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Discussion Starter #1
Hello,

We just purchased a 2008 Cab with 50K on it. Just noticed a small puddle of the blue coolant under the front of the car closer to the drivers side if the car. Does not appear to be leaking so much that the coolant reservoir is too low and does not seem to be directly under the radiator. However I suspect it is leaking onto the plastic pan under the front end so it could just be leaking across the pan and out onto the floor. Any ideas? I know if it is the radiator that is a significant job labor wise but am wonder if it could be a bad hose or something less dramatic to deal with right after buying the car! Hoping it is not worse though than the radiator!

Oil looks clean and clear and no smoking so appears to be just a leak of sorts...

Thanks for any wisdom and advice...
 

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Welcome to SCoA! The coolant lines run under the car from the engine up to the radiator. You'll have to remove the plastic underbody tray to get at them and find the source of the leak. :)


1 Radiator
2 Expansion reservoir
3 Coolant return line
4 Coolant feed line (large circuit)
5 Coolant pump
6 Coolant pump belt pulley
7 Thermostat
8 Coolant feed line (small circuit)
9 Heater heat exchanger
10 Coolant pipe
B11/4 Coolant temperature sensor
M4/2 Coolant fan motor
 

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Discussion Starter #3
Thanks for the quick response and the excellent diagram! Wow this could be a bit more complicated than I hoped!
 

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Discussion Starter #5
It looks blueish in the reservoir but it is hard to tell looking at it on the floor also I am a bit blue green color blind so it could be me, I would rather it be a washer fluid leak! seems to be dripping under that under body tray.
 

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I would think it more likely it was windshield washer fluid. Stick your finger in the fluid on the floor. Smell it and rub your finger and thumb together. The coolant smells different than the washer fluid. The washer fluid is alcohol and water. The coolant will have a distinctive smell and feel sticky on your fingers. I advise against a taste test.
 

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Discussion Starter #7
Thanks for the tip. I will try it when I get home this evening. I am hoping it is washer fluid instead of coolant! Both reservoirs are still full, coolant is a min level when cold. Washer is still about half full. Worried that the guy I bought it from just filled up the coolant to mask a leak so will check levels over the next few days to see if either reservoirs goes down. We only ran the car for about 30 minutes in the last couple of days so hard , good thing is the leak appears light as opposed to losing all the fluid.

Thanks for the tips and answers!
 

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Discussion Starter #10
Well, I checked again last night, it does appear to be coolant, looks like the MB colored coolant, blueish green. The reservoir is still above the min level but we have not run it much either, it looks like it is leaking above the underbody plastic cover behind the radiator. So I am thinking it is one of the coolant lines running to the back of the car or heater core? At this point , no lights have come on yet however since I bought it used from a private party they may have cleared any codes already. I am betting they topped the coolant off too before we picked it up as it appears to be leaking fairly well just sitting in the garage.


Any ideas or cost estimates I need to brace fore? I am in Pittsburgh, PA so it looks like this will be a Merc dealer item as I don't think the local garages will work on it. Thanks for all the input and help!
 

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First off... there is no "low coolant " light or indicator. the only warning you will get is when the motor is overheated! and then it is too late. If the leak is up front, it may be the radiator or the reservoir tank (or hose between them)

If it has been (or is) run low on coolant, it could develop an "air bubble" in the motor as the coolant hoses are lower than the motor and will not 'burp' the air bubble out. This will show up as the temp getting warm, or after it is too late, have a head gasket (or worse)leak into the cylinder causing oil and coolant to mix in the oil pan or in the cooling system. The motor will miss and run poorly. Since there is not a temperature gauge on the car, you can use a OBDII scanner and read the temperature

Best way to find the leak is to pressurize the cooling system and see where it comes out. Pressure testers are available from Amazon, and some auto parts stores will loan them out too.

There is a procedure for bleeding the motor (air bubble) by removing a hose on the motor to let the air out until coolant comes out.
 

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Discussion Starter #12
Thanks for the info! Bit scary not having coolant low lights or temp gauges! I will look to do the pressure test this weekend then. I see the rad replacement is a larger effort , one I would try in the summer but not in the winter as the garage is not heated and it is 28 degrees out this week! I will likely schedule a MD service appointment for this now and tell the wife the deal we got appears to not be such a great deal now! UGH!

Hopefully it is a simple hose issue and not the radiator. Will pick up some coolant today and make sure it is at the proper levels until it gets repaired.
 

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Thanks for the info! Bit scary not having coolant low lights or temp gauges! I will look to do the pressure test this weekend then. I see the rad replacement is a larger effort , one I would try in the summer but not in the winter as the garage is not heated and it is 28 degrees out this week! I will likely schedule a MD service appointment for this now and tell the wife the deal we got appears to not be such a great deal now! UGH!

Hopefully it is a simple hose issue and not the radiator. Will pick up some coolant today and make sure it is at the proper levels until it gets repaired.
Pay attention to what is going on while you are driving it prior to getting it looked at. If at some point the hot air from the heater goes cold or the radiator fan suddenly turns on when it should not be warmed up, that means two things. One, it means there is air in the cooling jacket in the cylinder head and the coolant temperature sensor is no longer submerged in coolant, and two, SHUT 'ER DOWN! Then let it cool off, fill with coolant, purge the air at the bleed hose on the cylinder head and get it sorted. Otherwise, expensive damage will result.

If you drop down the front of the plastic under-tray you should be able to see the coolant hose connections enough to see where a trail is coming from. If at any point somebody has replaced any of the crimp-type hose clamps with a screw-type they may just need to be tightened.
 

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Discussion Starter #14
Thanks for the tips! Appreciate it, Will pull the under tray down to check before driving it again. Would be awesome if it is just a clamp issue! Will let everyone know once I find out. I did see another post about getting an OBDC II monitor for these cars. That would at least provide a warning sooner than losing an engine.
 

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Right after I got my 2008 smart, I picked up a ScangaugeII and set it up so I could monitor the coolant temp. With an aluminum engine, I am paranoid about it overheating. The motor is extremely expensive and you don't want that expense!!

There are a few other monitors that can be plugged into the OBD port and give you the readouts you need.
 

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Discussion Starter #16
Well friends, it turned out to be a hose clamp that was loose. Tighten it and so far no leaks. Fingers crossed. I am ordering a scan monitor just in case so I know of temp issues before I melt an engine! Thanks to everyone for the help and advice! Much appreciated the support and quick responses from this forum. I hope to contribute down the road as I learn more about this car!
 
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