I have an 07 Type-S MT with approx 121,500 miles. I bought it certified from Acura in March of 2012 with 73,000 miles. Since I have owed the car the coolant has had a slow leak. I tried to get Acura to fix it while certified and they said the "pressure were fine, there is no leak" which I thought was bogus because I was adding coolant but whatever. When I bought the car it had blue coolant so I'm assuming it was Honda Type 2, and that's what I've always used to fill it up. The leak is slow, I added about 1 gallon of coolant over the course of a year. I have never had any over-heating problems, engine problems, everything runs perfect (as far as I can tell).

The other day I went to add coolant because it was just below the "MIN" mark, and I noticed that there was a layer of dirt inside where the coolant had been. I kinda freaked out because I don't know how my coolant could be that dirty. I had the 105k service done at 106,000 miles by a trusted shop, and I thought they would have replaced the coolant (but maybe they didn't). Anyway, I decided to drain the radiator and remove the reservoir to clean it. Well there was like 1/4" - 1/2" of sediment/dirt in the bottom of the reservoir. Also, the coolant I drained from the radiator was cloudy and dirty. I poured 3 gallons of distilled water through the radiator to clean it out, and it came out (1) really cloudy, (2) semi cloudy, then (3) mostly clear. I didn't have time to drain the engine block, so I know there must be dirt in there too... This really worries me. I am completely stock, so no CAI. I use the Acura air filter. Could a small leak in the system cause that much dirt to get in over time? I'm sure coolant shouldn't really get this dirty, but could it if it has never been changed? I live in the suburbs of Memphis, TN, and it is not a dusty environment at all, and I haven't driven through a dry baseball field or anything like that, so.... I'm at a loss.

See the pictures of the reservoir and radiator below. You guys have tons of experience and knowledge, and I have learned a ton about this awesome car and DIY maintenance from reading on this site, so I figured this is the place to come for help. Thanks!





Layers inside of reservoir




Dirt around radiator neck

 

Someone might have added that radiator seal powder BS and probably a lot of it, it's a quick fix but harsh for the cooling system parts in the long run. Best you can do right now is try to determine where your cooling fluid is going. Check oil condition to make sure it's not mixed with the coolant. Check exhaust when you start the car, white smoke, sweet smell. Clean engine bay the best you can and try to locate the leak, if it's external.

 

Thanks for the reply tk2k6. I have changed the oil myself since I've owned the car, nothing out of the ordinary. I changed the oil about 1,500 miles ago and everything seemed fine, and I checked the dipstick while draining the radiator and nothing was foamy or weird looking. No white smoke at startup. I can smell a sweet smell sometimes but that's from the engine bay where I figure the coolant is hitting hot spots. I wondered that too about the radiator sealant stuff, but why have I never noticed it until now? The "debris" just seems to be extremely fine dirt, almost like dust. It was muddy brown. Didn't seem to be the leak stop stuff which is usually a metallic color right?

 

Can you smell this sweet smell inside or outside of your car? Try turning the heat all the way up inside slow to med fan?

 

It's only outside of my car. I've never smelled it inside, even with the heat on.

 

You definitely seem to have a leak if you're losing a gallon of coolant over the course of one year. I would rent a radiator pressure tester from your local auto parts store (Should be free to rent) and pressure test the system. It is very easy to use and should 1) help you locate any external leaks emanating from inside the car or around the radiator/hoses/engine, or 2) if you are seeing a pressure drop and there are no external leaks, then there is a fair chance you have a leaky head-gasket. If you pressure test your radiator, just be careful not to over-pressurize. The pressure range should be between 14-18psi. Hope this leads you in the right direction.

 

Is the brown stuff oily? Like engine oil

 

It is not oily at all. It is just like a very fine grain brown dirt/dust. Not rusty red either, just a medium brown. It was basically mud in the bottom of the reservoir. No one I've talked to knows how it could have gotten that dirty. Also, I checked the engine oil on the dipstick and it is fine. I changed the oil about 2 months ago and nothing abnormal.

I'm pretty sure the radiator itself is leaking. I was looking around and I can see a little bit of blue liquid around the driver side base of the radiator. Like I said, I've known the sytem had a leak, and I eventually will replace the radiator (if that proves to be where the leak is). I just don't know how that much dirt could have gotten in there. I will get a pressure tester and see if that helps me.

Would I 100% be able to tell from the engine/oil if it was even a just small head gasket issue? Everything is running perfect, start up is fine, power feels normal, and I've had zero over-heating issues. Oil seems perfectly normal. I know what a bad head gasket is like on start up because my old car had an issue. Rough idle, white smoke on start-up, then it evened out as the car warmed up.

Thanks for all the replys. Keep em coming if you have any more thoughts!

 

If it is a small leak, it may be difficult to tell if your head gasket is leaking other than the obvious signs of white/sweet smelling exhaust, coolant mixing with your oil, oil mixing with your coolant, or witnessing air bubbles in the coolant from the cylinder combustion/compression gases. Get that radiator pressure tester, and confirm your radiator is leaking as you suspect. If it is leaking, then replace it and perform another pressure test to see if you have an internal leak that may indicate a leaking head gasket.

Edit: As far as the mud is concerned, like tk2k6 stated, it's very likely that someone previously had poured in a heavy amount of stop-leak product in an attempt to plug the leak. Regardless, I would flush the entire system to make sure you get all of the engine coolant passages, hoses, and heater core cleaned out.

 

Maybe it is some kind of stop leak chemical that is falling out of suspension or coming lose from inside the system. That does make sense due to the leak that was there when I purchased the car.

Would this be a time that I actually need to do a real flush with a machine (which I've heard is not usually a good thing to do)? Or by flush do you just mean drain the entire system/engine block, run distilled water in it for ~30 minutes, then refill with coolant?


I'll also get the pressure tester and see what I can figure out.

Thanks again for all the replys.

 

I believe circulating distilled water through the system would work well to flush out most of the gunk and debris. After the lower intake manifold gasket on my old 2000 Grand Am made the decision to allow the dexcool to enter into and contaminate the oil (evidenced by milky-oil substance underneath the oil-fill cap), I flushed out the coolant system with distilled water and I found it to be effective.