BC

If the car had an issue with oil and water mixing PRIOR, then the motor could possibly not have been flushed out very well, and that snot could be in alot of places.

mark kibort

looks like old owners used tap water and it sat for a long time, as was said. green fluid is bad, change to a mixture of orange and distilled.

the part that bothers me is the drain plugs not flowing coolant. that hole goes right to the cylinder area. try and stick a screw driver in the hole and see if something is clogging it up. the passages in the head and certainly the block are pretty big (the only "passages" on the block are the two 1" openings to the water pump and the openings to the thermostat.) stop leaks, usually dont clog things (at least bars stop leak doesnt) they only react with air as it seeps out of a hole under hot pressure. otherwise, the worst they can usually do is stain the metal a tint of orange.

back to flushing. you need to pry the thermostat open and re-install it for a good flush. otherwise, it wont open and you wouldnt be flushing anything . water just would be circulating around the block and no where else. I did this by putting a toy motor gear on the t-stat shaft, so that it cant close all the way. (basically simulating the thing being hot) this way, you can flush the system and also see if you are getting flow.

If your pump was not working, you would overheat in a matter of 5 mins.
one easy check for this, is to pry open the t-stat and re-install as i have suggested above. run the car. if it overheats then, you got a water pump issue or a big clog. (sometimes the radiator can be clogged too, and that is tought to determine, because it still flows, heat builds up and it feels hot , top to bottom)
when the radiator is cool on the bottom and hot near the top, usually it means the t-stat is not opening, or the pump is bad.

one way that i checked a friends 928 for cooling flow issues, was to peg the t-stat and connect hoses to the lower radiator hose area. (meaning un hook the lower radiator from the engine. put a hose on it and point it over the fender.put another hose (usually a spare lower radiator hose) on the engine mount area and use this to feed the water pump with a garden hose. start the car and turn on the hose. at idle you should have a slow stream of water. rev the engine and you will need to turn up the hose to keep up with the water flow demand of the pump. its a good test.

mk

Bill Ball

And if there is a lot of either gorilla snot or corrosion coating those passages, it acts as an insulator. This could be a tough one to clean out.

928ntslow

Wow...thoughts and suggestions all over the map. Just what I had figured really.

I will get back out there today to do some more investigating and report back.

Bill Ball

This mantra about the coolant color is misleading. There are many green coolants, even older ones, that were and are perfectly compatible with aluminum. That's what Porsche used from the factory and I found in my dealer serviced S4 when I bought it, and that's what I continue to use with zero problems in all this time. There was a lot of promotion here of orange Dex-cool type as the ONLY coolant to use at one time, and I believe the strongest proponent of that here changed his opinion a few years ago. Today, almost all name brand glycol coolants have the correct chemistry for aluminum regardless of color.

dr bob

Keith--

+1 on what Mark says about probably having tap water in the system for some time.


There have been other reports from users who also found that they couldn't get coolant to flow from the block drains. In one case (may have been Dan locally here?) the remedy was using a piece of coathanger or welding rod to poke and prod the garbage in the block through those holes, until the debris was loose enough to get some flow.

The only iron contact in the system is the impellor, and yours looks like a lot of metal has migrated. It's not too surprising that the rust has settled in the bottoms of the block galleys.

Pumping efficiency is very much a function of clearance around the pump impellor and the space between the 'fins' on the impellor and the block where it mounts. With that much corrosion in the picture of your impellor, I'll speculate that the clearance has enlarged quite a bit. You can go through the trouble of measuring that clearance with clay, then speculating that it is or is not correct. Or just get a known-good rebuilt pump and know that it will work. A pump with too much clearance there will recirculate internally as it spins, and may only actually flow enough coolant when the engine is rev'd a bit. At that point the amount of fluid internally recirculating in the pump cavity is small enough compared to total pump flow that some might actually flow through the block and the radiator/heater/reservoir/etc. This symptom sounds a lot like what you describe early in this thread.


Back to the galley drains--

The block is cast with open areas (galleys) around the cylinders. Many other engine brands circulate water though the galleys through ports from the water pump low in that galley area. Not so the 928, where the ports sit well above the bottom of galleys, and hence the block drains that Chevy and Ford somehow manage to neglect. With multiple metals and materials in contact with coolant, it's almost inevitable that there will be scale and metal debris from the sacrificial materials used. Aluminum tends to shield itself from the corrosive effects of low-pH coolant mixes (like old ethylene glycol) up to a limit, while the cast steel impellor on the pump is sacrificial from day 1 of exposure to an acidic coolant. As the iron flakes off the impellor, it goes to that relatively dead area at the base of the cylinders and settles there. At the same time, calcium precipitates from the water used in the coolant mix ubless the proper buffers are used. The chemical additives in the coolant are pretty interesting. They gather on the calcium and functionally bind up the 'legs' of the molecules so they won't stick together. The little round molecules can then flow through the system without gathering into a salt rock formation, but rather will find low-flow areas and possibly settle there. FWIW, they tend not to gather on the iron scraps, but rather stick to the aluminum where there's a temperature change happening. Radiators and heater cores might be good examples, along with the cooler areas at the bottoms of the galleys away from the combustion areas and before the coolant gathers more heat from the top of the cylinders and the heads. Bottom line is that there may be soft calcium deposits interfering with the flow of iron crud out the drains, but they won't be bonded together as one lump. On a slight tangent, this points to the need for using distilled water in the coolant mix. While the coolant may have additives that can help tie up the calcium salts from tap water, it can do nothing to prevent those salts from precipitating in the system. Those salts still flow around the system and gather in low places.

928ntslow

Bob, great last paragraph! I have to applaud that one You know way too much about the elements of the planet than most of the owners of these cars could ever comprehend...me included! Thanks for owning a 928! lol BTW, everytime I see your avatar, I think it is a pic of a car with a parking boot.

In reference to what Bill said (and I forgot to address it) I had changed out the radiator as one of the possibilities of over heating in December. I put the green stuff in and it clearly stated it was safe for aluminum. I really don't know of any coolants out there not that aren't safe for aluminum.

Anyway, that was new coolant and was not the cause of this issue. It's what was in (or not in) before.

Dennis Wilson

Keith,

I believe all of the major brands are now aluminum safe but I did find a house brand at AutoZone that did not specify that it was safe.

BTW on the flushing always flush in the reverse direction of the normal flow. This should remove any blockage that isn't permanent.

Dennis

928ntslow

So this would mean flushing from the drain bolts is back flushing....right?

OK, so I got the passenger side of the block clear. Well, AFAIK since it is between the WP and the drain plug. I used a coat hanger and some compressed air. I made a fitting that screwed into the drain plug that has a hose hooked to it then hooked to my compressor gun. I dumped some water down the passage and gave several bursts of air to stir the crud or what ever it was up. That side drains.

The driver side, well, its clogged pretty good. I could not accomplish the same thing as the passenger side. I tried the compressed air and it is just backing up into the gun and escaping through the seams. What ever is blocking this doesn't want to loosen up.

How about DRAINO!?!? Seriously, I even tried running a coat hanger down the passage from the WP, but can only get so far. I think there are too many curves.

Any ideas?

Also, I am not sure if this is going to solve the issue. Doesn't the water flow through the passenger side of the engine, out the back past the heater valve and into the driver side of the engine back to the pump?

Dennis Wilson

Keith,

As an example, the reverse would be to run water into the thermostat housing (sans thermostat) as that is normally the outlet. The same on the heater core. Initially I would leave the block drain plugs off until the water ran clear, then install and finish flushing until the clear water comes out of the inlet side of the block. Flush the radiator the same way. After finishing the flush, remove the drain plugs and add filtered water. Check the operation of the heater, pump etc. If still plugged, a chemical flush may be required.

Dennis

BC

Maybe some of the general obstruction is in the heater core (Thats an oh-**** if you ever did that job before)

heinrich

A very well-used local mechanic uses plain dish liquid to flush radiators and blocks.

Dennis Wilson

That is actually a good product since it isn't acid like many of the flush products. I would stay away from the automatic dishwashing liquids as they are highly acid. Not sure what is in Dawn Foaming liquid but it can eat up wax and clean coats.

Dennis

marton

What he said, there is no relationship between colour and the chemical nature of the anti-freeze. Anti-freeze manufacturers just throw in whatever dye is convenient or cheap or available.
There is no standard for antifreeze that mentions a colour.

Marton

dr bob

Um, no. Not a good idea. Even with the smiley face. Draino is caustic soda in a can. Notice how the Draino can is always rusty by the second time you need some? 'Nuff said.


It appears that the pump draws from the back of the water manifold until that passage through the thermostat closes, then from the bottom of the radiator as the thermostat lets water flow from the water manifold to the top of the radiator. From the pump, coolant is circulated in parallel through the two banks of cylinders. Up through the heads then, and back to the water manifold and the thermostat.

The tap for the heater is just that, a tap. Some of the coolant is drawn off on the right side of the engine, and routed through the heater core and back to the coolant reservoir, from which it circulates back to the suction side of the water pump. The "heater core water" only gets the heat shared by the cylinders on the right side (pass side on US cars...), with not much at all contributed by the contact with the rear of the head. Keeps the heater core coolant temp a little more reasonable. The plastic reservoir gets that coolant that's shed some of its heat in the heater core, plus small pee-stream flows slipstreamed from the water bridge and the top of the radiator itself. In big terms, the heater core flow is a pretty tiny fraction of the total system flow.