Coolant being burned off

[mylamb]

Hello,

Does coolant combustion always mean you'll need a "new engine?" I have had a gradually increasing coolant loss for a while now. I had it looked at twice with no diagnosis. Then 2 months ago, the dealer replaced the coolant reservoir & a hose. That did not stop the loss. They found oil in the coolant but no coolant in the oil and flushed the whole system. They also pulled the plugs and found no problems with the head or combustions chambers. Yet, coolant needs to be topped off once per week. I occasionally (once every 2-3 weeks) get a puff of white smoke on start up or under WOT near redline.

There is never coolant on the ground or garage. I have never had the temp creep above the mid-range. I try to use the official pink coolant to top it off rather than water. The dealer said that if it's not leaking outside, and they checked the oil (and changed it) a couple of times then it is somehow getting into a combustion chamber and being burned off. There's really nothing they can do except wait for the problem to become more noticeable (I am not losing power) or wait for something to break. To do a teardown to look for the cause would be cost prohibitive (their words.) Is this some type of porous block? Is it possible that the engine has worn a hole in itself and is allowing oil & coolant to mix? Any thoughts or suggestions would be appreciated. I prefer not to be stranded or left with a dead car. I do have an aftermarket warranty but I would rather catch this than be forced to rely on their mercy.

2001 Boxster S

No mods

58,000 miles

Always serviced by dealer or P specialist.

08/03/09 Turned out to be a faulty oil cooler. Covered by warranty & it seems fine so far - coolant level is not dropping & is remaining bright pink. Will post if the problem continues.

Edited August 3, 2009 by mylamb

[Glyn]

Get the system pressure tested, you can purchase a simple hand type pump with a gauge for home DIY, pump the system up to 15lbs pressure then watch for pressure drop - if it goes down in pressure then water is being forced out somewhere.

My guess would be a pin pr**k type hole in the radiator which under pressure is expelling water - but so slowly that you dont get a puddle, If the water was getting into the combustion the oxygen sensors would pick that up and throw a code.

If it was me i would simply bung a can of stop leak into the system, though some Porsche purists would probably have a heart attack at the thought - but at the end of the day it is a car - with all the same problems as any other car

Edited June 1, 2009 by Glyn

[dr914jr]

I'd just like to say the term "coolant combustion" is the most awesome thing I've seen on the web all day. :lol:

You should really have the system pressure tested with the plugs removed. Than you'll be able to smell the coolant at the plug hole. If it's not in the combustion chamber than you'll probably find an external leak while the system is under pressure.

[pk2]

You didn't mention you weekly mileage.

They should have done a leak down test , be surprised if they didn't. also sniff the overflow tank for exhauste fumes. Due to your service vigilance you probably have fresh plugs, A little trick I learned years ago is that a water guzzling engine also happens to be very nice, well washed leaky cylinder. This means look for a nice shiny plug next to 5 crudy looking ones. Don't know if they teach this in Porshe school.

You also, should see a hearty plume of white smoke at first startup. Also there can be a plume after abruptly letting off a full throttle

As for a porous block or worn out block I'd find highly unlikely. Also Be aware metal expands when hot. In the case of a cracked head for instance, it can pretty much shut itself off once the engine is warmed up. (goes to milage per week)

In favour of the leak theory, I've seen motors with external leaks that only show up when the water is hot and expanded and pushing at the door. However by the time they drip across the hot block the coolant evaporates to a degree. Doesn' explain oil in the water.

Me I'd go to your indie guy. THey tend to go more by experience and horse sence then a rigid factory prescription.

Regards, PK

[mylamb]

They pulled the plugs & found that each chamber was fine. Still, it has to be going SOMEWHERE. They're convinced the leak is not external. I probably just need a new set of eyes on it. There is another shop near my office that I can take it to for an additional pressure test. Yeah, I was always under the impression that coolant would foul the combustion process, but the dealer said that small amounts will burn off and that's why it's leaving no evidence. But small leaks rarely go away, they only get bigger...

[mylamb]

You didn't mention you weekly mileage.

They should have done a leak down test , be surprised if they didn't. also sniff the overflow tank for exhauste fumes. Due to your service vigilance you probably have fresh plugs, A little trick I learned years ago is that a water guzzling engine also happens to be very nice, well washed leaky cylinder. This means look for a nice shiny plug next to 5 crudy looking ones. Don't know if they teach this in Porshe school.

You also, should see a hearty plume of white smoke at first startup. Also there can be a plume after abruptly letting off a full throttle

As for a porous block or worn out block I'd find highly unlikely. Also Be aware metal expands when hot. In the case of a cracked head for instance, it can pretty much shut itself off once the engine is warmed up. (goes to milage per week)

In favour of the leak theory, I've seen motors with external leaks that only show up when the water is hot and expanded and pushing at the door. However by the time they drip across the hot block the coolant evaporates to a degree. Doesn' explain oil in the water.

Me I'd go to your indie guy. THey tend to go more by experience and horse sence then a rigid factory prescription.

Regards, PK

Yeah, they did a leak down test - found no problems with the chambers or the gasket. I have only had the plume of smoke 3 times - twice under WOT & once at start up. Since the weather improved here in Chicago in 2009, I have averaged 100 miles per week - most are short trips. The warranty doesn't cover seals & gaskets so I would be on my own with that repair. I actually had a small gasket leak back in late 2006 & had to pay for that - not insane - maybe $1500 or so?

[Dharn55]

I am just finishing reassembling the engine from my 996 after an intermix. It was a cracked head, cylinder #1, inner exhaust valve seat. I did not see it with the plugs and tubes out, not until I had the cam covers off and removed the tappet carrier. Then it was obvious. It seemded I should have been able to see it with the plugs and tubes out once I knew where it was, but I did not see it then.

I never had any smoke in the exhaust or any other symptoms except oil in the coolant and coolant in the oil. The crack did not extend to the combustion chamber and had no effect on compression or a leak down test.

The bottom line is that the dealer taking out the plugs and tubes and running combustion tests and leak downs can be meaningless. Next step, drop the engine, start with head 1-3, as this is the most commonly crarked head. there are also lots of other areas that can carcked and can only be seen with some disaasembly.

Now the good news is that you probably don't need a new engine, although the dealer would probably love to sell you one. I had my head fixed for about $500 and hope to have the car running this week. Keep me posted on what you find.

[pk2]

Thats really interesting what Dharn said and would fit the bill except you don't believe you have water in your oil. I can't how Porsche would miss it but some grey sludge on the inside of the case, places like the dipstick, oil filler cap or other high spots open to the inside of the crank case. PK

[mylamb]

I am just finishing reassembling the engine from my 996 after an intermix. It was a cracked head, cylinder #1, inner exhaust valve seat. I did not see it with the plugs and tubes out, not until I had the cam covers off and removed the tappet carrier. Then it was obvious. It seemded I should have been able to see it with the plugs and tubes out once I knew where it was, but I did not see it then.

I never had any smoke in the exhaust or any other symptoms except oil in the coolant and coolant in the oil. The crack did not extend to the combustion chamber and had no effect on compression or a leak down test.

The bottom line is that the dealer taking out the plugs and tubes and running combustion tests and leak downs can be meaningless. Next step, drop the engine, start with head 1-3, as this is the most commonly crarked head. there are also lots of other areas that can carcked and can only be seen with some disaasembly.

Now the good news is that you probably don't need a new engine, although the dealer would probably love to sell you one. I had my head fixed for about $500 and hope to have the car running this week. Keep me posted on what you find.

This is very helpful - thanks! How many hours do you think it takes to drop the engine & examine the heads? This sounds like a job for a good indy shop, as the dealers rates are now $155/hr. I will def keep you posted. I would prefer to "catch" this situation rather than be stranded...

[Glyn]

I think you are thinking of trying the most expensive option first, Pressure test the system, if the pressure drops and you cant see the leak keep on pressurising it - eventually enough water will be expelled that you will be able to see- perhaps even a water pump seal leaking along the shaft then being thrown by the pully system - that would show no water under the car - take the inspection plate off behind the seats and pressure test.

After the flush is there more oil in the coolant? If no then considering dropping the engine and pulling the heads at this stage is madness.

If yes - then perhaps

[mylamb]

I think you are thinking of trying the most expensive option first, Pressure test the system, if the pressure drops and you cant see the leak keep on pressurising it - eventually enough water will be expelled that you will be able to see- perhaps even a water pump seal leaking along the shaft then being thrown by the pully system - that would show no water under the car - take the inspection plate off behind the seats and pressure test.

After the flush is there more oil in the coolant? If no then considering dropping the engine and pulling the heads at this stage is madness.

If yes - then perhaps

That's the problem - they have already pressure tested it (it's been done twice - once by an indy back in 2008 & recently at the dealership.) They both came up with the same story "we don't see any leaks." Only now, I seem to be going through more coolant than usual & have gotten puffs of smoke on occasion (not the typical kind you get on start up.) I'm trying to get a handle on the problem before it gets worse, but the 2 facilities that I've been to are not cutting the mustard on a diagnosis. I will need to try a 3rd.

[JeTexas]

There was someone on here who actually had a problem with the oil coolers leaking. It resulted in oil in the coolant but no oil coolant in the oil. The oil was actually filling up her coolant tank though.

[Glyn]

Good point JeTexas - the oil cooler is actually a series of pipes that have water running around them to exchange heat, if a tiny hole occurs the oil under pressure would push into the water - however when turned off i would expect that the water being pressurised would push water into the oil.

Water in the oil will enable the development of "Mayonaise" inside the oil cap very quickly - check it out.

I cant believe that two garages cant find the leak but accept there is a problem - The problem is they just arnt very good at their jobs, a fault can be traced if the person who gets the job is vigilent and enthused and is proud of their work - many businesses are full of useless individualls who only go to work to socialise and moan - or individualls with delusions of adequacy.

Get a third opinion from an enthused garage

[juniinc]

+1

oil residue in the coolant tank isn't necessarily an indication of a blown head gasket. Seals fail in the oil cooler, allowing coolant and engine oil to mix.

Perhaps it is time to perform a oil cooler pressure test,,,

http://mx.truveo.com/996-Oil-Cooler-Pressu...st/id/811207909

Edited June 4, 2009 by juniinc

[Dharn55]

When I had the intermix and before I dropped the engine I first tested the oil cooler under pressure. Also, on the advice of Jake Raby I tested it hot as he said that sometimes the leaks don't show up unless the cooler, which is made of aluminum, is up to temperature, which can open up a crack. I put it in an oven and heated it to over 250 degrees. Still did not find any leaks. I think these leaks are fairly rare, i have only heard of a few, but they have happened. It certainly make sense to test it first.

also, when the engine is running the oil is under higher pressure than the coolant, so the oil tends to go to the coolant. but when the engine is hot and turned off the oil is no longer unde pressure, but the coolant still is so it can go to the oil.

[mylamb]

When I had the intermix and before I dropped the engine I first tested the oil cooler under pressure. Also, on the advice of Jake Raby I tested it hot as he said that sometimes the leaks don't show up unless the cooler, which is made of aluminum, is up to temperature, which can open up a crack. I put it in an oven and heated it to over 250 degrees. Still did not find any leaks. I think these leaks are fairly rare, i have only heard of a few, but they have happened. It certainly make sense to test it first.

also, when the engine is running the oil is under higher pressure than the coolant, so the oil tends to go to the coolant. but when the engine is hot and turned off the oil is no longer unde pressure, but the coolant still is so it can go to the oil.

Just got back from the dealership. Another pressure test revealed no external leaks, and they checked the oil cooler & came up with nothing - said it's fine. The service manager & the tech said that since they already pulled the plugs and found no issues, the only thing left is to wait for more symptoms or to start a tear down. All I can come up with right now is to try another shop & see what they come up with when they run a pressure test. I'm going through about 1/2 gallon coolant per week on roughly 100 city miles. None is leaking & very rarely do I get white smoke (3 times in 2 months.) So far, no power loss that I can tell. And wouldn't you know, they offered to have me look at some 987's! HAHA - not in the market just yet... but maybe I should be???

The service manager agreed with me that he thinks it might be a cracked head or block, or possibly head gasket. They originally told me that the head gasket was fine, then today said that they can't really determine anything without a bigger tear down. I'll post once I try the indy shop...

Thanks for all of your suggestions.

[mylamb]

Soooooo... I received the milkshake of death in my coolant reservoir... looks like a new flavor from Ben & Jerry's...

Last Tuesday, driving along & the coolant light starts blinking, but when I pull over, the level seems fine. Of course it was too hot to really check it out, so I waited about 2 hours and saw the milkshake in a near empty reservoir. I topped it off with the 50/50 mixture and drove home.

Wednesday, after only driving about 2 miles, the temp gauge started to rise - not past 200 but close to it. The fans were all blowing but oddly enough the coolant light was not flashing. I tried to turn on the heater but it didn't really help. About 1 block before my destination, I hear a hissing, then as soon as I turn the corner "BOOM". The idle was still fine and the engine was still running, but when I backed into the spot I could see that the car dumped all of it's coolant in the street. So the BOOM was a coolant breach, not a blown motor as I initially thought. It started fine the next day. I had it towed to the dealership & will post when I hear what they have to say. I'm hoping that this breach will be noticeable. When I had them perform a leak down test in April for the the disappearing coolant, they couldn't come up with anything.

Wish me luck!