Matt O.

I might have a small cooling issue in the 968. First, let me say the ambient air temp yesterday evening was 105.

Shortly after starting, the temp needle started to creep towards the second white line. Even in the 951, it doesn't get that high. Started touching the bottom of the second white line, and the high speed setting on the fan kicked in. I was idling for a few moments while the wife was returning a redbox, and it stayed at that level and the fan stayed at the high speed.

As we started to drive away, it came down just a hair, with the fan staying at high speed the entire time.

It has been a few years since I had to do any work whatsoever on a 944 cooling system...

Please refresh my memory. The things I should look for are:

- Temp difference between upper and lower hoses.
- Whether or not the fans kick in, both low and high speed (high obviously works, not sure about low)
- Potential air in the system (although, highly unlikely, it has been two years since the coolant flush).

Any other items that I should check out? Re-read Clarks Garage. Just soliciting additional feedback.

The other side of the coin is that maybe it's just hot as all heck... but even in some of the hottest Florida summer days the 968 wouldn't creep to the second white line... so I think it's more than the fact it's triple digits.

Thanks,
Matt

Tom M'Guinn

Well, I do a visual check to make sure both fans are running and that nothing is blocking the radiator. Since the high speed fans didn't bring the temps down (if I understand you correctly), it's probably not a fan issue (assuming both fans are working). It will run hotter in 105 degrees, but it shouldn't be at the upper line even in that temp in my experience. If fans are working and radiator is unblocked, I'd do a pressure test to see if you have a leak anywhere -- coolant can be sneaky and mist out under pressure in a way you never notice. The problem is that is sucks air in when it cools to replace the lost volume -- and suddenly your car needs venting. If it holds pressure, and the fans work, then I'd check the t-stat to see if it's going south.

Matt O.

Both fans on low, initially with ac on, then as it warmed up with ac off also. Upper and lower hoses very hot to touch. Hose to head hot as well. Reservoir very hot as well. Idling shows coolant movement in reservoir, appears to be circulating.

Idling for 5 mins now, temp needle at halfway mark. High speed setting NOT ENGAGED yet.

Will drive around for a bit and see if it creeps up.

Matt

Matt O.

Didn't even drive away, temp bumped up over halfway (slightly), high speed setting kicked in. Temp is a needle width above dead center. Will drive around the block.

Matt O.

High speed fan stayed on the entire drive. While driving, needle stays about one width above dead center, at stopped needle goes to a width or so below top white line. Pictures to follow.

Matt O.

Picture of temp gauge at idle. Seems high to me, need to get an exact reading somehow of the coolant temp. Gauge is so inaccurate.



Also, voltmeter seems very low, need to dig into that when my tools get here as well.

Rich Sandor

This sometimes happens when the thermoswitch is ready to fail. Normally it kicks in the highspeed fans at a certain temperature, and prevents the coolant from getting too hot. If the thermoswitch is on its way out, it won't kick in the fans till a higher temp, and then of course it has a hard time getting the temps back down. Especially if the rad is clogged with dead bugs or bent fins.

As you know, even if you recently bled the coolant, you can still get air bubbles form in there in a sealed system after a few years. You mentioned the temp rises when you stop. Does the temp drop if you blip the throttle while stopped? If so, there is definitely air in the system.

Matt O.

Thanks Rich. It's been a while and I forgot alot of the tips/tricks/troubleshooting. I'll take her out later today and see if I can figure anything else out. I did not notice it drop on just a increase in RPM, but I'll check.

What are your thoughts on the voltmeter? I'm used to it reading dead center between 12 and 14. Not barely 12. Somethings definitely up there.

Matt O.

By the way, just trying to gather data -- receiving my house hold goods next week, tools are in that shipment. Thanks.

porsche_968

Try this...get up to temp, turn thermostat to high heat, Let coolant circulate with high fan to see if the gauge needle drops.
Turn off car and jack up the driver side, open bleed screw on top of engine and add some water wetter or water.
drop car and restart and recheck, See if that helps.....luck

judge

Just a thought [with no mechanical background] but the combination of temperature and charging seem to me to point to a waterpump/alternator drive belt issue

JohnKoaWood

Water pump is driven by the timing belt.

Alternator is driven by accessory drive belt.

OP,

Heat soak is killing the alternator / battery / cables with a quickness.. You WILL need new cables, you may need a new alternator / regulator / brushes and possibly a new battery.. verify the voltage at the battery with a multimeter to rule out a gauge issue.

High temperature is likely caused by the age of the coolant / components of the system.

Verify the sender for the gauge (multimeter).
Verify the function of the thermoswitch (LOW speed should be on with AC, and at 92degC, and high speed at 102degC, verify the temps using an IR thermometer, these temps are dictated by the equipped thermo switch, there are 2 of them available, 944 online has them listed as 75 and 85 degrees.. factory manuals show 92 and 102...YMMV)..

Pressure bleed the system, and check for leaks at the same time using a pressure bleeder.

although your description makes it sound like these bits are working properly.. these are the free checks.

Next would be to flush and service the cooling system.. if temps are still creeping, you can have your radiator fully flushed / ultrasonic cleaning (hot tank some people refer to it as) at a specialty radiator / machine shop.. this would remove MOST of the contaminants from the radiator, and MAY restore proper function to it.. if it is gunked up or clogged a new radiator is in order.

Lastly would be to have the water pump changed, I would make sure this is done during the next timing belt change.

New water pump, new radiator, new coolant, functioning sensors, all should be right.. IMHO there is something amiss with either your coolant mix, water pump or radiator.. in that order..

SpeedBump

My bet is the cables being replaced would fix it, I had the same symptoms as OP. First thing you need to check is are you actually running hot.

I replaced my cables with some from Robby on here and everything stabilized.

JohnKoaWood

There are other options available...

Just not mainstream yet...

SpeedBump

I was in throw parts mode at it when I was trying to get this under control and the cables I did to fix the voltage issue were what finally got the temp gauge right. I did not follow my own advice to see if it was actually running hot for long while and so I now have a nice 4 year old cooling system and lots of 4 year old sensors installed.