Car over heating

[Paulsingh]

Hey guys.

Still trying my car back on the road.

Passenger radiator was damaged, I've replaced it now and topped on coolant. Let the car run to correct temp but it carried on heating up. I was hoping it was an air lock but can't seem to get anymore out. Is there another bleed valve by the rads etc? Both rads are cold at 90deg?

Appreciate ur help on this!

Paul

[JFP in PA]

First, you need to be very careful about this; hot spots and over heating can be death to these engines. These cars should be filled with coolant using a vacuum system that eliminates any chances of air entrapment in the system. The system sells for about $100 (US), and fits any car. As the radiators are for the most part lower than the engine, replacing parts up front has trapped air in the system. The best way to get it out is using vacuum pulled on the fill opening in the rear boot. Most independent Porsche shops, and for that matter most well equipped shops, have vacuum fill equipment that can do the trick for you.



There is also a bleeder valve in the rear boot (it is the only one on the system) that can get out relatively small amounts of air, but using it takes time and is not always completely successful in getting all the air out. There are several write ups on how to use this valve.



Makes some phone calls and find out who has the vacuum system; with it you will be air free in about 5 min.

[thstone]

Go to the Pelican Parts site, find the Tech Articles section, and follow the instructions for bleeding the coolant system under Coolant Replacement.

http://www.pelicanparts.com/techarticles/Boxster_Tech/29-WATER-Flush/29-WATER-Flush.htm

Or better yet, buy Wayne's book, "101 Projects for Your Boxster" and you'll have 90% of the answers for almost any job right at your fingertips.

[jmatta]

I replaced my coolant a year and a half ago when I installed the LN low temp t-stat. Admittedly, I didn't drain the front radiators; only opened up the system underneath, but proceeded with the manual bleeding system with great success. Drove the car around for two days with the valve open and added coolant in the AM, until it was no longer required. Regrettably, I should have also replaced the water pump at the same time, after reading all the possible failures with an older pump (mine is original, 9 years, 19k miles).

I see another coolant change coming in spring when I do the pump, which I question...can I save and reuse my present 1.5 year old coolant?

As the original poster questioned, hot spots can be deadly to these engines so heed JFP's advice.

[JFP in PA]

Saving and reusing the coolant is totally dependant upon your ability to capture it cleanly and return it to the system with no entrained contaminants. In most DIY situations, not enough time or effort is made to assure that happens, so a fresh refill is in order. If you do make the effort, you will be fine.

[jmatta]

Thanks, JFP...I would anticipate capturing the coolant in a new, clean container since I purchased the good stuff from Pelican. I'd order some back up, anyway, just to be safe.

[JFP in PA]

Check prices with Sunset Porsche, they have been cheapest of late.

People seem to totally forget that the coolant is "lifetime" only if it is not contaminated in any way. So they catch it in an drain pan used for oil changes, then leave it sitting under the engine while they work on it, getting all sorts of crap into the coolant. I see cars all the time where the oil looks better than the coolant because of this. You use distilled water to prevent contamination, treat the used coolant with respect and it can happily be reused.

[Idaho Red Rocket 3]

Hi JFP,

Please tell us more about the "low temp" thermostadt. I am considering changing both of my Boxster to it, but really am not sure about the 160 degrees. I would think something closer to 175-180 dead on would be better. Both of my cars seam to be running in a range between 190-195 showing on the guages.

Where does the 160 degrees thermostat actually put the operating temp showing on the guage and more importantly, in the engine ?

[clickman]

http://www.lnengineering.com/lowtemperaturethermostat.html

[JFP in PA]

The 160 stat is an often debated item, which is most unfortunate as it is a very strong positive for the M96/97 engine. Most people think that the opening temp of a thermostat, 160F in the case of the LN unit, is the temp the engine actually will run at; it is not the case; the thermostat sets the minimum operating temperature the engine will see, depending upon the ambient air temperatures. The OEM stat begins to open at 186F, but is not fully open to well over 200, often 205F; resulting in “steady state” operating temps in excess of 210F in these cars. Before everyone chimes in that “But my dash gauge only says 180-185F”, you need to know that the dash temp gauge in most Porsches are woefully inaccurate and non linear in its movement, so don’t “bet the ranch” on what it is telling you. In addition, the design of the engine component castings also leads to localized “hot spots” considerably hotter than the average coolant temps, which is also not a good thing.

With the 160F stat, a typical Boxster (assuming not other major issues) will run at a steady state (cruising down the road on a warm day) at around the high 170’s to mid 180’s, which is just fine. Some time back, Charles Navarro of LN did before and after dyno runs on a car that was changed over to the 160 stat; results showed a very slight, but measurable HP increase, most likely due to improved thermal efficiency as the result of the lower coolant temps. In addition, because your oil is cooled by your coolant, lower coolant temps means lower oil temps, which increase the life expectancy of both your oil and your engine. With the 160 stat in place, if you get stuck in traffic, the car will still heat up until the fans kick in, but then will cool back down to its lower average temp once air flow over the radiators returns. Because the car starts from a lower base temp, it will also take longer for the engine to heat the coolant to the point the fans will run, which is quite normal. In very cold weather, you will still have plenty of heat, so that is not an issue either.

I’ve had the 160 stat in my personal cars for a long time, and I have a lot of customers running it as well. To date, I have seen absolutely no downsides to using it.

[JFP in PA]

An additional thought for anyone with a base Boxster considering going to the 160F stat; as you will be draining the cooling system anyway, this is an excellent time to swap out the base oil cooler for the “S” version, which is more than twice the size of the base unit and will help your oil temps as well. For $200, it is one of the neatest upgrades you can do on a base car.

[Paulsingh]

Thanks for your help guys. Very informative. I've managed to bleed the system and get the coolant to the front radiators. Can anyone tell me what temperature the car should heat up to until the fans come on.

I've gone up to almost 100d with no fans.

I'm sure this is a little high.