Hot, Hot, Hot!

[TopsailBeach]

I'm looking at a 1983 944na for my high school senior for his graduation present. It's sorted fairly well, with a few problems. As a 911 owner (please forgive me) I don't know squat about the cooling system in these things. Here are the symptoms:

1. Quickly heats up to top mark (less than 10 minutes drive time).
2. Top and bottom hoses are hot.
3. Fluid in resevoir.
4. Slow removal of cap immediately after shutoff indicates pressure in system.
5. THE RADIATOR IS COLD!!
6. Fan comes on when the A/C is on...not otherwise, even though car is running hot.

My uninformed diagnosis is the radiator is clogged. I'm sure some of the wisdom of this board can help. The boy has the skill to fix about anything (give him a manual on brain surgery and he'll get the job done, as long as he can slow someone down long enough to work on....) so this will be a project, if the cooling problem isn't terminal.

Thanks for any help that you can give!

[Scott R]

Could just be the thermostat not letting enough by, but your first guess is very possible both of my 944's have had to have new radiators, they seem to clog up easily.

[TheCooler]

Thermostat

[Brando]

Quickly heating up to the max mark indicates that there may be a cooling issue. Check the thermostat (ask if it has a 120 thermostat).

If both hoses (in and out) are hot, then you might possibly be looking at getting your radiator cleaned out (or a new one, but they're not cheap).

There is going to be plenty of fluid in the reservoir. Just make sure it's between the "Min" and "Max" arrows/markings. Pressure in the system is "normal" if there's a cooling issue. that usually goes away once you have the fluid circulating throughout the engine properly.

The fans are supposed to come on when you turn on the AC. This is to provide extra cooling on the radiator while the engine drives the A/C Pump. When the engine temp hits a certain amount i think that's when the second fan kicks in all the time.

[ldl]

Well I am thinking it's the thermistat also...

But i've been having a similar problem.
After 7-10 min. of driving, the temp. shows above the last line,
and close to the solid yellow box at the right end.

I have replaced the radiator within a couple hundred miles, and I also replaced the thermostat at the same time.

After shutting down the car after a drive, the fans turn on. Or rather, A fan turns on. Looking from the front of the car, the left fan isn't turning on. And I remember both fans turning on before replacing the radiator.. So i'm gonna check out the connectors that the fans connect to soon.

Wait... Now to think about it.. I think I installed an American thermostat. Crap! That's probably why.

And good luck man.. I hope you have some luck with yours.

Bye.

[MrPants]

if the car is that hot both fans should be coming on. one fan should stay on after the car is shut off.
were these symptoms described to you? if not, what were the circumstances? (ie just sitting in the driveway with the car running, or driving?) it could heat up that quickly if it was just standing still just due to faulty fans. however, it sounds like there may some radiator problems if it was heating up that quickly while driving. the fans are not working properly for sure.
make sure everything else electrical is working properly. as im sure you know, "small" repairs snowball and add up fast.
and as a final warning: id try not to drive the car too much if you get it. youll probably end up wishing you could trade in the 911

[TopsailBeach]

I took the car for a test drive around the owner's neighborhood. When I got back to his home, it was hot (he stated from the outset that he believes it needs a new water pump), and the fans weren't on, nor did they come on after I shut the engine down. Could the thermostat be bad and both the upper and lower hoses be hot, while the radiator is cold?

[ds475]

how can i test my thermostat to see if maybe i should get a new one? i typically stay around 1/2 way on the ole tempo-meter... but it seems like maybe i could get a new one, and run a little cooler. is this so?

[justin]

ds475, you can get a lower temp. thermostatic switch, this will turn your fans on a little earlier,I have one in mine and it turns them on at the 3/4 mark instead of almost red mark.

[ds475]

i'm not talking about the thermoswitch... i'm asking about the thermostat

[MrPants]

if the radiator is cold then the radiator isnt working/clogged/etc either. could be any of the stuff everyone mentioned, or the waterpump as you thought. i dont think a bad thermostat would cause it to overheat that quickly but thats just an educated guess.
other stuff to look out for is: clutch, any clanking or chattering (14 hour replacement), and timing belts as this is an interference engine. dont mean to be redundent of you know that stuff but better safe than sorry

[Paul Glasson]

As MrPants was saying, both fans should come on if it gets hot. Only one fan is coming on when aircon turned on. Sounds like the temperature switch or other fan is knackered.Test that fan by running a wire direct from battery or bridging temperature switch.Mabe just a fuse gone.

[ronin]

waterpump

[ldl]

Same problem.

New waterpump.
New Thermostat.
New Radiator.
And both fans run while the car is hot.

Drive it for 10 min, and it is at the high end between the last line and
solid block.

[JRMock]

I'm with Ronin...waterpump.

You can take the radiator out, have in flushed, repaired, tested...etc. On an '83 it probably needs it anyway.

While it's out, take the front cover off, and turn the engine by hand. (maybe a 23mm socket and long handle ratchet on the crank shaft bolt).

While turning, watch the smooth drive wheel on the water pump, to determine if it is rotating, or if the belt is just sliding over it. (water pump drive is upper left, below the distributer, mine was frozen)

While you're there, you can pull the thermostat out of the water pump housing, and test it in a pan of boiling water. (you'll need a large retainer ring tool, and a few handy cuss words for this part... it's slippery)

The temperature sensing switch for the fans is located on the radiator, just under the water intake hole...you'll disconnect these wires when you remove the radiator. Since the sensor is on the radiator, and the radiator is cold...the fan never gets the message to 'turn on'.

Good luck...read the shop manual, and take good notes/pictures, if you replace the water pump. This will require removing the belts, and you DON'T want to fudge this up.

[rob83944]

It could be air trapped in the system also. Bleed the air out of the system. I had a problem and when I replaced my coolant the air that was trapped in the heater core caused a whole bunch of cooling issues. Bleeding the air out of the system takes about 10 minutes. Keep a watch on the temp gauge to ensure you don't overheat a blow the head gasket.

My 2cents.

[mike944]

I think it might just need a good bleeding as well. Do you know the procedure? If you need it, either I or someone else here can get it to you. My second guess would be sticking thermostat, third would be clogged radiator, and last would be bad water pump. I know most of these replies have said water pump, but here's why i think it's not. When a water pump "goes bad" usually it starts leaking coolant. it usually does NOT stop pumping water, unless there's a mechanical failure of either the impeller or shaft, neither of which i have ever heard of happening. It is possible that the bearings are partially siezed, which would prevent the timing belt from turning the water pump. If this is the case, it would be EXTREMELY bad. due to friction, the timing belt would wear right through in no time, causing many bent valves. If the car has been running hot for some time now, i would guess it's not siezed waterpump bearings, because the belt would have worn through and snapped already.

If the air in the system is not bled out properly, the pump can "suck air", causing cavitation, and non-pumping of coolant. A stuck thermostat would prevent suficcient coolant from getting from the engine into the radiator. Unfortunately, the thermostat is very dificult to remove with the radiator installed, you need to purchase a special short snap ring removal tool, or take a pair of snap ring pliers and bend them almost 90deg to clear the radiator.

Good luck,
Mike

[TopsailBeach]

Many thanks for the help. I'm inclined to offer the guy $1,000 and see apoplexy first hand. Worst case is I've pi**ed awy some $$, and best case is I have a pretty good project for the boy.

[SoCal Driver]

The heating issue is fixable. Could just be a loose timing belt not driving the water pump efficently. A cloged radiator. A bad or improperly installed thermostat. Could even be the wire to the temp sender for the gauge and the system is really working ok.

[Frank B]

Waterpump..., when were the belts replaced, or the waterpump.. should be replaced simultaniously.