You may need a new rad. Mine was crumbling though not leaking. Even though I kept it out of the red area (turned heating on in summer), it still was bad for the engine.

Also, AlanC's note regarding plugged water channels was true for me also. The reason I know is because the excessive engine heat probably caused my oil seals to deteriorate faster. Ie. After I fixed my cooling problem, I had to fix my oil leak problems.

So, get that cooling system fixed soon, else you'll also have a major job replacing seals.

If the radiator has been operating just barely good enough to keep the engine cool enough while it's running, then when you shut down, the heat contained in the block but not being removed causes the coolant to get considerably hotter.

That's the hissing sound.

Couple things to check: (1) When the temp gauge gets into the hot area, turn on the cabin heater full hot. If the temp gauge drops a bit, the radiator is marginal. If it has metal end tanks it can probably repaired by a good radioator shop. They'll want to keep it 2 -3 days. It's quite a process.

(2) Make sure the coolant level is between Min and Max, as marked on the coolant recovery tank. Have the hood up for the first start of the day. Pull the cap off the coolant recovery tank, and watch the opening while you start the engine. Rev it just a little. If you see coolant flowing up and out of the recovery tank, you have a minor breach in the head gasket. It allows compression pressures into the cooling system. The leak is reduced as the engine heats up, and running may not be different at all, but for the running hot.

Hope this helps,

Good Luck,

Bob

:>)

Hi
This is a long shot if all else fails.

Mine is an 80 also. About a year ago, my water pump started leaking, and I didn't have time to fix it myself, so had it replaced. Since then, it ran hotter - nearly ¼" higher on the gauge. I assumed that the pump wasn't as good as the old one or something. I recently took the head off (burnt valves), and found bits of the water pump gasket in the water circulation passages in the head. I pieced about ¼ a gasket in bits! The radiator was not real good, so I replaced it, but I suspect there were probably bits of gasket in it too. I guess a high pressure reverse flush may possibly get rid of the bits, but maybe not?

Alan Clarke
Nambour on Queensland's Sunshine Coast, Australia

Check or better still replace your thermostat... I would not assume the gauge is faulty specially since you hear a hissing sound.
--
ReySC.. '86 744 GLE (Daily Driver),94 944T 87 244 DL . http://groups.msn.com/Reysc/myvolvophotoalbum.msnw?Page=1

Hello,

Sounds like a thermostat to me. It's inside the little aluminum housing that the top rad hose plugs into. While you're at it do a coolant flush and change as well. The expansion tank is hissing because the cap on it is releasing excess pressure from the system because the thermostat is not allowing coolant to pass through to the radiator.

Happy Bricking!!!

Richard

87 245 DL 351,000 km
82 242 GLT 121,000 km

http://members.cardomain.com/richink

Maybe you have a faulty temp. sensor mounted on your engine. Hmm? The cap on my coolant tank also makes the hissing sound once and awhile after a long trip, but the car never overheats. Michael
--
Michael 'Street'... one AZ '85 244DL 185K miles