So I have a 2008 G35.

The car never had any failure or issues.
A few days ago it randomly over heated, after a lot of oil changes and filling the radiator multiple times in 2 days, the diagnostic was that the water pump has failed.

as of now the car is with a mechanic( he’s a friend ) I was told the head gasket is fine cause the coolant didn’t have any oil, however the dipstick looks like milk.

Did anyone else go through this? Is this the beginning of engine failure and the start of multiple visits to the garage?

The bearings and tensioner look fine though.

i have asked the same questions from my mechanic but not safisfied with his answers.

Edit: this is my first post ever so please. Be kind.

 

Milky oil is almost always a head gasket failure, do a leakdown test and see if it bubbles from the radiator.

Typically the water pump doesn't fail, it's an incredibly robust unit on these cars and it will weep coolant for dozens of thousands of miles before it ever crapastrophically fails.

The usual cause of the overheat is failure to maintain coolant pressure (pinhole leak, bad radiator cap, etc), if it hit the high mark of the temp gauge it almost definitely warped the heads which then blows coolant into the oil passageways.

Ask him exactly how he verified the head gasket was not blown, if he didn't do a leakdown test then he didn't actually test the HG.

 

So basically the garages we have here ( the ones I can afford actually) don’t do those tests. When it over heated it didn’t reach H, however it’s not the first time it over heats.

upon opening the engine the mechanic sent me a video that shows the water pump leaking water.
the way he figured out that the head gasket wasn’t blown is because my car drove normally for about 100 kilometers after the first time it over heated and I changed the oil and fillies the radiator back up.

If I keep filling the radiator up it will just make the oil milky pretty much nothing else. If the head gasket was blown when I start the engine all the coolant will push out of the radiator ( when the cap is open).

i changed the caps a month ago so they are good.

I don’t know if I’m making any sense but I’m just worried for my baby .


do you think an engine change would be necessary soon or water pump change should do the trick.
thanks for replying

 

Too hard to say, post that video he sent you to youtube then put the link here and it will automatically embed.

I'm just extremely suspicious of the water pump leaking water out through the shaft seal, and I don't think it would be possible for it to leak at the engine block o-ring seal.

If it's weeping coolant out the side of the block that means the pump does need to be replaced, that's the factory intended way for you to know the pump bearing is worn to the point that the pump needs to be replaced. There is a little hole on the side of the engine block adjacent to the water pump for the coolant to drain out.

However a worn pump is still pumping water and is incredibly unlikely to crapastrophically fail, it's SUPPOSED to leak coolant from the side of the block when bearing thickness hits a certain threshold, it doesn't just stop working when it starts to weep coolant.

Also, about the leakdown test, this is LITERALLY the second most common diagnostic test to verify the condition of the long block, compression test and leakdown test. If your mechanic won't do a leakdown test to verify the HG before expecting you to pay for repairs to other systems then you NEED to find a new mechanic because that's a huge red flag of a shady mechanic.

It's a quick diagnostic, it will cost you 1 hour of labor, and if the HG is blown there's no sense in you wasting money on a new water pump since the engine needs to be taken apart if it's leaking.

There are many ways a HG can fail, oil to coolant, coolant to oil, coolant to cylinder. That he's relying on some flawed method of (well you drove it for 100km before it started puking water into the oil) is ABSOLUTELY NOT how to properly verify the head gasket. It will not always just push air into the coolant and make it bubble, though that is a common way for it to fail, you need to do a leakdown test to verify though.

To troubleshoot the overheating condition the first step is to pressure test the coolant system and cap to verify it's actually holding proper pressure. If you are weeping coolant then you would be replacing the pump regardless (as long as the HG is intact) but you might have other components that need to be replaced/repaired too due to not holding pressure.

Proper troubleshooting saves the customer money in the long run, randomly throwing parts at a car hoping it will fix the issue is the most expensive way to "diagnose" car problems especially when you're paying shop rates. Any shop that won't properly diagnose the problem and would suggest throwing parts at the car is basically just screwing you over in the long run.

Personally I can compression test, leakdown test, and coolant pressure test an HR engine all within one hour.

 

So i got my car back and it was actually the water pump. I saw the old pump and it was broken on the axis ( i cant really explain well ). it was leaking not from the O rings but the whole thing was broken. now the car seems to be fine ( a bit more powerful than earlier). Engine oil seems to be TOO CLEAN, like i drove 1000 kms and it looks like new, coolant isnt going down anymore either.


i guess im the one in the million whose water pump actually broke.

 

Ok well that solves that issue, shaft itself broke and the shaft seal was leaking. EXTREMELY uncommon but it can happen.

Fortunately since you caught it quickly, repaired it quickly, you shouldn't have any major damage. Sure the bearings will take a little bit of a hit from being lubricated with coolant-mixed-oil but it's probably going to be fine.

I would definitely be checking that oil every few days though, particularly after a few good revs like highway onramps just to verify it's not pushing coolant past the HG.

 

i am afraid of the HG leak but it seems to be fine after about 1200 kms ( i drive alot). no milky oil actually the water seems to have cleaned the engine and its performing a bit better also not making the oil as dirty as i expected, just gonna do a radiator flush now and i should be good to go.


btw is it cool if instead of properly burping the raditor i just drive a bit wait for the coolant to go down and then fill it up afterwards ?
( getting the air out of the system is a pain )

 

Yeah getting the air out can be a pain, You might consider just paying a shop to do a coolant drain/fill then it's their responsibility to make sure it's done correctly

It's also perfectly fine to drain/fill incrementally over time, instead of doing a full drain just drain out like 1/2 gallon of coolant and then fill it up again, do that again a week later.

It's easier to just do it all at once but if you're worried about the burp then doing a couple partial replacements over time is perfectly fine.