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  #1  
Old 10-28-2017, 08:55 PM
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Why is my engine temp rising on grade?

Hello all,

I've finally got my car back together at least enough to drive it, but every time I take it out, 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.

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.

Last edited by crazy4diesel; 10-28-2017 at 09:17 PM.
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  #2  
Old 10-28-2017, 09:01 PM
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Could be thermostat not opening all the way or a clogged radiator. Use an infrared thermometer to check for cold spots in the radiator indicating blocked/clogged tubes.

Good luck!!!
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  #3  
Old 10-28-2017, 09:04 PM
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Oh, I should mention the radiator is brand new, Nissins. Brand new as in 4 years old, but just sat with coolant in it for that time. The thermostat though, I guess is my next thought, it's strange you can hold onto the metal tube that the lower hose attaches too and it's not remotely warm. But you touch the other side of the thermostat housing and it's very hot, or is that normal?
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  #4  
Old 10-28-2017, 09:08 PM
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Still check it for cold spots if you can; but, it is probably fine. Try a thermostat next or check it in boiling water to see if it opens all the way. Could also be corroded away fins on the water pump not moving the coolant.
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  #5  
Old 10-28-2017, 09:21 PM
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Thanks Sugar Bear, I forgot to mention replaced the water pump too, when I had the engine on a stand. I took the car apart 4 years ago, put the engine on a stand, and went through it, replacing gaskets on things like the oil filter, and replacing oil cooler lines, and oil pan gasket, and measuring timing chain stretch, a bunch of stuff. Then I painted the engine bay, and put the engine back in the car while I worked on the rest of the car, I drove it a short bit then but for the most part in the past 4 years, it's been started now and then to go in and out of the garage, on those times I didn't just push it.
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  #6  
Old 10-28-2017, 10:01 PM
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Sounds normal to me. Mine runs 190F normally and will easily top 200 when on the throttle for an extended period pulling a hill.
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  #7  
Old 10-28-2017, 10:27 PM
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Sounds completely normal to me as well. Who would've guessed putting the engine under more load would make it heat up more? Start worrying when it hits 120C for long periods.
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  #8  
Old 10-28-2017, 11:31 PM
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normal probably.
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  #9  
Old 10-28-2017, 11:46 PM
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Not that this is your problem but I had overheating on grades with a Poorly adjusted transmission. I recall the car didn’t gear down early enough on grades. It got bad in hot weather on steep climbs. Oh yeah another time I had a slightly loose upper hose due to a cracked neck on the rad that leaked when I climbed fast. Overheating went away when I fixed that.

There’s always the possibility of slipping plates in the tranny too.

Good luck finding the cause.
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  #10  
Old 10-29-2017, 10:34 AM
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It just doesn't seem normal to me, sure maybe a long hard pass, but a short one? I've owned a lot of diesels, I have a 2012 VW Jetta TDI that never moves off or the middle of the gauge no matter the grade, and I don't slow down.

Even the brown car that was the donor for this car and how I got the manual transmission, it never moved off of the 80 degree mark, no matter how much you pushed it. Of course it was an NA diesel too though.
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  #11  
Old 10-29-2017, 11:47 AM
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I was going to suggest that the problem might be the fan clutch, but read that it was replaced. What brand did you use? It is hard to believe, but most of them are made in China, even from German name brands. My radiator/A/C shop guys have tried them all, and none are as good as those gotten from Autozone (believe it or not). They are actually US made (USMW= US Motor Works), and are more aggressive than any other brand. I always use this test on fan clutches: With the car warmed up, wrap your fingers with a rag and try to stop the fan while the engine is idling. If you can stop and hold the fan (on a real bad one you can actually fling it the opposite way!), the clutch is bad. Yes, you can even get a bad new one out of the box.
You may also know this, but for other's benefit: these cooling systems need to be filled up from the top radiator hose, as well as in the expansion tank. I usually get a little less than a gallon in the expansion tank, and at least another gallon through the top hose (in a completely empty system).
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  #12  
Old 10-29-2017, 11:51 AM
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Quote:
Originally Posted by crazy4diesel View Post
Hello all,

I've finally got my car back together at least enough to drive it, but every time I take it out, 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.
What was the ambient temp when you observed this? Climbing short hills should not cause the temp gauge to reach the unlabeled mark which is 100C , 212F and require you to turn on the heat to lower it, the thermostat should do that automatically. I have no experience with Evan's waterless coolant. Maybe your problems is related to its use?

Other things to check:
Check thermostat, try another one.

Is temp gauge accurate?

water pump belt tight?

coolant expansion tank cap functional?
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  #13  
Old 10-29-2017, 11:58 AM
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Quote:
Originally Posted by crazy4diesel View Post
It just doesn't seem normal to me, sure maybe a long hard pass, but a short one? I've owned a lot of diesels, I have a 2012 VW Jetta TDI that never moves off or the middle of the gauge no matter the grade, and I don't slow down.

Even the brown car that was the donor for this car and how I got the manual transmission, it never moved off of the 80 degree mark, no matter how much you pushed it. Of course it was an NA diesel too though.
Modern cars dumb down the gauges to sit in the middle and not move unless there's a problem so people don't freak out about the engine temperature rising when more power is requested from it.

The thermostat opens in stages, it's perfectly normal for the engine to run under the 100 mark when you're pulling up hills or something. As long as it comes back down when you're on flat ground or idling, you're fine.

The one thing you should check, though, is your boost pressure. If the turbo is boosting more than about a bar you won't make any more power, you'll just make a lot more heat.
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  #14  
Old 10-29-2017, 12:04 PM
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I'll check the fan clutch, it's very tight when cold, but haven't checked when hot.

I used the better thermostat at the time, Whalen or something like that, I have a new Mehle one in the box, I'll try it out. I saw on some site, they drilled holes in the thermostat?

I'm not sure the temp gauge is accurate, nor how I'd check it?

Pump belt is tight, about 1/4" deflection when pressed on the middle.

Tank cap seems fine, of course with the waterless coolant it doesn't pressurize as much, only to about 4-6 pounds.
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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.
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  #15  
Old 10-29-2017, 12:06 PM
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Not sure how to check boost pressure, it does feel strong, but not out of line from what I'd expect.

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