Turbo is overheating when it idles

pozican · 10-29-2006, 12:57 PM

Freeway speeds? Fine -- Through town no traffic? Fine -- Hitting every stop light? Overheat.

I have no idea why this is happening. My electric fans are on when the car is running... I'm having coolant issues (springing leak every couple of drives) but I tackle those every time they come up WHEN they come up. I do properly vent the system before I drive.

I have a cone air filter replacment to the stock one, and it is in the stock location - Could this cause an epidemic?

How do I begin to troubleshoot?

Techno Duck · Techno Duck's Garage

Are you sure both the low and high speed fans kick on? You can pull the connector on the fan switch and jump the pins to test the fan relay. Its possible only your low speed fans are turning on causing your overheating problem.

The only reason i can think your car is over heating at idle is air in your cooling system. Even though you have bled the system, i would continue to do it..these cars are a pain in the butt to bleed sometimes, i am trying to bleed mine myself.

Its also possible your thermostat is sticking, but i would think that would cause your car to overheat all the time.

Are you sure the gauge is not just giving you a false reading?

Here is how you test the fan relay..

http://www.clarks-garage.com/shop-manual/cool-01.htm#laterelaytest

Razorback1980 · Razorback1980's Garage

Techno gives some pretty good tips...especially on the fans. Make sure they work correctly. Buy a thermometer to check the temperature to make sure the gauge is reading correctly. You may find it is not.

pozican · 10-29-2006, 09:35 PM

You would be surprised at how hard that switch is to get to from the top!

I was gonna try, but I would have to drain oil and coolant (then again coolant is draining on it's own every couple of drives -.- )

So when it stops raining ( seattle soooo... summer? ) or I find time I'll put it in the garage and go in from the bottom...

Thanks,
I'll keep you updated.
-Alex

Razorback1980 · Razorback1980's Garage

Where is the coolant draining at? Does it sound like it's boiling when you stop after it overheats?

Crumpled952 · 10-30-2006, 01:55 AM

I hate to be the one to tell you but you may have a small head gasket leak. Overheating at idle and continuous leaks would indicate pressure into the cooling system. There is numerous threads on the Rennlist and Clarks garage has excellent stuff as well to help. Good Luck.

pozican · 10-30-2006, 06:03 AM

Quote:

Originally posted by Crumpled952
I hate to be the one to tell you but you may have a small head gasket leak. Overheating at idle and continuous leaks would indicate pressure into the cooling system. There is numerous threads on the Rennlist and Clarks garage has excellent stuff as well to help. Good Luck.

The first time it leaked it blew a heater control valve -- Now it almost looks like it's coming from the lower radiator hose -- Havn't found it yet, but it doesn't leak at idle...

Sounds expensive, and hard to do...

Is it?

Crumpled952 · 10-30-2006, 06:32 AM

Yup. It involves the timing belts etc so it can be done by a reasonably skilled DIY'er but requires some special tools, torque wrench etc. Because these are "interference" engines screwing up on the timing belt can, and usually does, lead to some very serious and expensive consequences. It may not be the head gasket but your symptoms match exactly the symptoms described in "Clarks garage" for a non-catastrophic head gasket failure. Best have a read of that.

Lanny

Techno Duck · Techno Duck's Garage

Do a compression test and it may or may not turn up a headgasket problem. My headgasket fire ring split in two and was leaking into the #3 cylinder, the leak was not bad enough to show up on a compression test, but did leak coolant overnight and caused the car to fire on 3 cylinders during startup.

The best thing you can do to check and verify leaks is to get a cooling system pressure tester. Pressurize the cooling system to about 10psi and let it sit for 15-20minutes. If the pressure drops, pull all 4 spark plugs and look into the cylinder for signs of coolant. Otherwise start poking around the car looking for the leaks.

bearone2 · 10-30-2006, 08:30 AM

higher rpm, torque/twisting/loading, may be hiding a leak that doesn't show up at idle.
btdt.

it doesn't sound like it's totally being bled as much water as your needing to add.

Razorback1980 · Razorback1980's Garage

I don't think it's air in the system. That's why I was asking if the coolant was bubbling after shutoff. Usually a sign of a head gasket failure. The fact that pressure is blowing things in the cooling system is telling me two things. First, you have a head gasket leak...second, your radiator cap isn't working and relieving the pressure so something else blows. Check it out before you blow the radiator...plastic on the ends are not real strong. Follow Techno's suggestion and that should provide a lot of information. Coolant smoke (white) at startup is another sign to look for.

pozican · 10-30-2006, 06:02 PM

I was thinking about this today. Why would a small leak in the head gasket make me overheat ONLY when I'm at idle?

Also I was having issues finding the non-catastrophic head gasket failure on clarks-garage -- Seems his search function needs work...

Thanks,
-Alex

Techno Duck · Techno Duck's Garage

I dont mean to come off like a jerk, but seriously, pressure test your cooling system because there is no point at us all speculating at what it could be. There are a handful of possibilities that are causing this and a proper pressure test will identify all of them.

One thing, does the car fire on 3-cylinders after you ran the car up to temp and let it sit for an hour or two? That is a tell tale sign of a headgasket problem.

Overheating only at idle leads me to believe your high speed fans are not working. Did you ever jump the fan switch connector to check the relay?

pozican · 10-30-2006, 09:40 PM

Havn't found time to jump the fans -- Will do first

I don't think it's a headgasket leak because I don't have bubbles in my overflow tank.

I'm gonna pull it into the garage probably wednesday, and have a good look, maybe I can get off of work early tomorrow since I had to stay in late today.

I'll figure it out and keep you updated -- Thanks!
-Alex

[edit]
It doesn't SOUND or FEEL like it's only firing on 3 cylinders.
Is there any sure fire way to tell?
I would assume that it'd be obvious...

Razorback1980 · Razorback1980's Garage

Here is why a blown head gasket overheats at idle. The reason the gauge reads hot is that the air being pumped into the cooling system is very hot...not sure what it runs on a Porsche engine but probably in excess of 1000 degrees. That tends to make the water get pretty warm, however at high rpms obviously much more air is pumped into the cooling system building pressure much quicker and that opens up the radiator overflow cap and the air pressure escapes. With the hot air gone, water temp goes back down. At low rpms, the opposite happens. It takes longer to build up pressure because there are less rpms so the hot exhaust gases remain in the cooling system for a longer time....therefore the water temperature goes up. Also at idle, there is not an extensive air flow going through the radiator which compounds the problem. Usually at high rpms you are traveling down the highway and the amount of air flowing through the radiator is higher. Fans move some air but come no where close to traveling down the highway at 70. Put your hand out the window at 70 then feel the air flow in front of the radiator to compare the two. Much much faster air flow at 70.

Do the pressure test if you have the equipment and also check out the compression numbers. The two will tell you a lot.

Techno Duck · Techno Duck's Garage

You would know if the car is only firing on 3-cylinders. Its going to sound like a diesel for a few seconds. If you want to know what it sounds like, pull a ignition wire and start the car. Dont do it for long though. Its just good to know what it does sound like for reference.

pozican · 06:00 PM

Fans make a weird noise (squeling ish -- intermittently) but both high and low work.

What's next?

Jumper test:

---------------------------------------------------------
|....................|..Ignition on..|...Ignition off...|
|.Low speed....|...Fans on.....|.....Fans on......|
|.High speed....|...Fans on.....|.....Fans off.....|
---------------------------------------------------------

When the car is started (for short period, fumes made me turn it off) low speed fans are OFF

When the A/C is on, high speed fans are ON.

Ideas?
Thanks,
-Poz

Techno Duck · Techno Duck's Garage

Fumes? You need to be more specific than that.

Low speed fans will only kick on after coolant in the radiator goes over 92'C. High speed will kick on at 102'C.

Just to clear things up, with the a/c on only low speed fans turn on. I thought it was high speed also until i tested it myself this past weekend.

What is the mileage on your car? If the fans are squeeling then they could be going bad. Turn them both by hand, any serious resistance?

Now that you ruled out the fan problems, pressure test the system. This will probably reveal whatever the problem is. If it turns out to be just air, use the pressure tester to help bleed the air out.

pozican · 10-31-2006, 06:32 PM

No major resistance -- With the car's front end in the air, I bleed the system, and instantly coolant ran through the bolt when I started the car -- I'm sure it's well bled -- I'm gonna do a compression test and test the radiator cap next -- Not sure where to get a pressure tester....

Techno Duck · Techno Duck's Garage

If you have an Autozone nearby you can borrow one.