Cloud9...68

When I bought my car in 2006, it didn't have any of the underbody pans that fit directly behind the front apron (aka "bat wing") on the underside of the car directly beneath the engine, so I'm wondering how common this is. Could you please respond with the number of underbody pans your 968 has? I'd do a poll, but I don't see how to do that on this site. Thanks.

pontifex4

Mine had zero, but I installed three. It really helped with the cooling on track.

calguy

Mine had the "bat wing" in the front when I first got it and that was it. I then bought the plastic one that attaches to that one and the metal one that goes directly under the oil pan, which attaches to the body and the plastic "middle" one.

I did notice the cooling was better afterwards although can't say it was because of that entirely since I also flushed the cooling sys. and cleaned the outside of the radiator just before installing them. One things for sure, I don't get any more oil leaks on the garage floor! ;-)

Best,

Calguy
'80 924 Coupe N/A
'92 968 Cabriolet

Cloud9...68

Interesting - so you really noticed a difference, huh? Mine ran very cool when I first got it, but it's been running a lot hotter over these past five years, despite massive amounts of troubleshooting. I'm sure having the pans would help some; trying to get a feel for how much.

968gene

Cloud, Aren't you tracking the car more these days than in the past? Also, could there be a timing issue after the rebuild? I'd vote for putting back al of the pans that the car had originally. What model year is your car?

tamathumper

While the pans are helpful, there has still been plenty of anecdotal evidence over the years that "something" happens, and cars that were always running at 8:00 suddenly started running at 9:00, and those that ran at 9:00 suddenly started running at 10:00, even with the pans in place all along and no other obvious changes or losses of cooling system functionality... So, I think there's still something going on with these cars beyond the common fan relay, thermo switch, and water pump issues.

pmason

I have a set setting on the self, but keep thinking I would put them on the car to make the underside smoother. Note mine is a race car.

dougs968

I have the batwing and the aluminum pan. That's it. The batwing was attached when I got the car and the metal pan was removed and back by the spare tire.

Rob in Oz

Mine had the back two when I bought it, but I've now bought the front ("Batwing") one (for $550 - ouch!), so now my undertrays are complete...

Rob

Paul Waterloo

I have the metal cover adjacent to the oil pan cooling fins, and there is a plastic one forward of it, both can be slightly seen in this picture:



However, it appears there was probably a cover that goes from the underside of the front bumper that spans back to the start of the plastic cover shown in the picture above? I didn't take a picture of it the other day....but is there one that is supposed to go there?

My car runs at 8 o'clock all the time, AC running or not...but it hasn't been more than 85 F when I have driven it.

Cloud9...68

Well, my plan was to start tracking it extensively, but I'm worried that it will overheat on the track. My car is bahaving exactly as Tamathumper describes in his post - when I first bought it in 2006, the gauge NEVER got above 8 oclock, then two years later, after a belt job and water pump replacement, it took a step function up, followed by another step function up a couple of months later. The second step function change was cured by a new thermostat and cap, but it has never run as cool as when I bought it. Suspecting the new (it was actually a cheapie $120 remanufactured one) water pump, I removed it to check the tightness of the impeller, but found it to be fine. I even put it in a pot of boiling water to make sure it wasn't coming loose at temperature, but it was still tight, so I ruled out the water pump. I've since completely rebuilt the engine (but didn't do a whole lot to increase its power, not that there is a whole lot that can be done to these engines anyway), and it's now running about like it did after the belt job/pump replacement, so I'm questioning my conclusion that the water pump was fine.

If this were strictly a street car, its cooling behavior would be livable, but it goes quickly to the 10 oclock mark after a series of full throttle sprints to the redline (it comes back down to about 8:30 crusing at highway speed), so I don't think it would survive a track session, particularly in the summer, of any significant duration. The problem is rpm/throttle position related - it does OK at speed. All the hoses are new, I've had the radiator flow tested (it's like new), it isn't losing a molecule of coolant, the A/F ratio meter indicates a very consistent 14.7:1 under steady state conditions, and I'm as sure as I can be that the cam timing is as correct, at least as correct as the WSM method can get it.

I plan to make sure both fans speeds are bing activated at the correct temperatures, I'll do another blink test to make sure all the sensors are working, I'll bleed the system again, check to make sure I put all the ductwork back correctly, and check the actual temperature of the hoses with an infrared sensor. If this all checks out, I may go ahead and bite the bullet for a new water pump.

Cloud9...68

Thanks for this picture of the pans - my car never had them, so I had no idea what they look like.

jpk

Check your thermostat against a known good thermometer in a pot of water on the stovetop. I had two seemingly identical thermostats, both new, same brand, same 92deg. marking, one would open 10 degrees sooner than the other. The one that opened 10 degrees cooler would have the gauge sit at 8 o'clock, and in the winter, I wouldn't get any heat. I put the other one in, and the gauge sits at or slightly below 9 o'clock, and almost never any higher.
I have the larger plastic undertray only, my car never had the metal one.
I've never had temp problems on the track during a 20-30 minute DE session. You will be moving at speed, so there will be good airflow through the rad. My cooling fans typically won't come on (or at least I don't notice them) until I'm coming back into the pits.
If you do find the temps creeping up on the gauge, I'd look at replacing the rad, or at least getting it flushed professionally by a rad shop. It's had coolant in it for almost 20 years now, so there will be some mineral deposits.

Cloud9...68

Thanks for the reply, but I've been fighting this car's cooling system for many years now, and have covered all of the items you mentioned. I did have a bad thermostat awhile back, and as a result, the fat lower radiator return hose was practically cool to the touch. With the thermostat I have now, it's extremely hot, so I'm confident that it's fully opening.

I took the radiator out to have it flushed and flow tested recently, and the shop commented that it flows like a brand new radiator. Based on the records the PO provided when I bought the car in 2006, it seems to have been very well taken care of, and the cooling system worked flawlessly for the first two years I owned it. But since I put the remanufactured pump in in 2008, it's been struggling to keep cool, and REALLY struggles under the load of full throttle acceleration.

The track where I'm going to be doing most of my driving for awhile is very tight and highly technical, so I will be doing a lot of full throttle acceleration out of corners, but there isn't any opportunity for a lot of speed during which I would be getting good air flow, so I'm afraid it would overheat during a 20-minute session here in Central Texas in the summer.

Question - If none of the tests I'm planning to perform point to a root cause, would there be any downside in re-wiring the thermo switch to force the high speed setting to come on at the point where the low speed setting normally does? In other words, completely replace the low speed function with the high speed? I would put it back during the winter, but I wonder if this would allow me to drive the car on the track, which is my primary purpose for this car. Thanks.

Paul Waterloo

If you say that this happened after putting a new water pump in, would you suspect that there could be a low flow issue or a recirculation that is happening?

I don't like throwing parts at cars....but does it still have the same water pump that you installed when it started having issues? If so, have you considered changing it?