Not a stuck open thermostat.

[adallak]

9 hours ago, Logan said:

I would take a close look at the water pump impeller. Some pumps are actually using plastic ones. The pump could also be a counterfeit Gates.  

https://www.impalassforum.com/threads/water-pump-impeller.341985/

Logan,

I can actually take off the top plate of the pump to see if the impeller is spinning free, right? Or it will leak if I put it back (in case it is okay)?

Heck, it is probably possible to pullout the shaft with the impeller and replace it with one from the new pump? 

That would save a lot of time. 

[rockfangd]

I replaced a hub assembly a number of years ago. Drove it for a year, took it on my usual 500 mile trip, 2 blocks from home I hit a bump (I live in NY) and it broke. It was bad enough that when I took off it literally fell apart. Had I been far from home I would have been screwed. 

I do not use cheap parts. It only gets worse. Calipers, hoses, etc...

[rockfangd]

4 hours ago, adallak said:

Logan,

I can actually take off the top plate of the pump to see if the impeller is spinning free, right? Or it will leak if I put it back (in case it is okay)?

Heck, it is probably possible to pullout the shaft with the impeller and replace it with one from the new pump? 

That would save a lot of time. 

You might be able to. Pull cover off, inspect it, and if need be swap it

[adallak]

1 minute ago, rockfangd said:

I replaced a hub assembly a number of years ago. Drove it for a year, took it on my usual 500 mile trip, 2 blocks from home I hit a bump (I live in NY) and it broke. It was bad enough that when I took off it literally fell apart. Had I been far from home I would have been screwed. 

I do not use cheap parts. It only gets worse. Calipers, hoses, etc...

A hub assembly falling apart. Ouch.

[adallak]

1 minute ago, rockfangd said:

You might be able to. Pull cover off, inspect it, and if need be swap it

That's the plan. Thanks. 

[Logan]

Never worked on a LT1 pump. I think the cover comes right off and uses a o-ring. But I think the impeller is pressed on. But it may allow you to at least see if anything looks amiss.

Lot's on Google and Google Images. Corvette...z28 etc..

 

It is a reverse flow pump.....so you might have to think about what the flow is doing...

 

https://www.corvetteactioncenter.com/tech/knowledgebase/article/1992-1996-corvette-technical-article-lt1-reverse-flow-cooling-system-526.html

 

How does a lt1 water pump work?

 

 

Coolant flows from the lower radiator hose into the water pump at the thermostat through the heads on the way to the block. The reverse flow pump acts as a vacuum pump in drawing the water out of the block. It then passes the thermostat and returns it to the radiator via the upper hose.

[Logan]

Please note the info about the dual flow thermostat. 

https://www.corvetteactioncenter.com/tech/knowledgebase/article/1992-1996-corvette-technical-article-lt1-reverse-flow-cooling-system-526.html

[adallak]

Update. I have replaced the radiator. Pieces of rusted junk came out of the system. Cannot flush it, unfortunately. This time coolant looks reddish, rusty... Nothing seems to be wrong with the water pump. At least the (steel) impeller does not spin 9b the shaft. Nevertheless, I am planning to replace the pump, stat, radiator cap, and the temperature sensor.

If it was indeed the rust, it will build up sooner or later. Need to get out of friend's place. Probably will have to take to a shop for a flush if the problem persists. 

 

[BodybyFisher]

Sounds like you have narrowed down the problem. 

Do this when you get a moment, tear off the end tank (bend the tabs/flange) on the intake side and look at the cross tubes, my gut tells me they are going to be gunked up.  

I would have the engine professionally reverse flushed if you are finding rust.  Dumb question I don't know the answer to >> does the LT1 have cast iron heads?

[adallak]

Mike,

I tried to fill the system with distilled water, run a bit and then refill with 50/50 mix. Guess what - the system took only 1 gallon. I expected at least 3 gallons since there was some coolant in the engine block. The full capacity of LT1 is 4 gallons.  Looks like there is a restriction inside the engine (cast iron) block. Now I am screwed up. 

Tow truck, unknown mechanic, lots of $$$ and an unknown result. I am at friend's, but I cannot stay there forever...

[BodybyFisher]

First I have ever heard of anything like this.

[rockfangd]

How much coolant was removed this time the system was apart?

Have you tried running the engine to get the coolant to flow?

I have to think more about that engine to remember if the coolant passages could be blocked. 

[Logan]

Are you using Dexcool or traditional green coolant?

Dexcool can cause rusting in the air pockets on iron blocks. Long known problem. 

Personally I use the good old fashion green stuff in everything. 

[adallak]

Logan,

I always used only green one.

 

Took of the water pump and it was perfect, so put it back with new gaskets. The radiator is also new (not a perfect fit as I was assured, but probably will work.

Something go is wrong. Tried to fill the system with distilled water the way I always did through the expansion tank with the bleeder on the stat housing open and it only took 1.5 gallon instead do of usual 3 gallons. 

I am stuck. There must be tons of rusted debris in the block and I have no way to flush leave alone take off the stupid knock sensors, GM decided to use as drain plugs. They hollow and twist and brake on old engines. 

Anyone knowing the guts of LT1?

[adallak]

17 hours ago, rockfangd said:

How much coolant was removed this time the system was apart?

Have you tried running the engine to get the coolant to flow?

I have to think more about that engine to remember if the coolant passages could be blocked. 

Rockfungd,

It is hard to tell how much exactly was removed, but I know the system takes almost 3 gallons. I did exactly what I have always done, abd it took only 1.5 gallon. 

The water pump was clean, took it off and put it back with new gasket. The radiator us new. The stat us new. 

I am afraid there us blockage inside the block and that caused all the issues... 

I am scared to take the car to unknown place for flushing. God knows how they flush and what will happen next. 

I am at friend's, but cannot stay here forever. 

 

[rockfangd]

Ok. 

When you are running it is it purging air bubbles? I only use purging funnels for coolant now, Have for a long time. Without this it may not be as easy to monitor purging. 

You can squeeze each hose while you watch the level in the funnel and it shows a good indication of flow.

[adallak]

The car is fixed. The new radiator did it. All the temps are back to normal. Have not taken it for a long ride, but I do hope everything will be fine. 

Is it okay to keep only distilled water in the system for a few more days? I want to drain as much of rusty old coolant out of the system. 

I am still thinking of removing those stupid knock sensors/drain plugs to do a proper flush and drain. 

If I do break them (most likely I will), can I use broken sensors to fool the computer? 

[BodybyFisher]

Glad to hear it

[rockfangd]

That's good to hear. Must have just been air.

I would not drive too far with the distilled water. I would buy a bottle of flush and run it through, then flush it good. Then refill with the proper coolant mix.

I don't know that I would mess with removing the plugs and sensors. Will probably never get it all out no matter what you do. Would be more of a headache than its worth

[adallak]

Another update. 

I have ruled out the recently replaced thermostat, but IT was the problem. It gradually failed within a few months. 

Will keep the new radiator anyway. 

On the side note. I am in Pittsfield, MA now and for some reason people of this town are particularly in love with 1993-1996 Fleetwoods. People stop by and ask if it is for sale quite often. It will be for sale eventually within a year, but not right now.