Coolant loss in '99 996

[glenndeweirdt]

I have a '99 996 that uses about a pint of coolant per month!!! I drive the car about 1200 miles per month mostly highway. I have had an independent Bosch service center check it and test oil for coolant-none shown. I took it to the dealer who checked oil for coolant-negative. They replaced the coolant resevoir (to the tune of $800) and that worked for about four months. Now it is happening again. Car runs great otherwise and it is no big deal to add a little more coolant once a month. Am I asking for trouble if I ignore this?

[BURN-BROS]

Glenn,
The water could be going into the combustion chamber. There have been reports of a hydrolock condition that breaks the top piston ring. This breakage gets above the cylinder "sleeve", then forces said "sleeve” towards the crank resulting in catastrophic engine failure. Typically you can detect combustion gasses in the coolant at most radiator shops. Hope this is not your condition...

Another scenario could be your system likes to be low due to higher pressures in the coolant system. Does the system loose all of its coolant in the reservoir over a long period of time or always a pint low? Possible fix is higher pressure cap if it applies to a 996. To verify, get the car up to operating temps and look for coolant to dump out. A steady stream of air bubbles in the reservoir, if in fact you can see the reservoir, would be a condition of a blown head gasket and the first condition I mentioned.

I am not up on my 996 engines so you will have to look around for yet another opinion. Good luck.

[glenndeweirdt]

Thanks Aaron,
Both the independent and dealer checked for combustion products in coolant and coolant in oil. Negative.
checked for bubbles in the resevoir when engine at operating temp at 3000rpm for a minute or so-negative. Do I live with this or take it back to the dealer?

What are the symptoms of dreaded RMS leak? I have noticed traces (2-3ml) of oil on the garage floor since the car turned 40k miles a few months ago. I have no detectable oil loss problems.

[BURN-BROS]

Glenn, I do not know enough about them to tell you with absolution. My gut says not to worry about very small RMS leaks. I do believe that if the leak was a significant one I would want to do something about it. I would monitor it.

The coolant going in the combustion should not be ruled out as it might be weeping in during the periods of sitting or temp transition. The test for gasses is not always definitive. Certain conditions may have to be met before the leak is apparent( this part I know from experience). Maybe a scope though the spark plug hole to verify? Coolant does not just disappear, if it isnt on the ground it is going somewhere.

[jkarolyi]

I would do a leakdown test and watch for bubbles in the coolant when it is being performed. The mechanic will pressurize each cylinder one at a time through the spark plug hole. This will tell you if any cylinders are experiencing compression loss and helps diagnose where the loss is going, whether it be through the cooling passages or oil crankcase (bad cylinder rings).

[jvmcnair]

While you guys live with mysteries, my situation seems definitive. First, a half mile from home, the coolant light started blinking. In the garage I checked the oil level using the dash device : it showed over-full. Nuts! I went in to pet my dog and attempt denial. Back iwith the 2000 996, I added 2-3 qts to fill the coolant tank -never this low before. I jacked it up and just cracked the oil plug... coolant dripped out, not Mobil-1. jvm

[FPB111]

Check to make sure that your cap is the latest update. If you have a 00 or 01 cap change it. I think they are on 04+

[FPB111]

jvmcnair,
Sorry to hear that. If you are lucky it will be the seals between the oil cooler and waterjacket or the AOS.

You may have a cracked head.

[jvmcnair]

OK, thanks for quick help. I do not understand, though. The cap? I have foamy oil on the dipstick (I did not say that, did I?) and I have coolant in the oil pan. Oh, and the engine idle is off and uneven; maybe missing. What about the tank cap? jvm

[jvmcnair]

The oil cooler and AOS? That gives me a bit of hope. AOS is a Porsche acronym I don't know. Brief explanation? jvm

[FPB111]

Water cooled Air Oil Separator
It lives at rear (towards front) of driver side of the engine. It can be changed while in the car if you have patience.

RMS or IMS QUESTIONS? READ THIS FIRST BEFORE YOU POST! SEARCH BEFORE YOU POST - Rennlist Discussion Forums

AOS, Intermix, both?-FIXED - Rennlist Discussion Forums
My DIY IMS Bearing Upgrade and AOS Replacement - Rennlist Discussion Forums

[jvmcnair]

OH!! Air Oil Separator! Something relatively new to us old guys -my '71 911S does not have one, huh? A buddy with a BMW has trouble with his AOS (the one in his car).... I will read those links, too. Thanks again. I will be back tomorrow. jvm

[FPB111]

Originally Posted by jvmcnair

OK, thanks for quick help. I do not understand, though. The cap? I have foamy oil on the dipstick (I did not say that, did I?) and I have coolant in the oil pan. Oh, and the engine idle is off and uneven; maybe missing. What about the tank cap? jvm

We have a thread hijack here the OP, glenndeweirdt, has a disappearing coolant problem. The caps have been updated a few time because of that problem.

Start a new thread about your intermix situation.

[glenndeweirdt]

No big deal.
My 996 died with a cracked block. I could not justify a $17K crate engine or the risk of a $7000 boneyard engine for a car worth $20K at the time. I sold my pristine 911SC not long after and bought a Boxster. Now looking for a Boxster S.

[jvmcnair]

My son just bot a very nice '03 Boxter S, replete with new sticky tires for $12000! I'm so proud of him. I should also be thankful to the friend who sold it to him.... jvm