Randy V

Did you burp the cooling system yet?

Mongo

I'm at work. Plenty of burping here after lunch.

The car? Not yet. I figure I'd just replace the thermostat, than do the burping and farting thereafter.

dr bob

Air in the system doesn't offer the symptoms he described. Air-locked will overheat at idle, but stays overheated even with engine RPM's up. Symptoms shared point to a bypassing thermostat.

hacker-pschorr

Has anyone suggested changing out the T-stat and both rubber seals?

If not, I think that should be high on the list.

Mrmerlin

Eric post 59.

NOTE the 928 cooling system is self bleeding.
nothing fancy is needed to remove air from the system other than filling the bottle till the level stays constant ,
then running the engine till the fans come on.

Then installing the coolant cap and with the heater turned on full hot ,
drive the car for about 5 miles then park it,
let it cool off ,
then top up as necessary.
this process will work just about every time you will try it

Mongo

Then popping off that line in the past that connects to the driver side top radiator end tank was completely useless in bleeding, yet messy to boot. Oh well.

hacker-pschorr

I was being sarcastic, it's been mentioned about 20 times in this thread.

Mongo

19 actually.

dr bob

I make it a point to remove the vent line from the radiator nipple, and fill the system until coolant appears there. More for indication than function. The system is self-purging, so long as all the little vent lines slope up towards the reservoir. Those connect to little nipples on the reservoir right at the top, and will work so long as the liquid level in the reservoir is below the nipples. The hoses in my car sort of slope up, but there are low places in them as they pass the right side distributor cap and the front of that cam cover. As soon as those low spots have liquid in them there's no path for vapor to get to the reservoir. So for me, no issues so long as I don't fill the reservoir all the way to the top. If I put too much in or the coolant expands that much on first start-up, I end up doing the creative hose-squeezing to clear vapor from the water bridge. The "vent" nipple on the water bridge isn't at the top either, leaving a small pocket that's only filled after the thermostat opens and the faster-moving coolant entrains the air and eventually burps it into the reservoir while the heater valve is open.

safulop

OK everybody, no more advice until he changes his thermostat...

Speedtoys

Mongo

Thermostat is here. Tearing into it on Saturday. Bad news though, my block drains are frozen. When I change the coolant I am going to run distilled water twice through it before adding the Zerex G05. And, don't tell me to try breaking them again either. I already stripped one back in 2013. No way, no how. I have seen the damage caused by too much force to the block

dr bob

"Frozen" block drains, as in "they've never been off before" frozen? Or "really seem to be tight because I followed the factory torque spec when I last installed them" frozen?

There are some horror stories about folks actually fracturing the bosses when the bolts have been in too long, especially in an under-maintained system. Not a good thing.

Meanwhile, bolts that have been out and back in with factory torque often need what seems like a lot of torque to get them loose. With the car up high enough for easy access, I use a 1/2"-drive 6-point socket on the drain bolts, with a long ratchet or breaker bar, and a hard 'snap' pull on the handle to get them loose.

Dave Chamberlain and I shared similar thoughts on the factory torque spec. There's a separate thread dedicated to this subject. My long-time recommendation for the plugs includes using some Teflon thread sealing paste on the bolt threads and on the faces of the sealing washers. Then us 12-15 lbs/ft of torque on the bolts and call it good. The Teflon paste lubricates the threads and hopefully reduces the galvanic corrosion that tries to make the steel bolt part of the aluminum block. It also lubricates the washer so it doesn't gall going back on or coming off.

Effectively clearing the block galleys next to the cylinders take a little more than a couple fill-and-drain cycles with distilled water. Especially in under-maintained systems, minerals in the last batch of coolant will precipitate out in the colder sections down in the block (and in the bottom of the radiator). When the coolant additives are working correctly, they wrap around the calcium, rather than allowing it to "plate out" in the heads and the radiator. It's a good idea to get that stuff out, and it usually takes either the drains or some pretty serious circulation velocity to carry them up and out through the radiator hoses. That velocity doesn't happen with a fill-and-drain, although that fill-and-drain will help reduce the amount of old coolant left in the block. In Andy's case with the car in the relatively non-freezing SF bay area, running with less than 50% coolant concentration won't be an issue. Others who don't drain the block will discover that getting two gallons of coolant into top of the system only will be a challenge.

----

At my first coolant change, I was timid about the block drain bolts and left them in. The thermostat came out, so I could put the garden hose into the block ports and push a lot of water through. Then several cycles with distilled water poured through, hoping to dilute the softened hose water still in there. Later, working on a clinic car where we pulled the bolts, we found that we needed to use a piece of hard welding rod to break up the chunks of precipitate just to get the coolant to drain. I was emboldened by the bolts coming out, and encouraged by the chunks removed, enough to go after the bolts on my car the next time it needed cooling system service. No chunks came out, and inspection with a mirror and borescope camera showed everything clean and shiny inside. Two-year coolant change intervals really pay off it seems.

Mongo

Thermostat is out. Got a mess in the valley now. Goodbye super clean engine

Mongo

My thermostat's inner seal is still alive. Hope a new TStat fixes it.