andreic

Hello,

I first need to introduce myself. My name is Andrei, and I've had a 1975 Porsche 914 for several years, on which I did all the work myself. A few weeks ago I decided to bite the bullet and also get a 1997 Boxster 2.5L to see if I like it better than the 914. (There is not enough space in the garage for 2 cars...)

The car appears to have been well maintained by the previous owners. It has 114k miles. Despite this it has caused me quite a bit of trouble in the 3 weeks I've owned it so far. After only 120 miles the adjustable pushrod that actuates the left-right movement of the shifter failed (the bushing appears to have worn out and cracked), leaving me with only gears 3 and 4. I've managed to fix that myself.

Unfortunately a few days ago a member of my family was not careful and hit the left side of the bumper against a brick wall, breaking a few small pieces of the bumper, and also cracking the left radiator (ouch!). I picked up a replacement radiator from a local junkyard, along with the supporting bracket (the old one was bent), and installed them. After that I followed the procedure outlined on Pelican Parts for refilling the coolant system and eliminating air bubbles.

Despite doing things as described, I noticed during my first drive after the incident that the temperature gauge went higher than before. If I assume that the marking on the gauge in the panel between 180 and 250 degrees is at 215 degrees, then I seemed to be operating around 205 degrees (needle straight through the middle of the "0" of the 180). Before replacing the radiator the needle barely ever went above 180. Also, when I stopped halfway through my 10 mile test trip I noticed a small amount of what appeared to be coolant dripping from the inside of the wheel liner, making a puddle about 2in wide. The coolant level in the expansion tank never went down at all, and when I parked the car back at home nothing dripped from underneath it.

Questions:

a) Are the higher operating temperature a sign that I may still have an air bubble in the cooling system, and if yes, how do I get it out? I tried revving the car up, all the way to 5000 RPM, both with the car cold and with it hot, but that does not seem to make a difference. The fans do come on as they should, both at the low level and at high.

b) Should I be concerned about the coolant leak I had seen, and replace the hoses and clamps that go to the radiator (which I have not replaced), or should I just keep an eye on them for a week or two, and if things are ok not worry about it? The hoses seemed to be in great shape, as well as the clamps. (I am thinking that the dripping might have been just water accumulating in the wheel liner, since it had rained quite a bit the day before? Before putting the liner on I had tested the hoses by running the car quite a while, without a single drop leaking. Or maybe when an air bubble went through it temporarily caused a higher-pressure condition which forced some coolant out?)

Thanks,
Andrei.

mikefocke

Multiple burps to get out the air are frequently required.

Replacement radiator tested? Right anti-freeze water mix? Any radiator shop has the tools to solve your problem.

Welcome.

Macster

The replacement radiator may have a leak. Or it may have something in it. Did you try back flushing the radiator with a garden hose and makeshift adapter before installing the radiator?

There is supposed to be enough cooling margin that the engine can remain cool enough with just one radiator but I've never tested this. (I've had a radiator fan quit on both cars and as far as I could tell the engine coolant temperature and A/C performance was unaffected.)

The Boxster cooling system is hard to refill and get all the air pockets out without using a vacuum lift system.

You want to make sure as the engine runs and warms up that the hoses leading from the engine to the radiators get hot as the T-stat opens up and lets coolant flow. Then you want to make sure the hoses from both radiators get warm to as coolant flows through the radiators and returns back to the engine. The hose temps want to be about the same. Ideally you should have a nice infrared temp gun in your tool box so you can "take" the temperature of the hoses and even the radiators to see they are about the same..

For a hot pressure test you can first with the engine cold be sure the coolant level is correct. You might have to remove the cap and the screen and visually check the level. Trying to view the level through the tank is risky as the tank gains a stain that can look very much like the fluid level when in fact the level is quite a ways down. Do not overfill the tank.

Once the level is ok then make sure the tank threads where the cap screws to the tank are clean and the cap is likewise clean and free of any coolant residue.

Might mention too often a cap leaks. The older caps are pretty bad. Newer caps with a part # ending in "02" or "04" are recommended.

Install the cap and be sure you tighten it down properly. It can take more force than you might at first suspect.

Then start the engine and take the car for a drive around the area until the engine is warmed up. Back home raise RPMs to 1K or so and hold until the radiator fans come on. They should come on at 212F degs. They'll run until the coolant temperature drops to 205F degs.

Anyhow, let the fans run a moment or two then shut off the engine. The heat load in the engine will raise coolant temperature and pressure and if there is any coolant leak you are going to know it as the leak drips (or gushes) hot coolant.

Stephen Tinker

^^ What Mike & Macster said ^^

However, for a slightly shorter "burping" procedure try this - under the plastic shield just below the coolant fill cap you will see a chromed D shaped valve lever. Lift it up into its vertical position which opens up the pressure relief valve. Run with the valve in the up position for a couple of days or at least 3-4 complete heat cycles of the engine. This will get rid of any air bubbles and will drop the coolant level as the air is expelled, so be prepared to top up the coolant.
Return the D ring to the horizontal after a few heat cycles.

der Geist

I've used this technique as well. It worked perfectly for me.

Macster

There is a problem with the technique.

The anti-freeze is to lower the freezing point of the water and has no effect on its boiling point.

The nominal boiling point of the coolant is 212F.

What keeps the coolant from boiling -- flashing to steam at the hottest places -- is pressure. It is pressure that keeps -- by my direct observation -- even 226F degree coolant from flashing to steam.

With that valve open then the system is unable to build pressure. Thus this risks the system developing steam pockets where there is coolant.

In an effort to rid the system of air pockets steam pockets can form and thus the engine suffers from localized overheating.