30  
Old 11-01-2017, 07:46 PM
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Why is my engine temp rising on grade?

Another thing that you may want to look at is your coolant mix; If you have too much coolant In the mix, the radiator fails to radiate that heat and the fan cultch engagement could be delayed.

I have seen notes where Mercedes Benz use to pay close attention to this come service time.


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