by "BJohnson11" (brettjohnson01)
Published 05/02/2017 at 22:50
by "BJohnson11" (brettjohnson01)
Published 05/02/2017 at 22:50
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So still had some hot running issues today. Drove the 300D into work, and on both the way in and the way out, temp climbed fairly quickly to just under 100C but then halted there. No movement in either direction really more than a degree or so. Seems baffling. When I tried burping the system as I had done previously, the temps didnt really drop at all, unless I turn the heater on in which case they drop pretty quickly.
So my initial thought was a lack of coolant flow through the block and radiator. But the only thing that could cause that would be a seized or otherwise broken water pump right? And I had the water pump replaced around 5k miles ago, so I’m not inclined to think thats the issue. The other thing is, if the water pump wasn’t pumping, why would temp hold so steady at 100C? The only reason I have to believe the water pump may have failed is that when I did the full coolant drain and flush, when I filled the coolant back up, the block probably wasn’t filled before the car was started so the pump would have been running dry, but that shouldn’t really matter at all right? The pump design is just a shaft with an impeller on the end of it. Is there anyway to test that the pump is circulating fluid other than say, taking the upper rad hose off and running the car?
The next bit of confusion is that I can drive the car 30+ miles with it around 100C the whole time, but when I park I can pop the coolant overflow tank cap off with no drama. That tank isn’t really part of the coolant circuit (Coolant tank has a big hose to lower rad, but then the hoses go T-stat housing outlet to lower rad, upper rad to T-stat inlet), so hot coolant wouldn’t be flowing through there on it’s own right? Because it’s not part of the circuit?
So where I’m at now is a state of utter confusion. I have another water pump on order and if I dont have answers by the weekend (I have another car I can take into work for a day and then I’m having LASIK done thursday so no car needs till Monday), I’ll throw it in, but I really dont feel like doing all that work to replace a component that was recently replaced.
Oppo, any help? Any advice? I’d love to be missing something obvious.
"Biased Plies" (biased-plies)
05/02/2017 at 22:59, STARS: 0
It varies car to car but 100C doesn’t strike me as out of the ordinary for a normal operating temperature. What temperature is the centre of the water temp guage marked at?
Just as a suggestion, if you’re worried, maybe put in a lower temp thermostat so it opens earlier and allows coolant through the rad sooner.
"Urambo Tauro" (urambotauro)
05/02/2017 at 23:01, STARS: 1
What happened when you tried burping the system? Did any air work its way out? I don’t want to put you on a wild goose chase, but it’s important to get the whole air pocket thing out of the way first.
I noticed in a previous post that you said that the t-stat is mounted rather low. Is there any chance that your application is one of those that requires a vacuum bleed for a complete fill?
"HammerheadFistpunch" (hammerheadfistpunch)
05/02/2017 at 23:01, STARS: 1
I went to ask the guy today but he wasn’t there. I’ll check back tomorrow
"BJohnson11" (brettjohnson01)
05/02/2017 at 23:01, STARS: 0
So when I first bought it, it would run around 85C. I agree 100C isn’t out of the ordinary, but I just don’t know what would cause the change. Middle of the gauge is 90C.
Re the thermostat, it’s an 80C thermostat, but that’s the opening temp, not sure what the full open temp is. But I replaced the thermostat when I just did the flush this weekend.
"BJohnson11" (brettjohnson01)
05/02/2017 at 23:14, STARS: 0
No air that I could tell. Part of me says it’s gotta still be air, but the coolant overflow is the high point so I had it idling with that open for a few minutes on a couple separate occasions and didn’t notice any air. Don’t think the t stat has a bleed valve.
"Biased Plies" (biased-plies)
05/02/2017 at 23:18, STARS: 0
My first inclination would still be swapping the thermostat. Was is changed when you had the water pump changed 5k miles ago? Does the timing of these symptoms coincide with the car seeing the highest ambient temps it has done since changing water pump? (Or was it change during or before last summer?).
I’m just thinking it may have been changed for a higher temp one when the water pump was done if the water temp stays so consistent.
"BJohnson11" (brettjohnson01)
05/02/2017 at 23:22, STARS: 0
The history of the t stat and pump was, pump started leaking in maybe, November? Had both replaced by a shop then, but afterwards, temp ran higher than it did previously (85ish C vs 95-100C). So I guess the t stat that was in the car when I bought it could have been a lower temp one...
But lot of researching online pegs standard operating temp around that 90C zone. Ambient temps if anything have been lower when it’d been running warmer, though it’s been heating up as of late.
"Biased Plies" (biased-plies)
05/02/2017 at 23:26, STARS: 0
That would settle it for me. I think I’d leave the pump and swap the thermostat for an OEM one and see.
"RallyWrench" (rndlitebmw)
05/02/2017 at 23:27, STARS: 0
You can tell if the pump is working by squeezing the upper radiator hose while revving the engine, you’ll feel it expand. Not likely the issue. It’s possible for corrosion to block passages and restrict flow if the coolant mixture hasn’t been maintained to prevent it.
It could be an air block, but I’d expect pressure in the reservoir and boilover if that was the case, and if the heater works properly it’s a pretty good indicator that it’s bled. Have you lost any coolant? Do you have an infrared gun? It’s possible the new thermostat isn’t in fact opening at 80, or the temp sender is lying.
"BJohnson11" (brettjohnson01)
05/02/2017 at 23:29, STARS: 0
But I did just replace the thermostat with an “OE exact” one, so same temp and whatnot. Maybe the previous owner just had a lower temp one (I think I read 75C instead of 80 is available).
"BJohnson11" (brettjohnson01)
05/02/2017 at 23:34, STARS: 0
Hmm I’ll check the upper rad hose thing tomorrow. Shouldn’t be significant blockage, when I did the coolant flush I ran a couple gallons of water through the block and then radiator and they came out pretty clean. Haven’t lost any coolant (oil clean as well). No IR gun but I’m sure I can get my hands on one.
As another comment suggested, it could be possible that both the thermostat I put in and the one the shop put in previously were, even though the OEM temp, is a higher temp thermostat than what was in there when I bought it.
"Biased Plies" (biased-plies)
05/02/2017 at 23:38, STARS: 1
I think Mercedes still makes and sells parts for many if not most of their older vehicles so I’d likely have gone with that but you can try a lower temp one to be sure. You live in a warmer climate, iirc (CA, right?), so it’s not gonna hurt.
"BJohnson11" (brettjohnson01)
05/02/2017 at 23:44, STARS: 1
Very fair, and worth a shot. Thanks for the insight!
"415s30 W123TSXWaggoIIIIIIo ( •_•))°)" (415s30)
05/03/2017 at 00:09, STARS: 0
It was super hot today and I drove the 300D, they will go to about 100 and be ok, but the diesels can get a bit weird at the limits. All the Merc diesels I have had act very differently depending on temp and humidity outside. You just have to get to know them, they are not a normal vehicle! Mine is a totally different car after it’s warmed up and has driven a few miles on the highway. Be ready to replace air cleaner mounts, they break on US models, but I highly recommend getting the tougher set up from mercedessource.com. Also if you have an EGR, get the delete plate and get that shit off the car, don’t hesitate.
http://www.dieselish.com/egr-delete-kit/
"415s30 W123TSXWaggoIIIIIIo ( •_•))°)" (415s30)
05/03/2017 at 00:12, STARS: 1
Yeah 90 is better, I only get to 100 on a hot day with the AC on for my dog. My Merc mechanic says its ok but when the other fan comes on I know it’s feeling the heat.
"BiTurbo228 - Dr Frankenstein of Spitfires" (biturbo228)
05/03/2017 at 04:39, STARS: 0
Have you considered that it might actually run at ~100C by design?
I know the MG F runs at a little over actually, and keeps pressure in the system to stop the fluid boiling.
The other thing is the design of the gauge. My dad’s car has a fault somewhere in the gauge electrics that causes it to over-read for a given temperature. I’ll quiz him on what it is specifically as electrics aren’t really my thing, but it may well be the gauge that’s the problem not the cooling system.
"brianbrannon" (brianbrannon)
05/03/2017 at 11:47, STARS: 1
If the pump was bad it would actually overheat. Why assume that the gauge is that accurate? You had low and dirty coolant before it’s possible the gauge is only reading correctly now. But if you want lower temps then feel along the fins of the radiator to find the cool spots and the replace it to fix the clogging.
"BJohnson11" (brettjohnson01)
05/03/2017 at 12:07, STARS: 0
That was why I was thinking it wouldn’t be the pump. Bad pump would be just straight to overheating. I’ll look back through the receipts from when I got the car a year ago, but I believe the PO said he had the radiator replaced.
Thinking it may be a worn out fan clutch? Wouldn’t make sense that the radiator isn’t getting enough air when its at freeway speeds, but I’m sure the fan clutch hasn’t been replaced in years and a weak fan could certainly cause issues.