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Discussion Starter · #1 · (Edited)
I just replaced my waterpump and thermostat on my car and I have been getting temperature fluctuations between 80C and just under 100C. I have searched on this forum but havent found anything. My guess is that there is air in the cooling system but I dont know how to bleed it. My thermostat does not have a screw on top of it to bleed the air. And I cant find any bleed screw on the block that is described on some posts in this forum. Any ideas as to what I can do?

I have a 1998 c230
 

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'96 C220 n/a diesel
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have u tried running it for 10 min with the expansion bottle cap off? that way the bubbles get out rather than trapped in the system, but do not run it till it get hot or u cud cook ur engine mate
 

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Discussion Starter · #3 ·
i just did that and it helped a little bit - now the temperature fluctuates from 80-90 which is better but is there any way to get it on 80 all the time.
 

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1994 C220 (W202) Classic and 1998 C240 (W202) Elegance
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To bleed the cooling system:

Fill the expansion bottle with a mixture of coolant and water. Keep the cap off.

Turn on your car and let it idle. Squeeze the top radiator hose until no more bubbles appear in the expansion bottle.

It's better to do this when the car is warm and the thermostat is open, thus allowing the water to circulate.

Put the cap back on.

My C220 stays on 80 most of the time and max 85 in traffic.

My C240 stays between 85 and close to 90 and only drops to 80 when I'm on the open road. I suspect the thermostat needs to be changed (155 000km on the clock). But my mechanic said there was no point. I intend to change it at my next service.
 

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1986 190D 2.5 5 Speed
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If you have a bleeder screw (like mine 94 c280) on top of your thermostat housing, crack it until the fans come on or until a steady stream of water comes out (at least 10 minutes). It is a 12mm and on mine, the upper expansion hose connects to it. Squeezing hoses pushes air, but it also sucks air. Michael
 

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Discussion Starter · #6 ·
when i have the heat on the cars temp stays on 80 when i am at a stand still with the engine running, but if i have the ac on then the cars temp starts to rise close to 100. anyone know wwhy this is?
 

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1997 E420 152 k on the clock
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The heater core acts like an additional radiator so makes the car run cooler. If you ever start to overheat in stop and go traffic turn on your heater. The air makes the engine run harder thus the higher temp.
 

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96' C220
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Options...

Given the parameters you outlined, your only option seems to be to burp the hose. It does seem like you have an issue. Your temp should be more stable if all is working properly. The 280 L6 seems to naturally fluctuate the most of the W202's. Our 220 is very stable @ just above 80c in all but extreme conditions.

Good Luck!:thumbsup:

C as in 220
 

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ML320,C230, F250, Bayliner, Mountain Bike, Fleetwood Motorhome etc...
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Did you turn the heater on while trying t get the air out. If not you need to do it... That way the coolant circulates through the whole system...
 

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Discussion Starter · #10 ·
yes i have tried everything and the temp still fluctuates between 80 and 95. should i take my car to the shop?
 

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ML320,C230, F250, Bayliner, Mountain Bike, Fleetwood Motorhome etc...
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yes i have tried everything and the temp still fluctuates between 80 and 95. should i take my car to the shop?
That may just be your thermostat opening and closing. These cars run hotter than you may think...
 

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2001 CLK55 AMG, 2002 C32 AMG
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the aux fans wont actually kick on till 100C or a certain refrigerant pressure which i cant remember. i would say 95 is normal unless it happens when you are actually moving.
 

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1987 190D 1990 300D
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Air pockets cooling system 190D

Last year I was in a remote mountain area and the engine in my 190D started to overheat and before I realized it I blew the heater core...what a mess. We put a bypass hose on the heater and tried everything to get the temp to stay at 80 and it continued to climb. Finally an old mechanic came by and said "I'll bet the thermostat is low in the engine like the old Bronco". He removed the top coolant line from the radiator, filled it till it overflowed with coolant, and reattached it. I don't know if his theory was right, but the temperature locked on 80 and has remained constant for the last year. I don't know if the block arrangements are the same in the 220 but thought this might help.
 

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What do u mena he removed coolant line from radiator?

anybody here have a diy tutorial how to install a thermostat? And how to flush coolant. Im on my phone so searc buttton doesn't work
 

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1987 190D 1990 300D
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We removed the hose going to the top of the radiator and filled it full and quickly reattached it. I could not find a bleeder valve so we gave this a try and it worked perfectly. The engine was pretty warm when we did this, so the thermostat may have been partially open.
 

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'04 G55 '80 280GE '99 S420 '98 E320 2011 E350 2016 GLA250
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Why not do it the EASY way....

Vacuum refilling systems are getting preatty cheap, and takes alot of hassle out of the coolant service..
 

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Discussion Starter · #17 ·
UPDATE:

i replaced my entire cooling system (new rad, waterpump, t-stat). engine still fluctuates between 80 & 95.

I am convinced this is normal. let this be known and the end of it.
 

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1998 Mercedes E200 Avantgarde
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old school

the best advice i got from this thread and This one is get your car warm, further on i tried everything, but my car still had some air in the system. So here is what i did:

1)Take the top radiator hose off
2) fill the system till the water starts coming out of the top ventil of the radiator
3)conect the top radiator hose
4) Warm up your car with the cap off
5) When the car is warm (about 81 C) get in to the car And turn on the heater (red line) on max
6)Cool air will be followed by warm air
7)Call your friend and tell him(her) to look at the level and fill when needed
8) give it some gas, keep the car at 3500 - 4000 rpm for about one minute 9depends on the level
9)turn the car off, put the cap back on
10) Take a small screwdriver and unscrew the bracket by the termostat (top hose in most cases)
11) DO NOT TAKE IT OFF, but put your screw driver just a bit under, when you c that only coolent is coming out without any bubbels YOU are good to GO,
12) tighten the bracket and let the car rest for a bit, then check your level, you might need to add a bit of coolent depending on the amout of air that you got, when slightly lifting the hose.

Make sure you got the correct level, too much and you got too much pressure -> high temperature

HOPE this solves your problems as it did for me

HAp
 

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Hi all: I recently replaced the water pump myself on my 2010 C300 (135K miles) and did it before the water pump failed on me. I also replaced the upper and lower hoses (thermostat was changed two years ago by my mechanic). I'm an amateur FYI'er and had a hell of a time bleeding the cooling system at first, but I think I came up with something that works and wanted to pass it along. Instead of buying those kits (which I did but didn't fit on the reservoir cap) and instead of all those YouTube videos where you wait until 2 cycles of the fan going on, etc., this worked the best: Start with your reservoir cap off (of course) and let the car get up to 80 - which is slightly below operating temperature (which as you all know, is usually between 80 and 100). Then turn the car off, wait about two hours, and you'll most likely see the reservoir go down. Fill the reservoir back up to where it should be and repeat the process. You only need to do this maybe 2-3 times until the coolant in the reservoir goes down - and all the air will come out. My heat worked fine and it's been fine ever since.

I didn't have the heater on at all while doing this, I didn't use the kits, I didn't take a long soda bottle, cut the bottom, and turn it upside down, I didn't let the engine run all the way until the fans came on, and repeated that twice, I didn't rev the engine at all, etc. None of that. All of those methods, in some concocted way, simply didn't work for me. The above worked for me and I think it will work for you. I'm not a mechanic so I don't have a vacuum system, etc. Assuming that we're all MB fans on this forum, you know these cars are wonderful but also tempermental (my 5th German car). Maybe those "classic" methods on YouTube work for Japanese and American cars better. But this worked for me - and was the fastest AND gave me the best degree of peace of mind, that all the air was genuinely bled.
 

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1995 C220
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I will just say, being in collision repair, we have to replace radiators all the time. I have found the vacuum method to be by far the most reliable method to bleed the air out of the cooling system as well as the power steering system. In fact, seems how most of us have had to diagnose our vacuum systems on these cars I would say that you could do it with the hand held mityvac tool fairly easily, just may require lots of pumping. I am glad that method worked for you though. That is similar to how we used to do it before the vacuum systems came about. We would install the radiator, fill with fluid, it would go through the rest of the repair processes(basically sitting for a day or two), then on final inspection we would top off and then go drive the car, and top off one more time. That method worked ok but we had gotten burned a couple times by missing an air pocket that was in the system that wouldnt come out. The vacuum tool I still say is best method. However, based on cost, its really up to the individual if he wants to spend the money on one for piece of mind. I have always taken the attitude that if I think I can do the job, I will always put the money in the tool and do it myself vs paying someone else the same money and possibly doing it wrong.
 
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