Changed antifreeze.... - PeachParts Mercedes-Benz Forum

subman60 · #1 09-07-2016, 11:29 AM

Changed the antifreeze and t-stat on my 240d. Before the change car temp gauge needle was sitting on the line just above 80c when driving in town. On the interstate it would go to just below the 120c line. With the AC on it would go even higher. I drained the old antifreeze from the radiator and block. Took the garden hose and flushed both the radiator and block until water coming out was clear. I put in a new 80c t-stat and filled it with 1 gallon of Zerex GO5 coolant and 1 gallon of distilled water, that's all it would take. Nothing has changed temp gauge still reads the same this morning as before. I've never used a flush kit before when changing antifreeze but could that be what I need to try with this auto? I did this change with the car on ramps that I believe is why it only took a total of 2 gallon to fill. Any ideas why it is running so hot?

BWhitmore · #2 09-07-2016, 11:47 AM

Changing the thermostat will have absolutely nothing to do with your overheating engine unless the thermostat was stuck closed (which you would know within 10 minutes of initially starting the engine in the morning). The purpose of the t stat is to allow the engine to warm up soon thereby allowing the engine to run better when at operating temperature. Your overheating problem is probably related to a defective water pump, clogged radiator, defective radiator cap, major coolant leak, defective fan, slipping belts, bad head gasket, cracked head/block, or a combination of above. Also a good idea to check the accuracy of your temp gauge.

Rogviler · #3 09-07-2016, 11:49 AM

Have you also made sure that the outside of the radiator is clean? I had an overheating problem just like that (and even with a broken thermostat, I later found out), which turned out to be the space between the radiator and condenser being half-filled with leaves and dirt.

If that checks out then I might suspect other things, but start cheap and easy first.

-Rog

leathermang · #4 09-07-2016, 12:02 PM

As has been pointed out... you changed the antifreeze when it was not the cause of your overheating... nothing wrong with that... but now on to finding the actual problem... suggest only fixing one thing at a time so you will know what was going wrong in the first place...although on cars this old... it may be multiple things and the improvement be in stages as you fix stuff...

subman60 · #5 09-07-2016, 12:18 PM

I'm aware of how a t-stat functions, but I have seen a few that wouldn't open all the way and would restrict the flow of antifreeze causing the engine too run hot. Since I was draining the system and it's easy to change why not. Plus I wasn't sure which temp stat was in it. There are no visible leaks and no antifreeze in the oil. If I can find a new cap locally I'll change it today and will clean the outside of the radiator and condenser today. I've never done a chemical flush on a cooling system but could it possibly help bring the temp down?

Rogviler · #6 09-07-2016, 12:40 PM

It's possible that the radiator is plugged internally, in which case a flush of some kind might help. I tried a bunch of different things on mine, including a flush, before I figured out the leaves thing.

But all anyone can do on here is armchair quarterback, so check out what I suggested and then you can move on to the next cheapest and easiest thing. For instance, making sure the fan operates correctly (which you'll have to look up as I always forget in what way it's supposed to be easy or hard to turn).

-Rog

ESchwab · #7 09-07-2016, 01:17 PM

Have you checked your coolant level since you filled the system? Often on these coolant changes air is trapped in the system and does not permit a complete fill-up so that additional coolant must be added later.

When I changed mine last time, I had to add more than half a gallon after the initial "fill-up."

subman60 · #8 09-07-2016, 01:23 PM

I took it for about a 10 min drive after the refill. After it cooled of enough I checked the level and it was good. Though it does seem odd that the owners manual list it as holding 10.5qt and all I could add was 2gallon (8qt). Last night I figured it was due to having the car on ramps which left some in the block or heater core.

leathermang · #9 09-07-2016, 01:30 PM

How long have you had the car ?
Has this just started lately or is this one of those slowly increasing over time deals ?
you had the car on ramps to fill the cooling system so as to avoid that famous air pocket ... or does your car have the extra outlet which eliminates that problem ?

leathermang · #10 09-07-2016, 01:33 PM

Quote:

Originally Posted by subman60

I'm aware of how a t-stat functions, but I have seen a few that wouldn't open all the way and would restrict the flow of antifreeze causing the engine too run hot. Since I was draining the system and it's easy to change why not. Plus I wasn't sure which temp stat was in it. There are no visible leaks and no antifreeze in the oil. If I can find a new cap locally I'll change it today and will clean the outside of the radiator and condenser today. I've never done a chemical flush on a cooling system but could it possibly help bring the temp down?

Have you ever looked at how the MB thermostat is positioned ? very strange.. not that it would affect this situation.. but if you get a chance you should look at it...

I suggest you check the other more probably causes of overheating before doing the chemical flush... just considering probabilities.... as you have started doing....

subman60 · #11 09-07-2016, 02:11 PM

We have had the car about 4 years, bought it for my sons to drive. They never mentioned it. I noticed it when taking for a spin after installing new rear axles. It never reaches the red on the dial but gets too close for comfort with the AC on or on the interstate. If you drive in town and leave the AC off it sits at about 100c.
I had it on ramps to make it easier to get under if I needed too. I will need to pull the t-stat just read that there should be an arrow on the stat that should face a certain way. Didn't catch that when reading the other material before performing that task. What problems can that cause?

BWhitmore · #12 09-07-2016, 04:22 PM

If the thermostat is not positioned correctly it could prevent the t stat from opening fully. As suggested, you might want to invest a few dollars and buy an infrared heat gun just to check the accuracy of your temp gauge.

leathermang · #13 09-07-2016, 05:54 PM

Quote:

Originally Posted by subman60

..... should face a certain way. Didn't catch that when reading the other material before performing that task. What problems can that cause?

If you are just talking about the ' clocking of the thermostat ' then I think the difference is that a small hole is placed at the top so that air can escape.. it keeps there from being an air pocket there....if you mean actually backwards... insertion.. I do not know...

subman60 · #14 09-07-2016, 11:30 PM

Is the 240d suppose to have a fan clutch? Because this one doesn't have one. The fan is bolted to the pulley. I cleaned the outside of the radiator and condenser but didn't pull the t-stat, to hot today to work out side.
I looked at the old t-stat it didn't have any markings on it to show how to install it. But have a feeling it may not have been installed right. Can anyone tell me how it should be oriented?

vstech · #15 09-08-2016, 07:10 AM

Pointy end towards flow to radiator.

The 240 radiator is easy to clean out, or at least to see if it is plugged up in the center. How does it look inside?