possible bad head gasket, NO symptoms

Well, minus the funky coolant. Wife's radiator failed on her '02 Montero Sport a few months back, the shop mentioned that we should have the coolant flushed/filled when we next got the oil changed. I dutifully brought it in as requested, and they tell me we may have a blown headgasket or other internal sealing woes, as the coolant was pretty funky, particularly to have been new when the radiator was replaced a few months back. The service manager said they used the chemical dye test to look for hydrocarbons in the coolant, and it was a positive test.

I guess I just want to consult the hive mind and see what folks think- it runs fine, idles fine, doesn't get hotter than it should, I'm not seeing any evidence of smoke or condensate out the exhaust, there's just the problem of the coolant being all yummy Wendy's Frosty looking. The only problem we've had with it in ~7 years is that the idle control sensor in the throttle body needed cleaning. What am I missing? As much as I don't want to spend a big bunch of money on a repair bill on this thing, I also don't want to trade into a new car- this one's been pretty decent overall and is otherwise holding up like a champ.

Does this model have a trans cooler integrated into the radiator by any chance?

I'll have to look- I don't think so, the towing package IIRC included a trans cooler with the hitch, and for some reason (we were dumb kids, I think) we didn't get that added at the dealer when we bought the thing.

No symptoms? The coolant was kind of nasty a few months back. The coolant is now much more nasty. The shop tested the coolant and said you have a failed head gasket. Whether they're properly diagnosed or not, those ARE symptoms.

Whoever told you a bad head gasket causes poor running/idling, overheating, smoking, etc. wasn't lying, but there are other symptoms possible such as oil in the coolant. Just be glad you don't have coolant in the oil, as that indicates bearing DOOM.

Bryce

A bad head gasket doesn't have to cause poor running. Many times you just get what you got. You can be semi-fancy and use a test strip to make sure that it's combustion gasses in there. Redneck technique is to warm it up by driving, let it idle in the driveway, pop the radiator cap and notice if the engine changes it sound.

There is a pretty durn good chance you do have a blown head gasket. Though with your vehicle, don't discount the possibility of a blown intake manifold gasket. I'll let the GM experts on the board comment on whether yours is one subject to this failure or not.

Three Words

Leak Down Test.

Just what I was going to say. If it has an automatic transmission it has a cooler in the radiator.

Leak Down Test.

Lets look at this, you may have a bad head gasket. If so, the combustion chamber is pumping gasses (compressed gasses) into somewhere. If the bad spot is near the cooling jacket you get the higher pressured combustion into the radiator. Oil can get pumped into the cooling system causing the brown jizz concoction.

If it's a crack in the block or it crosses to the exhaust chamber, you can smell sweetness in the tailpipe.

Are you losing coolant? Losing oil?

Use your senses, smell, touch.

Do a leak down.

I was hoping somebody would come up with some magical reason as to why I have a milkshake going on in the radiator, thassall. I guess I'm in denial. Oh well, we'll probably just fix it and soldier on- I am aware that if it still runs right and all I have to do (knock wood) is get the gasket repaired, I'm getting off light.

Unfortunately, this falls into the "would take me a month of Sundays to do, so I better pay somebody" category, too, so the ol' bank balance will feel it. Arg.

foxtrapper wrote: Redneck technique is to warm it up by driving, let it idle in the driveway, pop the radiator cap and notice if the engine changes it sound.

Uh do you mean coolant tank cap? Wouldn't this cause a horrible eruption of boiling hot liquid?

Hmmm. Cooling systems run at 13 or so PSI, oiling systems run at 20-25 PSI and up. Oil in the coolant (that's the chocolate milk) with no other real symptoms tells me high pressure oil is being forced into the lower pressure cooling system somewhere or other. The most logical place is the head gasket(s), although there are other places (like timing covers on chain driven OHC engines, although this usually buy not always means chocolate milk on the dipstick as well). And as noted yes it's quite possible to have a bad HG with no real effect on driveability. Those are tough to diagnose.

Um, ew. Went out to look at it and see what else there is to see. Coolant looked OK at the filler cap, though there was a tiny little bit of brown to be seen floating atop the green stuff. The overflow tank, however, not so much. Milkshake is charitable, that would have to be described as more like baby poop. I think, as you guys have said, that wherever it's getting it, oil's getting pushed into the radiator. Last time I pulled the dipstick before this oil change, it was about a quart low- oil in the coolant would at least explain where it's going if it's not marking its territory or smoking up the road as we drive along.

Stay tuned for the riveting details of what kind of goo shows up over the next few days.

It's official, by the way, that this is now my car, we'll be trading the Mazda3 wagon up for some other peoplehauler for the wife to drive.

Also, you guys are awesome. This thing has about as much sporting potential as a school bus, and yet I get help thinking through it. Thanks!

if theres milk shake in the rad and the oil is clean, pull the lower intake and be very careful when you get to the gaskets, try not to destroy them(just so you can inspect them) the coolant port/passage 50% of the time fails, when the engine cools down the failed gasket allows the engine to "suck" the oil in, i just did the inlaws for this exact reason and thats what i found hth

if theres milk shake in the rad and the oil is clean, pull the lower intake and be very careful when you get to the gaskets, try not to destroy them(just so you can inspect them) the coolant port/passage 50% of the time fails, when the engine cools down the failed gasket allows the engine to "suck" the oil in, i just did the inlaws for this exact reason and thats what i found hth

Something to look at. I kind of wish this wasn't one of the "need this every day for hauling kids" cars, otherwise I'd be tempted to try my hand at pulling it apart and sticking some new gaskets on.

The wife's people hauler had a lower intake manifold fail (thanks GM). The radiator and the crank case had the same crap in them. Looked like baby poop. Twelve hours later and much cursing I hit the key to have nothing. No compression on all 6 cylinders. Thought I had put the push rods in backwards. Checked them and they were correct. Kept trying it and it finally started. No problems since, but I cringe every time I check the oil.

I have seen more than one in radiator trans cooler fail and leak trans fluid into the coolant, you really need to check the trans fluid level and condition if this does in fact have a trans cooler in the radiator. Also an effective shade tree method of detecting a had HG on an engine that is still running ok with few symptoms is to see how quickly the cooling system pressurizes when the engine is started up from being completely cold. If the pressure starts building up right away, the HG is leaking compression into the cooling system.

Bump-

Wound up not being the headgasket(s)- a coolant pipe somewhere in the intake manifold was slowly seeping coolant (warpedredneck wins!). $200 fix instead of $$$$, I'll take it.

the small amount of brown-ish crud in the radiator, I'm told, is probably just more corrosion from inside the engine washing out as we put new/fresh coolant in it. Any thoughts on those Prestone radiator back-flush kits? Do they work as advertised?

its going to be hard to get all the pockets of oil out of the cooling system, i personally drain the cooling system, fill with water and 1/4 cup of tide, run it for 20 mins, then drain/flush with water, run 10 more mins, final drain and fill with new coolant/water mix

HappyAndy wrote: I have seen more than one in radiator trans cooler fail and leak trans fluid into the coolant, you really need to check the trans fluid level and condition if this does in fact have a trans cooler in the radiator.

Mine went the other way... pumped coolant into trans. I had a strawberry milkshake in both trans and engine by the time I noticed. I noticed because the truck stopped shifting.

canoe