924S-944-2.5NA running hot and slight imbalance.

SolReaver · 02-21-2010, 06:30 PM

Hey Fellow inmates.

I have set aside some quality time with the 924S to work Out a few bugs.

Currently, the engine is running "a little hot" Images of a large red flashing light from the Movie "Airplane" (a classic) come to mind. The engine warms up and is currently full of weak but good antifreeze. The Temperature Gage gets to Just at the edge of the red zone, and sometimes just a few mm into the red when driving.

I recently did a full waterpump service So I am reasonably sure that the waterpump is working well. If it is any consolation I am sure that it doesn't leak. Also the car is a little cranky, with the occasional miss, which is usual as she has been sitting a lot lately. The buzz and excessive shaking might be a balance shaft.

Any ideas on the overheat would be appreciated. I replaced the thermostat with the Water pump, so it is new. I suspect that the overheat MIGHT be due to a bad factory part. But, that is kind of rare and I was wondering if I might be overlooking something. The system has been "burped" holds pressure and seems to be working fine. I was wondering if the Temp gage is out of calibration? Again, this is a remote possibility and possibly someone who has seen this before could suggest another cause.

Thanks,

AA_Ezra · 02-21-2010, 06:48 PM

I, have had my fair share of overheating on my car, When i smaked the dash the temperature would jump lol. Flushing the system never hurts (prestone) has worked well for me. Are you're fans kicking on? I have a low temp thermostat and Fan switch but I think the first fan should kick on at the half way point and the second fan should kick on at the first line after the half way point before the RED zone. that way you can kill 2 birds with one stone A. fan switch and fans are both working B. The temp sensor is acuratelly showing the temperature because the fans turn on. Did you Also install a new thermostat ? by miss do you mean it miss fires during idle or on acceleration when you're driving?

smokin_944 · smokin_944's Garage

A couple of things SolReaver. Where thermostats are concerned, use OEM only (Wahler)not Napa or any other type. 3 temp ranges available for Thermostats. You could go to a lower temp thermostat for one. Thermal switches come in 4 temperature ranges, from cold to hot. 823.959.481 E is 65/60, 823.959.481 is 75/70, 823.959.481 D is 82/77 and 823.959.481 F is 92/87 degrees. Trouble shoot your fan operation to make sure all is good, then post your results and we can take it from there... If the temp gauge uses an early sender, cleaning the connector would help. The fitting is brass and it gets a buildup.

SolReaver · 02-22-2010, 09:14 AM

AA_Ezra: The system is WELL flushed. THREE temp ranges for thermostats? That could be it right there. Perhaps I am used to a low thermo and it is running a hotter one. Yes, I did replace the thermostat when I did the water pump. SO, The running warm condition is recent to that repair. By my best recollection, the first fan kicks in when the second does, So, I will check that connection as well. The road debris that took out my PS tensioner took out some wiring up front.

Smokin_944: Cleaning the temp sensor connector...Check. It sounds reasonable and it can't hurt. The thermostat came from Pelican in the batch of parts that came for the WP replacement. I will have to check the brand. Like I said, the first fan may not be kicking in earlier than the second so I have a few things to check.
FOUR temp ranges for fan thermos?, yea, I will want a lower range for sure, Let me check all the connections as it was running fine before the WP rebuild.

Today I go back in and check the tension and timing of the belts. I have a bit of a buzzing to the engine and I suspect that one of the timing sprockets may be mis-indexed. I was pretty careful, but to be honest I might have missed something so I will pull the B shaft sprockets and double check.

Thanks for the info guys. It gives me something to work with. Much appreciated. I will keep you posted.

SolReaver · 03:58 PM

Quick update folks: I pulled off the belt covers and checked the marks. Everything lines up fine. However, the car did have a bit of vibration so I took off the Balance belt and pulled the Bal Shaft sprockets. A careful examination of the woodruff keys in the shaft and in the sprockets seems to indicate I mis-indexed the lower balance shaft. Although the notch on the sprocket was right on, the shaft itself was 120 degrees or so off. I will put it all back together tomorrow and road test it to make sure the vibration is gone.

IS it possible that the overheat was caused by the bal shafts being out of sync with the motor? It is probably wishful thinking of me to hope that fixing one problem will fix two symptoms. But, these cars are so darned fussy and precisely engineered that I can't rule it out entirely until I fix it and road test it. I can only speculate (wildly) that the engine, might have been fighting itself and that caused some kind of friction or strain that created more heat or made the engine work harder. It is an odd possibility.

SolReaver · 02-23-2010, 11:48 AM

More info: The bal shafts are all in order and the engine does run a bit smoother. (go figure!) So, leaving the covers off I hooked up the alt and ran it up to operating temperature. It is still running a bit warm. The temp needle hangs just on the line of the red. If I turn on the fan or headlights it goes into the red, If I shut them off It goes just outside of the red. The good news is that it is steady and doesn't go into the red very far. The bad news is it started raining which means I take a break from the project.

While I am here and have it up on ramps, I was going to check and re set the Cam belt tension. Next is cleaning the temp sensor at the front of the engine next to the air horn snorkel thingie. If time and weather permitting I will swap the new thermostat for the old one it replaced and see if that does the trick.

SolReaver · 02-24-2010, 03:26 PM

Problem fixed. It was a bad in box Thermostat. I put the old one in and now she operates between the last two white lines and stays away from the red. It really stinks getting a defective part. Especially when the thermo is so hard to do on this car. (seriously folks, what is THAT all about?)

Both fans kick on at the same time, around the line to left of the center. So, I still have some minor tweaking to do. With a bit of luck another day will do it.

smokin_944 · smokin_944's Garage

Excellent work SolReaver! Now you have to set up the car so the first fan kicks off first at slow speed. You can choose when the fan starts by picking a temperature and a corresponding thermal fan switch. For example I was using the coolest of fan switches, 823.959.481 E which is a little too cool 65/60. In cool temps the car wasn't maintaining temp so I went up one range to 823.959.481 which is a 75/70 thermal switch. Perfect. Good luck with the tweaking...

drew1 · 02-25-2010, 03:19 PM

Echoing smokin - good work Sol

Running hot is a pain & hard to find problem.

Your problem kind of reminds me of years ago. Temp switch on wife's 931 was acting up & car running hot in town. Night before she & a friend were riding to Atlanta for some big teacher conference, I told her you better take Grace's car or turn on AC in town to keep fans running. Grace wanted to ride in 931 instead of her Honda but let my wife know she was cold.

dangerous · dangerous's Garage

I'd pull your radiator and have it flow tested at any radiator shop if you haven't already done so. A freshly rodded or new radiator makes a wold of difference. Getting all of the air bled out is another imporant step.