I just read about a UV dye that can be added to engine oil to hopefully make tracking down oil leaks easier. Anyone have any experience with a product like this, either good or bad? My M 272 engine has 150,000+ miles and im finding oily stains in a few places.

- Oil filter housing and cooler assembly, going down the front of the engine. I'm thinking the gaskets are worn. I recently cleaned with degreaser and monitoring area.

- On intake manifold. along the valley below the fuel rail, between injectors.

- Slightly dirty below crankcase breather cover passenger side. recently replaced cover along with drip pan. Oil in breather hose, put back for now. Caps look fine, dry.

- On/around/below throttle body. I plan on removing MAS and elbow at throttle body to thoroughly clean everything. Also could be coming from air/oil separator cover and hose, no visible leak at separator cover.

I have no idea how long the oily stains were there, i just never really noticed or looked that hard before. Now I am, so I notice everything. I changed the oil a few months ago and the level seems about the same. Im guessing oil may be coming from old worn gaskets, so i would like to find where. I did replace one or two canshaft sensor o-rings where I noticed oil staining. Its things like that I am looking for. I figured a UV dye would make the oil leaks stand right out. Anyone have experience with it? Reviews seem good, except for one where the guy says it turned his oil into mud. Love to hear anyones experience or recommendations. Was also thinking of throwing a bottle in the transmission during my upcoming trans service since I noticed some staining while under there.







Oil filter housing. I cleaned it up a little and monitoring.


Front passenger side of intake manifold.



Front passenger injector. All 3 look like this to an extent. It seems hard like carbon build up.



This is an example of the "wettest" oil staining I see. Scraped the gunk with a screwdriver.



Little oily at top of the throttle body. Could this be coming from air oil separator hose?


Lower right side of photo above.



Looks dry.

At cam plug.


Staining at rear of transmission.


Fluid on rear of trans.


Sprayed degreaser and hosed it down to monitor for leak.


At plug for torque converter. Oil or trans fluid?




Is this just from a high mileage engine? Id like it to last a million miles if possible. Trying to address everything, within reason. As I said before parts are relatively cheap but they are starting to add up.

 

Yes. It works. But most of your oil spots look like seeps and not leaks except for maybe one. That’s the oil on the torque converter access plate. And that’s just the place to use UV dye to diagnose if it’s engine oil from the rear seal or transmission fluid from the front seal. Clean it up, then add dye to the engine oil and drive for a few weeks. If it fluoresces with the UV stick, then it’s engine oil. If not it’s transmission fluid. Either of those leaks can get serious.

At 150k miles, valve cover and oil filter housing leaks are not unusual, but if they’re leaking to the point of dripping, they’ll be oily without the greasy gunk buildup. UV dye would only help there if the source of the leak were uncertain. Leaks at the rear of the valve covers can run down the back of the engine and the dye can eliminate or confirm the rear main bearing as the source.

 

Not sure if your transmission has a dipstick or if it is the 7G 722.9 seven-speed. Since probably the latter, I would only be concerned about a transmission leak since you should be periodically checking your engine oil level anyway. Yes, the engine looks dirty, but it don't care. Degrease it from time to time if you wish, but your car is 13 years old with a bunch of miles. Any fixes may give you peace of mind, but unlikely will make any difference in longevity of the car. I have 250,000 miles on my (now my son's) 2004 Audi TT and it gets a little oily. But as long as the engine oil level is good, I'm not apt to try to fix every seep or leak.

 

I dont see a dipstick, there is only a black rubber cap looking thing on the top in the engine bay. Looking at a parts diagram it does show a "seal ring cover oil filler pipe", but when i look at photos on ebay of 2010 C300 4matic transmissions the is a round electrical connection looking thing at this are, nothing that looks like a plug for a dipstick.


Diagram for 240.081
I do see part#250 Screening Plate though.

I do enjoy cleaning things and having things look as good as possible. I have a 1971 Ariens Sno Thro snowblower that I completely dissasembled this past winter, cleaned everything down to every nut and bolt. I do this with everything, Bought a used weed wacker and i took that thing completely apart so i could clean the entire thing. Its satisfying to me.

With this car I'm always cleaning it, I live right on the water, my car is parked 10 feet from the ocean at high tide. Im on the bay side so no waves thankfully. The salt water is pretty bad, leaves a film on everything. I wash and apply the Turtle Wax Wet Wax weekly, that stuff is great and takes no time to apply since i dry the car with microfiber towels anyways. For the engine bay I have a spray bottle with a little maguiars Gold Class car wash soap and water and ill just spray and wipe everything visible whenever im under there. I dont really touch the engine itself, thats more of a corrosion and doesnt easily clean off. Reminds me of barnacles on rocks for some reason how it looks.



These oil stains are different though, they are all hidden out of sight so cleaning for looks isnt the concern. I have no idea how old they are or how long they have been there. Most look more dirty, not oily dripping wet. Figure i can clean them a bit, take photos, then come back later and take more photos so i can compare them on my computer screen to gauge how bad they really are. Oil getting into the intake manifold I read can cause issues so its up on my list. Last thing I want to do is spend money without having to, half the reason i work on things myself is im cheap and hate spending money. I recently replaced the breather cover and drip pan, but im a little upset i bought the drip pan because the old one does look fine to me, no wear really.




The cover did need to be replaced, oil is in the breather hose and the gasket was worn looking compressed down flat. I plan on just cleaning most things, like both breather hoses going to throttle body, but debating whether to replace the air oil separator cover since thats not leaking. I was going to buy mass air flow sensor cleaner but now not sure if its a good idea to even mess with it, think ill just remove it to get to clean the elbow below it and throttle body.

Im just not sure what has already been replaced. Example the thermostat does appear newer, cleaner than the surrounding engine.



The vehicle does show it had front end damage at some point. Carfax does show it was taken to mercedes dealers in the past. So far I have yet to find any aftermarket parts, everything seems to be mercedes parts.




I write down everything ive done to it. Just scribble notes as i go.





The fluid underneath I have no idea how long its been there. I never looked under until recently. When I removed the plastic undertray I did clean off some gunk, it wasnt wet but more like old dry grease. I did not look like fluid was actively dripping. At that cap to access the torque converter, is that filled with fluid? If i pop the cap off will trans fluid pour out? I have no idea, never worked on a transmission before.

I saw that uv dye and thought what a great idea, put it in, drive around a week then just look around with a uv flash light at night for any leaks to pop. And its only about $7.

Side note if anyones interested Mobil 1 has a rebate on 5 quarts. $6 on there regular and $10 on extended. Walmart has the 0w40 for $26. cant use it for Amazon though.

 

Since oil can travel quite far from the actual source of the leak, the dye is the best way to determine where the leak actually is. That's what my SAE member father taught me about diagnosing an oil leak. He also taught me to make sure to keep the engine bay clean because dirt build-up in the engine bay can get into electrical connections and cause all kinds of trouble. Also a layer of dirt will cause your engine to run hotter than it should which is also not good. You also live right by salt water and the salty air is really damaging for your car.

 

I was at first thinking valve cover gasket leaks. I searched around to see how much gaskets will cost and all i was finding was a sealant which was odd. Finally I came across a video showing there is no gasket, it is a sealant. What a nightmare. Thankfully i checked all around and the no oil or staining along those joints. I just ordered the UV dye after reading the positive info about it here. thanks.

 

Can anyone tell me where this "Camshaft solenoid Harness" part# 2711500156 would be installed? I saw it on FCP. Wonder if i already have it, or if its something to get since it isnt that expensive.

 

Ordered the 1oz bottle of UV dye which was $6.79. I also found a pack of 2 black light flashlights for $6.99. Get $1.50 digital credit for choosing Prime delivery day also. Very excited to get this in the engine and see what it shows.

 

Found those harnesses. Doesnt look like they came like this with the car, looks like they were installed afterwards.

 

If the photo of your car is recent, congratulations, it looks great .

Since you are looking for source of problems, please look at the rear subframe, it is prone to rust and since the car seems to be in the NorthEast, the more likely to rust. See attached letter.

On the oil in the engine room, clean it as much as you feel satisfied with it. I keep the engine bays as clean as I can possibly do it. Not showroom quality, but clean enough to put my hands in it w/o having to look for my "mechanic clothes", and skip gloves because I can clean my hands easily on soap. I do appreciate when others do as well, in particular when they are stranded and I am offering a hand to help.

 

Thanks for the info. After I bought the car I had a front spring break while parked overnight so replaced both struts and decided to replace the rear springs since they looked rusted away at the bottoms. While under there I noticed the spring control arms rusted too so was just searching around on how to replace and i came across the subframe rust issue. Thankfully it looks ok, there is some rust at areas but nothing that stands out where it should be replaced or unsafe to drive at all.










Ive had good luck finding inexpensive used Mercedes parts off ebay from Cali salvage cars. Such a difference between New England parts and Cali parts. Think I paid around $125 for a pair of front struts with 30,000 miles to replace my rusted 120,000+ miles struts. Set of rear springs were around $35-45 shipped i cant remember, those looked almost new. I want to replace the srping control arms so bought 1 used single and then a whole set of the drivers side control arms, bushings look great. Bought a complete drivers side wheel carrier dirt cheap to use the dust shield and e-brake cable. My dust shields were so rusted away the brake pad springs wouldnt hold anymore. Ended up getting the other dust shield at the dealer for $11. Install was easy with just snipping away the old shields and cutting the new shields in half to fit behind the hub, didnt have to mess with taking all that apart. One of the spring control arms had a few scratches so i painted with some epoxy roll bar and chassis paint just for fun.





On ebay I recommend the seller labur-parts, bought a few things from them. Listings have alot of clear photos and they usually list the mileage of the parts if not the vin to look it up. Ive had luck lowballing in best offers, within reason.

When i got the car there were swirls everywhere. I bought a da polisher and learned how to use it, never used one before so it was scary at first. I use the maguiars ultimate compound with orange foam pads. What helps is I think the Mercedes paint is considered on the harder end, takes me forever to get swirls out but saves me from ruining the paint. This year I bought a clay towel, the nanoskin medium grade 7x7 towel and its amazing, makes the paint so smooth. I did buy an inexpensive fine grade clay mitt and while that did work it took forever and still didnt get everything off. Wash with the maguiars gold class soap and i was applying the turtle wax seal n shine for the past 2 years but this summer i tried the turtle wax ice wet spray wax and that stuff is great in my opinion, takes no additional steps or time to apply since you spray it on while drying off the car with towels. I took that photo of my car after i used that spray wax for the first time. I dont spray it on the glass, i like the glass totally clean with nothing on it so the wipers dont skip around.

 

I went ahead and removed the mass air flow sensor and the elbow below it to clean then and see if theres any oil in the throttle body. It was surprisingly simple and now the wire clip that snaps over the top of the air box in the back fits much better, actually tight and snaps in place where before it was kinda loose. There was a little bit of oil/gunk in the breather hose and in the bottom of the elbow but nothing in the bottom of the throttle body. It does look like there is some oil staining on the top of the, i think its coming from the hose that goes to the air oil seperator. Cleaned the elbow and breather hose in the sink with dish soap and dried. Started to clean around the throttle body but was getting messy, going to get some engine degreaser and clean it later when everything is back installed.




The dirt in the bottom of the throttle body I think got in there when i removed the elbow.
Looks like oil staining on the top part of the flap that opens and closes.


I removed that hose from the top of the throttle body and instead of it being white like in photos of new hoses i see the tube was brown oil stained. I removed the air oil seperator to look under it, there was a little oil under there but noticed a small hole where the oil must drain back into. Put it back for now, thinking ill replace it and maybe even the hose.

I keep seeing what looks like a rubber type coating or sealant, its on the intake manifold at the front and rear upper corners. I have no idea what it is, im not seeing anything like it in other photos of intake manifolds i see.


Its black and somewhat soft, can press it in with my fingernail.

I feel much better not seeing an oily mess inside the throttle body. Not so worried about all the gunk.

 

Just posting more photos i recently took while looking at the old breather cover and drip pan i replaced. the round gasket the drip pan fits through in the cover doesnt look that worn, neither does the shaft on the drip pan. But somehow oil was getting past into the breather cover down the breather hose. i fit them back together and they do feel tight, def not loose moving around. The one thing that stinx is the gasket for the cover itself is very soft and now flattened, seems it should have been made better in my opinion. Looks like if you remove the cover theres no way to put it back with at least replacing that crappy gasket. Unlike the air oil separator cover on the drivers side, that gasket seemed much better, i was able to remove that cover and put it back with no issues, the gasket looked fine.





Flattened old gasket.



No way to reinstall the cover due to crappy gasket. Wouldnt even stay in place.


Can see oil down in the tube. Also some type of sediment, could be from the gasket being worn down.







Shame they dont sell just the gasket like other mercedes covers ive seen. I probably would have just cleaned everything and put them back.

 

You need to change all of your rubber gaskets because rubber deteriorates over time. Rubber can have tiny cracks in it that you can't see. You'll be back doing this same job in no time because of the deteriorating rubber. It's better to change the rubber gaskets now instead of having to do the same job twice. That's what my SAE member father always taught me about rubber gaskets.

 

I should have used the UV light to look everything over before I put the UV dye in because im seeing glowing areas that are clearly old stains and not new. I think i did pinpoint at least one location where oil has leaked/blown out and thats from a joint in the intake manifold itself, above the gasket where it mounts to the engine. using the light and seeing the staining glowing green makes it very obvious. I added the dye and drop around 80 miles and dont see anything new, nothing from the dye i just added. I did take a clean paper towel and wiped down areas and my oil cooler gasket is def leaking, no dye in it but it was a nice big wet drop which obviously happened since I had cleaned that area off a few weeks ago. I dont see any oil below, on the drive belt or drips on the plastic undertray below so i dont think its leaking that bad, yet. Going to order the oil filter housing gasket and oil cooler gasket and do that repair this week, debating if i should buy a new coolant hose since I have to remove it. the hose itself is in good condition, want to replace it more for the o-rings but those are $9 each so for a few more $ can just get the complete hose.

I have a 5 quart bottle of 0w-40 and a jug of Zerex g48 50/50 coolant, is that enough to replace the oil filter housing gasket? I dont plan on draining the oil, but plan on draining the radiator before removing the thermostat and the oil filter housing. My book says the cooling system hold 5.1 quarts of MB 325 antifreeze, I think the jug I have is 4 quarts/1 gallon.

 

Took some photos, can see some of the oil staining glowing with the use of the UV flashlight. This is the area on the passenger side intake manifold below the fuel rail. To me this staining looks old, does not look like fresh oil.












Not really concerned about any of that. Just interesting to see.

 

Im curious what the 2 bolts in the oil filter housing are for. Could they be used to drain the oil and coolant before removing the housing? Looks like there are openings in the oil and coolant ports on the inside that would be opened if the bolts are removed.

 

I should change the name of this thread to the ask anything thread.

Just went on NAPA website since I notice they are always running "monthly sales" on some good stuff. Ive been waiting for the Zerex G48 antifreeze to go on sale again and it has so ill buy another jug since its due for a coolant flush anyways. Think ill drain the radiator, replace the oil filter housing gaskets, fill then run it a bit then drain and fill the radiator one more time. Zerex G48 50/50 is $13.99/gallon. The Techron is $5.49 a bottle which I like putting in the gas tank once in awhile.



Wondering if a vacuum tool is best to use to fill the coolant back up? The Steelman unit is only $20 and the cap for Mercedes is only $14.99 with free shipping on the Steelman website. I did buy an inexpensive complete kit before but returned it after seeing i can buy just the parts i actually need, no reason to waste money on all those other caps ill never use. They are odd type quick connects so I figured I can just swap out the quick connect for the new coolant suction hose with a barb type fitting or even short section of pipe and jamb a tube over it.





or Walmart has all the Steelman stuff also, same price except the pressure tester is only $22 instead of $69.99 on the Steelman website. Odd.





Or can i just refill the coolant through the holding tank or whatever its called? Worried about air getting trapped in the system.

 

You need to use MB coolant only. Non MB coolants are known to damage the plastic interiors of MB radiators. The various MB forums contain alot of these horror stories. You also need to use 50% distilled water with the coolant. Distilled water doesn't cause the interior radiator rust that tap water causes. You should also replace the rubber hose. You need to understand that your car is now at the age where the rubber has deteriorated to the point where it's causing leaks. That's why you need to replace it or you'll keep doing the same jobs over and over because of the leaking rubber.

 

I am 100% confident in using Zerex G48 50/50 in my Mercedes. When I look directly on the MB website for approved fluids the Zerex G48 is listed.



Says MB-Approval 325.0 right on the label. My owners manual says MB 325.0 Anticorrosion/Antifreeze.



I want the 50/50 specifically so im not wondering if its best to use distilled water or tap water, I have seen arguments for both. The Zerex comes premixed with deionized water. I dont really know the exact significance of this but from my limited understanding deionized water is pretty much just "pure water'.




I am buying the Zerex in this case because as I said it's on sale for $13.99 a gallon at the small hole in the wall local NAPA that I like giving my business to. If I could get the Mercedes labeled 50/50 for the same price then I would go with that, but even if it were only one dollar more I would go with the Zerex because I see no need to spend money that I do not have to.

I tried searching around if Zerex G48 coolant is harmful to Mercedes cooling systems and not coming up with anything. To the contrary people seem to be recommending it.

 

Here you are getting advice. MB coolant comes in different colors depending of engine model, and year. In fact, MB dealer must have your VIN before telling you which coolant to use. If they are that different I wonder how another brand can make one single fluid for ALL of the MB vehicles. Something sounds OFF already.

From other threads, I can see you have been working diligently on having your car in tip-top shape. Saving a few bucks with long-term concern from others, it is worth getting very clear information before proceeding. I have not changed the coolant on my cars yet, but I do not plan to play roulette with them unless I am 1000% certain which one to use. I have read that the new coolant should also come with a new MB coolant reservoir because there is a chemical package in the reservoir that matches the coolant.

Anecdote: A few years ago a relative's car (Jeep Liberty) needed coolant because of a radiator replacement. They got the wrong coolant in, supposedly some Zerez Chrysler Approved, and two years later the whole cooling system was ruined completely, rust everywhere. Not saying anything about Zerex, just picked the wrong Zerex for the car's year and that decision ruined the car later. What a mess it was.

 

I think I understand what you are saying. The Zerex G48 is NOT for all mercedes, it is only for the models that require MB 325 antifreeze, its the blueish green color. I guess the newer Mercedes require MB 325.6, which is pink I believe?

My specific 2010 C300 requires MB 325, verified in the owners manual. I also looked at what is installed and it is the blue. I was a little low before so bought a gallon of Zerex G48 and topped it off.


Photo of the operators manual in the glove box.

So i look on the Mercedes Bevo website and see this:




Then click on MB 325.0 and see this list of approved antifreeze:






Note there is not even a "Mercedes" antifreeze listed. I can find Mercedes 325.0 antifreeze online but it seems limited in options.

Here is the MB 325.6 for comparison. Note how "Mercedes is the 1st one listed.





Im most definetly on here for advice/tips and value everyones opinion and input. Hope i didnt come across in a bad way with my response. I would like an explanation of why something may be wrong or not a good idea, for my understanding if I am wrong. if im wrong in my thinking that the Zerex G48 is the correct antifreeze for my car id like to know where I went wrong in my research. That operating fluids website is a bit confusing in how they have the MB 326.0 sections which are labeled as Premixed. When i look at the MB 325.0 antifreeze they all say to mix 50/50 (distilled water). I actually had emailed Zerex support awhile back asking what is best to mix the concentrated antifreeze with and response was distilled if fine but tap is ok also, so thats when i said im getting the pre mixed 50/50 because I wasnt comfortable with that answer.

 

Oh, and I also read that new cars come with some type of silica pack in the coolant reservoir, and thats why they claim the 15yrs. I went ahead and asked around, asked FCP euro, Pelican parts, eEuro if any of the replacement tanks they sell come with silica packs and was either told no or they dont know. So from my understanding if a new silica pack is not installed then the 5yr/150,000 mile schedule is to be followed. All that silica pack does is extend the time frame. plus my cars over 150,000 miles now and the maintenance book says services are to be performed much sooner now.



Heres examples of what i came across when i was looking for Mercedes 325.0 coolant. Its why I got the Zerex idea from.

 

For my W201 which is your car's grandfather, I have to use MB coolant. There are many online horror stories from owners of MBs from this era using non-MB coolant and doing serious damage to their radiators. As for using distilled water, I was taught to do that by my engineer father who had bachelors and masters degrees in engineering, more than 40 years of aviation and automotive engineering work experience and was a member of the Society of Automotive Engineers. He taught me how to take care of a car and to only use distilled water along with coolant in a 50/50 mix. I think he knew a little something about the issue.

 

Just ordered everything I think I need to replace the oil filter housing gasket and oil cooler gasket. Spent roughly $76 with the majority of this cost being the oil and antifreeze. I did fill out a rebate from Mobil 1, $6 back from each 5 quart jug and they were $26 each. I bought the parts from eEuro saving money by buying the OEM gaskets and seals. i also had some points to use from a previous purchase so saved another $3.45. Basically just got the oil filter housing gasket, oil cooler gasket, thermostat gasket and thermostat o-ring and an oil filter. I got a couple engine block drain gaskets since they were only 5 cents, if I can reach it easy enough ill drain the coolant from the block also. Got some vacuum line just to have on hand. Was going to order a new coolant hose but figure its easy enough to swap out so ill wait to see if theres an issue when i put everything back, the hose does seem in good condition, may even be newer and changed at some point.

eEuro seemed to be the least expensive for most things and has a 2yr warranty. I like FCP because the lifetime warranty and they are in the next state over and i usually get my order then next day after they ship but are more expensive. eEuro has a $10 credit for signing up to there loyalty program and gives points for buying things.

https://eeuroparts.com/?wlpr_ref=eEuro_atc0xpy6j