Try the...

Hey guys. I got the idle speed issue fixed, but I'm having trouble bleeding my coolant. I'm following the procedure on Pedro's Garage, which is pretty much the same as in the Bentley manual. Here's what happened:

• Top off coolant. Run car and ensure it's topped.
• Warm it up at 2500rpm for 10 minutes.
• Check coolant. It's still full.
• 2500rpm for 5 minutes + 5000rpm revs.
• Check coolant again. Still full, but coolant all over from overflow.
• 2500rpm for 5 min again with revs.
• Let it cool at idle.
• Check coolant. Still full and more coolant overflow.
• Test drove car about 2 miles. By the time I got back home I got the low-coolant warning light.

I let the car cool, then topped it off again. It lost about a gallon of coolant in the process. This was all before my idle speed problem. So once I fixed that, I did the procedure again. Same result. Since then, I tried bleeding it two more times using a "quick bleed" procedure I found on the 986forum. The first time was about an hour and a half after the second attempt at bleeding, so the car was still warm. The last time was this morning. The car was cold, so it never really got hot using that process. On both of the last two attempts, I left the bleed valve open in between and while driving. Same results. While the car is hot, the tank is full and it's blowing overflow like crazy. When it cools off, the tank is mostly empty.

I'm wasting a ton of really expensive Porsche coolant, and making a mess in the street (I hope nobody walks their dogs in the street for a while). I don't want to try bleeding it again, as that will just waste coolant.

Is it likely that the thermostat is not opening, and that's the problem? I can't think of anything else that might cause behavior like this. BTW, when I did the first attempt at bleeding, the temp got up pretty high. I'd guess it was 2/3 of the way from 180F to the next mark, which would put it somewhere around 200-205F. I didn't note the temp on subsequent attempts except the last (which was below 180). While driving it, it gets up to about 190, and just stays there. It is only 22F outside here though. All fans seemed to be running too.

It's not your thermostat - if your thermostat stayed closed, the car would overheat dramatically and the level in the tank wouldn't change at all.

Is the car leaking coolant except for the overflow?

You have a mid-series 986, right?

If it is not overheating (190 isn't that hot and could be explained by having debris blocking the radiators), and not leaking coolant when sitting in the garage (e.g., if it is only overflow) and the car is not overheating like it did before your bleed, my first easy guess is that you have a bad overflow tank cap (or you have the beginning of a crack in your coolant overflow tank). The cap on the overflow has a built in pressure valve to blow coolant if the car overheats (so the car doesn't blow it out through a hose, which is bad). These caps go bad every few years, and will allow the coolant to expand (since the system is no longer pressurized) and the tanks fills up and overflows - I have seen this happen a number of times. Try buying a new coolant cap and see if that helps.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

My car is a '99, so it's an early one.

The cap I've got is 996.106.447.03. I just called Sunset Porsche, and that's what they are showing is the most recent. I replaced it last year. However, when I go to Pelican Parts, they are showing .04 as Genuine Porsche. Seems odd that they'd be different.

As far as I can tell, the car is not leaking from anywhere but the overflow. It is all coming out just inside of the right, rear wheel (all over the suspension and the diagonal brace). There are no other spots of coolant on the garage floor. I just looked under the pad in the trunk. There is a very small amount of coolant down there. However, there are also several white lines on the side of the tank showing that coolant was leaking down the outside of the tank from the top. It looks like it was possibly coming from along the side of the oil filler tube, and down the driver's side of the tank. The tank looks nice. It's not yellowed at all, and doesn't have that opaque look that those tanks get when they are really brittle. I see no evidence of leaks, other than up top. That little section at the top where the oil and coolant filler caps, then dipstick and the bleeder valve are had a LOT of coolant in it from me trying to open the cap while the coolant was hot.

The level in my tank is NOT changing at all. It does change when it heats up, and then it blows it out. I assume that is due to overflow. While the car is warm, the tank is always full. Of course, it's dumping coolant constantly too. So then, when it cools off, it is low.

BTW, following the Bentley procedure for bleeding, there are a few places where they tell you to open the cap (carefully). When I do that, there is always a TON of pressure. It takes me around 10 minutes to open it. I turn it a tiny bit until I hear hissing or bubbling of the boiling coolant, then I let it sit until it stops. Then I turn it a tiny bit more, and repeat.

I'm not sure if I read this wrong, but the car never did overheat before.

I did not replace the thermostat (yet). I did swap the coolant pump from my original engine to the replacement engine.

to see if they were hot. However, the heater did work. Is the heater downstream of the thermostat or no?

open but to be sure check the hoses to/from the radiators that they are hot, carrying hot coolant.

Did you replace the t-stat? If so, did you test it before installing it to be sure it opens at the right temp? Did you install it correctly? (Not sure if it can be installed the wrong way.)

I think Red_Lightnin! has a good idea regarding the coolant tank cap. Unless the cap is new (has a part number ending in something higher than 00 or 01 (I think 03 or 04 is the latest revision of this cap) you should replace the cap. It will leak, if it is not already.

Sincerely,

MarcW.

but I did have the heater on while attempting to bleed. It may have gotten hotter than 212F, but I'm pretty sure it didn't hit the mark above 180 (which would be 215F). Then again, I know it got hot when I drove it the first time, but I can't remember how hot. Certainly nowhere near the top of the scale, but it MAY have gone above 215F. I don't think so, but I can't remember for sure.

the hottest heat setting manually to I believe open a valve to let coolant flow into the heater. In cars equipped with climate control the coolant flow is unrestricted, the amount of heat put out is controlled by the air flap that directs air through the heater and how much cooled air it mixed with this hot air.

Also if the car is equipped with a Tiptronice the pneumatically triggered coolant shutoff valve must be opened for the bleeding process. The electric switchover valve must be switched off for this purpose. If you do not have a PST2 removing the Tip control module fuse B1 WITH THE IGNITION SWITCHED OFF is the factory manual alternative.

(Also, the instructions say to remove both caps (oil and coolant) then remove the tank cover and open (lift the bow) of the bleeder valve located on the tank). Replace the oil cap. Fill the system with coolant and run the engine at idle and top off with coolant until no more coolant flows into the cooling system. The coolant level should be at the lower edge of the filler neck. The coolant temp must not exceed 80C or 176F. Close the reservior and warm up the engine by running it at 2500 rpm until the T-stat opens (after approx. 10 minutes) when the coolant temp reaches 90C (194F). Check the radiator supply lines and return lines in the front wheel housings they must be hot. Allow the engine to run an additional 5 minutes at 2500 rpms and every 30 second *briefly* reve the engine up to 5K rpms. Rpm surges are important for proper bleeding. The level warning light can come on during this process. It can be reset by shutting off the engine then restarting the engine. If the coolant level goes below the min mark of the tank stop the process and using extreme caution allow overpressure to bleed off and top off with coolant. Again intermittently rev the engine for 5 minutes. Allow the engine to run at idle until any activated radiator fans switch off. Then turn off the engine. With extreme caution remove the coolant cap and top up coolant until the level reaches the lower edge of the filler neck (when the coolant goes cold again the coolant level should be the max line). Close the bleeder valve. Reactivate the Tip ATF shut off valve. )

If the A/C compressor is off the fans come on (low speed) when the coolant temp (measured IIRC at or close to the water pump exit is 212F. (If the coolant temp rises to 216F the fans switch to high speed.) The fans shut off when the coolant temp drops to 205F.

You can't really depend upon the temp gage for anything other than the coolant is cold, warm, or possibly hot. The gage is not that accurate. I have developed some sense of how my car's coolant gage reads by monitoring the actual coolant temp in real time using an Obd2 code reader/data viewer and monitoring coolant temp and noting the needle's position on the dial. At best I can get within (maybe) 10F degs but the dial is really more a glorified idiot light than a true temperature gage.

As the above paragraph in parenthesis shows, running/racing the engine to get the coolant hot to remove over time air pockets in these cars is very difficult and this I believe makes the purchase of a proper vacuum pump that pulls a vacuum in the cooling system to remove air and when used properly ensure an air pocket free refill of the cooling system a worthwhile tool to have.

Sincerely,

MarcW.

My car is a manual trans. I don't know if I have climate control or not. I have the standard panel that all of the '99s had (according to the owner's manual). That's good info anyway.

I definitely did not check the radiator hoses in the wheel wells to ensure they were hot. Your instructions are more detailed than any I've seen before. I appreciate that.

For the 5000rpm revs, I just rev it and let it come right back down (maybe 2 seconds total time). You think that is enough, or should it be slower?

I ordered a UView 550000 Airlift Cooling System Leak Checker and Airlock Purge Tool Kit from Amazon tonight. I'm not going to go through this again. Besides, I have to change the water pump on my wife's truck, and it will be nice for that.

I may try to bleed it again tomorrow using these instructions. I will if I don't get called in to work.

Can you pressure test the system to see if you have a leak. I had a small leak at the base of the pressure relief valve; its very easy to over tighten the screws and pull the threads. It does not take much of a leak to cause the system to boil . pressure test and listen you should hear the leak. Never throw out old coolant tanks you never know when you will need relief valve parts. I just did my tank and the old one looked brand new

That is excellent advice from Alcantera, and Marc is right about opening the heater core.

Another point on the coolant cap - just because it is the most current design does not mean it is not bad. I have replaced this item at least three times - my hypothesis is that once the system overheats and blows through the cap, the pressure valve never works quite the same. Just conjecture.

This being said, if the cap is less than a year old, it might still be good. On the other hand, if it has vented several times now, you will probably need to a new cap anyway (they're pretty cheap). But you should definitely pressure test the system and if you choose to bleed again, make sure you have the heater core open.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger



Edited 1 time(s). Last edit at 02/23/2011 11:25AM by Red_Lightnin!. (view changes)

Started the bleed procedure again. I just did the first part to warm up the car. I discovered that my thermostat is working (radiator lines in the wheel wells were hot). I was still getting fluid dumping so I shut the car off. I could hear the coolant boiling. I did see vapor coming from the area of the filler cap and the bleed valve. I suppose it could be from the bleed valve, but I think I'm going to change the cap anyway. I don't see any evidence of a leak anywhere on or around the tank (except the vapor up top). I'm hoping that's the problem.

I called my local dealer, and they've got the .04 cap. My wife's gonna pick it up at lunch, so I'll let you know how it goes when she gets home.



Edited 1 time(s). Last edit at 02/23/2011 02:26PM by Yippee38. (view changes)

If it doesn't, you might also want to check the lines to the front radiators as well - you can access them through the wheel wells or from the under the car. I just realized that if the thermostat is working, and the lines to the engine are warm and you can't find a leak otherwise, and your cap is new, the only other idea that comes to mind is someone jacked the car improperly and crimped one of the lines to the front, which would explain improper cooling with with a new cap and no obvious leaks.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger



Edited 1 time(s). Last edit at 02/23/2011 03:04PM by Red_Lightnin!. (view changes)

If its not the cap then look here; first remove the screws and look for signs of leaking around the base. These screws go into the plastic on the bottle if you overtightened them the screw holes look like little lumps . Take a counter sink and take only the bumps off , replace the "O" ring and then tighten very lightly . Only about as tight as you can turn a screw driver with your finger tips. I would go rent a pressure tester and pressurize the system . If you have no leak down your golden [tinypic.com]

All of you guys were right. It was the coolant cap. Replaced it with a new one, and the problem disappeared.

Of course, while bleeding I discovered two other problems. One is that the engine threw two codes while doing the first 2500rpm w/revs bit. Both are AIR pump related. P0410 and P1411.

The second is when I went to flip down the bleeder on the cooling system, it just flopped over. The bleeder is sticking way up high. It's like it's lodged open. I don't think that will be a problem, so I think I'll just drive it like that. If it becomes a problem, I can always replace it when the weather is nicer.

On the positive (besides the coolant problem being solved)....Right when I went to take it for a test drive is started to rain. I needed gas badly, and while I was at the gas station, it turned to freezing rain. I stopped at the auto parts store and picked up an extra quart of oil, and when I came out, it was big, puffy snow flakes. The drive home (my first trouble-free drive since replacing the engine) was a BLAST! I did a 180 in one intersection rather than turning left. There was a car coming or I would have just kept going around. I drifted through a round-about. I did a donut in the intersection at one end of my street. And then I did two at the other end of my street. There were two kids walking near the last intersection and they gave me an ovation. WHAT A BLAST!

Glad the cap solved it.

As for the air pump codes, if the car is running fine I would just clear them and see if they come back. The air pump is just for emissions, so if the car runs fine and passes emissions don't worry about it.

As for the bleeder, I am not sure what you mean - do you mean the bleeder valve is stuck open or the little metal handle on the bleeder valve?

As for spinning around, while I love the skidpad I prefer it when it isn't spontaneous - I put the Continental DWS tyres on my car and they work like a charm.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

So we'll see.

Yeah, the bleeder valve is stuck all the way open. You know how when you flip it up there is resistance due to the end of the metal handle pushing against those little raised areas on the plastic? Mine is open so far that the metal doesn't even touch the plastic, by about 1/8".

Those were not spontaneous donuts. They were planned, and they were damn fun. I've got winter tires on the car, and I've never had a problem with traction before. In the past, if I try to get the rear end to come out, it would, but then it would snap right back. Last night, the conditions were really slippery though (perfect). Freezing rain that turned to snow mean we had ice covered by a layer of snow. THAT is slippery. I still can't help but smile when I think about it.

Since this last post, every time I drove the car and it got warm I would smell coolant. I figured it was the vapor escaping past the bleed valve, and didn't worry about it. A few days ago while driving the low coolant light came on again. I pulled over and checked the coolant level while the car was still hot. The coolant was showing at the bottom of the fill lines (the "minimum line). I drove the car home and parked it to let it cool. After it cooled, I checked the coolant level again and found that it was showing full. . Ok. While doing this, I removed the cap so I could shine light into the tank to get a better view of the fluid level. When I put the cap back on, it was very tight screwing on. I'm thinking I cross-threaded it. I drove the car and within 3 miles I got the low coolant light and the car was getting very hot (215). I got it home and parked it. When it cooled, the coolant tank was almost empty; it took about .75 gallons to fill. When I removed the cap, it did look crooked like I had cross-threaded it. When I put the cap back on, I made sure it spun on easily and tightened it up (remember, this is a new cap). I drove the car again, and had got high temps and low coolant light again. Now I know I screwed up by cross-threading the cap. What I don't understand is what caused the initial low indication.

I've heard people say that they leave the bleed valve open all the time and it doesn't cause a problem. However, I'm wondering if because my bleed valve was "stuck" open if it wasn't behaving like a very small leak in the system. I'm thinking that at this point my best option is to replace the whole tank to ensure it has not leaks, and that way I'll get a new bleeder assembly at the same time. I'm going to have to drain the system, but I've got the Airlift tool for draining and vacuum filling the system. I'm going to put the LN thermostat in at the same time.

Is there anything else I should check? BTW, when it was hot and blowing fluid, I looked underneath for other leaks, but saw none. I know, based on that, that the front rads are good, but I wonder about the heater core. If it was leaking, would it drip on to the undertray and the ground?

... coolant bleeding instructions found here:
[www.pedrosgarage.com]
Scroll down about half way for the instructions .
You may have left a bubble of trapped air inside.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

1) We covered the coolant cap
2) If the heater core is leaking, it should end up on the ground
3) When you say high temps, how high?
4) Have you pulled up the matting in the rear trunk to check if the tank is leaking?
5) It is possible your bleed valve is allowing coolant to escape - if so, the area around the tank should be very wet
6) Low fluid when hot is very unusual - I am almost wondering if part of your problem is air in the cooling system, which would explain the level fluctuations and the high operating temps - I seem to remember that the car needs to be on a 10% (or something like that) angle in order to bleed properly and that the heating system needs to be on
7) Do you know if your front radiator fans are working? When the car is stationary and the needle is in the "0" of the 180 the front fans should be running - if not, the front fans are not working properly and may not be cooling the car properly. Not a problem at speed, but if the fans aren't working you will overheat very quickly in traffic or while sitting.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

prevent coolant boiling which can lead to localized overheating which is not a good thing.

Also, this allows vapor to escape which can over time lower the coolant level.

Close the bleed valve.

Make sure the cap is on properly.

Get the cooling system nice and hot so that when stationary the radiator fans come on. Let them come on once then shut off then come on again. You may help this along by raising the engine speed to 2K or so. As soon as the fans come again shut off the engine.

Let it sit while you check all around the car for any anti-freeze odor or fluid leaks. If you want 'tent' the fluid access bay with foil. Check the underside of the foil for any condensation. If any present there's a leak in the coolant tank area: tank, cap, or bleed valve may not be sealing properly from being left in an open position.

Sincerely,

MarcW.

I ordered a new coolant reservoir from Sunset parts and another new cap. Sunset ROCKS BTW! Great price! I'm going to do a complete drain and refill with the Airlift to ensure I don't have any bubbles. I can't close the bleed valve. I pushed on it pretty hard, but was afraid if I pushed any harder it could crack the tank. I should have the part on Thursday or Friday. I'll let you know if that takes care of it.

and when you refill it use Porsche anti-freeze mixed with distilled water.

Good luck on your coolant reservior change. Porsche tech told me the job's "fiddly". (He's from the UK and still uses the UK lingo.)


Sincerely,

MarcW.

Fiddly is not the word I would have chosen. It took about 4 hours for me, and most of that was reconnecting the hoses. I can't see the logic in the way the Dr. plumbed these lines.