Semi-overheating?
 

Needle is always on the 8. Always.

I'm driving the 60 mile commute home with the top down and enjoying myself. I got stuck on an exit ramp to another expressway and decided the car is not as much fun when it's standing still, so I decide to stay on the expressway. Here comes some fun. Merging into 60-70mph traffic from a standstill. The P-car normally has no issues with this. I get on it and somewhere after the first shift into second, I hear a thump. Not enough for me to back down, but enough for me to notice. When I settle down, I notice my needle is on the zero. See above. It's never on the zero, so I start to freak out a little bit. Traffic is flowing fine and the needle stays there. Traffic backs up and the needle stays there. 40 miles later, I arrive home and the needle is still there. I check the coolant after it cools down, and it is low. About 1/2 gallon low.

Next weekend I buy some distilled water (I have no idea what coolant is in there and I'm making plans to flush it in the next couple weeks). I fill up the reservoir and idle the car until it hits operating temperature. Then I run the A/C. Coolant level does not move. I decide to take a spin and put some fuel in it and the needle sits on zero. Coolant level is unchanged and no matter how hard I beat on it, it stays on zero.

Anyone have any ideas so I don't have to drive a car with a measly sunroof all summer?

The cap is the wrong (old) type and it is on order as of 5 minutes from now. Could that be the source of my problem?

Check to ensure that both fans are operating correctly.

Of course check the simple things, e.g. pressure test cap, fans, leaks in coolant tank, etc....but the thump is of concern and you may want to consider the possibility of a water pump failure. If that is the case, running it may not be a good idea. I assume you already checked for water in the oil and oil in the water...

Sometimes I like to run on the interstate in 4th gear and a while back I noticed mine creeping up to the 0. Recently I took of the front bumper cover and cleaned between my condensers and radiators, and got a ton of junk out of there, cigarette butts, and mostly a lot of leaves and straw. Since then it has been staying right on the 8. We are getting back to hot weather so it may go back up from time to time, but I do not recall a single instance of going to the 0 since I did this cleaning.

The thump, I don't have any definitive feedback on that. Maybe a wheel weight coming loose, or maybe you spun a rock up when you were crossing back into the main driving line of the highway?

Both fans are working at hi and lo. Changed the cap. Still hits the zero and stays there. I checked for oil in the coolant, but not coolant in the oil. I'll run a crackle test tomorrow. I'm planning on flushing the coolant next payday, so I guess that's as good a time as any to replace, what I believe, is the original water pump (92k).

It just strikes me as odd that that it only gets to the zero. But I guess that could be a water pump thing.

When it gets to the end of the '0' is when the fans turn on, ~210F-~212F according to my obd2 temp readout.

Your water pump may be in the process of failing, and can still circulate water, just not as effectively as a new pump. The fans are most likely able to pick up the WPs slack, which is why the temp gauge would get up to 0, but not go any higher.

Check underneath and look to see if you have any seepage around the water pump.

your thump might have been transmission or motor mounts moving.

m

I'm hoping it was the motor mount. That's on the schedule to be replaced in the next few weeks. The water pump / thermostat is going to set me back a couple weeks though. I have a go live date of June 20th due to finances. My project list for the next few weeks is:

Pull front bumper and clean radiators - Done
Relocate frunk cable - Maybe today
Replace broken brake wear sensors. Probably today
Tie rods - This weekend
Flush coolant
Water pump / thermostat
Center engine mount
Oil change

the engine likes to steady-state at 180. folks with low temp (160) tstats note that their cars still run at 180, even with the tstat open sooner and more often. so, something has thrown your engine off. the coolant loss is disturbing but perhaps was low before and just not noticed? similarly the bang might just be coincidence. as all have noted, a visual inspection is the best step - underbody panels, serpentine belt, coolant hoses, water pump, tstat housing, idler pulleys, a/c and alternator pulley, radiators (noting that the a/c condensers are in front and block full view).

Beg to differ; folks with the 160 stats coolant is actually running cooler (usually around 170-174F steady state) while the inaccurate and non linear dash display continues to indicate around 180 or so. Cars with the OEM stat also show nearly the same dash indication, but are actually running at more like 210F. The dash gauge is little more than an idiot light that moves, and any indication that is even remotely correct is pure coincidence..........

i'll buy that. so presume then that engine wants to steady-state at around 174 and low temp tstat lives in the open position.

oem tstat at 180 cycles on and off, resulting in temp peaks and overall higher average operating temp (theory being that Porsche used a 180 tstat to increase start-up temps for emissions; competition cars not required to meet emission standards run 160 tstats as standard).

in the context of this thread, what would cause the engine to lock-in at a higher temp. initial assumption is that the gauge is too inaccurate to be trusted. what if the tstat stuck closed? would the engine find a higher steady state temp (engine bay fan cooling, etc.)?

First place I would look would be how clean are the radiators, we often find literally pounds of crap (leafs, grass, paper, even a dead bird or two) between the AC units and the radiators on these cars.

http://www.gjlenterprise.com/radiator/4.jpg http://www.autoscope.co/wp-content/u...6/DSC00369.jpg

Check your coolant tank, pull the rear trunk carpets and see if you have a leak. What color is your tank? If yellow its old and may have a pinhole leak. Check your water pump and thermostat. Maybe the thermostat is not working well. Finally clean the radiators. The 9x6 cooling systems all suck.

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Cleaned out the radiators last week. they weren't too bad.

http://i896.photobucket.com/albums/a...49024113_n.jpg

The coolant level might have been low before hand. It's not something I check normally as I've never had the temp drift past the 8 before. With 92k on the pump and thermostat, I figure it's probably best to replace them both anyway. I'll post pics of them when I tackle this one. Probably June 7th-ish.

ETA: The coolant tank is original and still white. I don't notice any moisture when I lift up the carpet in that area.

Toady.....
If the water pump has run for 92k miles, there's a good chance that the impeller blades are worn or even broken. In he real world this can point to poor pumping action so less coolant is pumped around the system......maybe it's just general wear and tear causing the slight overheating, so replacing the pump & t'stat as you mention may be the way to go.

What revision cap are you using?

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I had a similar experience the other day...but it was really hot here in CLT and I was in serious city traffic. Mine went to the '0', but no higher. Both fans kicked in and it seemed to stabilize. I have only had my car since January, so I have no idea if this was normal. Took it to P dealer here for an oil change yesterday and asked service consultant about it - he said it was perfectly normal.

I know JFP is adamant about these gauges being woefully inaccurate, but it seems the end of the '0' is when the fans should kick in...but I am a newbie to watercooled P cars.... I miss my VDO gauges :(

I have owned my boxster for a year and the temp needle hung just past the middle of the 8 in 180. Just recently it has started to creep up between the 8 and the 0. I monitored the temp with an OBDII gauge and it seems to actually be running in 192-205 range and 212 sitting still when the fans kick on. Is this a normal temp range or is it running a tad warm?? Just changed to new cap with same results.

Just to add another data point. 2000 base. Fans operate correctly on Lo and Hi. I sit in LA traffic alot and so know my temp gauge like my watch. Lo fans turn on when needle is just before the right side of the '0', turn off when it drops to about 1/4 from the left side of the zero. The reported temp at turn on via either the OBD data or the climate control hack is 104-105 C. This is perfectly normal behavior by all accounts. I have actually never had the fans kick up to Hi when driving, even in summer traffic and my temps run in the low 90s when cruising at speed and not pushing the car particularly hard.

I no longer worry about this. I leave it to you newbies....

Mine, 2000S, is EXACTLY the same! Thanks Teleski for the confirmation. I guess my local dealer is pretty spot on. After all, I was going to pay to have the problem diagnosed and he talked me out of spending money...and then gave me a discount on my oil change...:)