I have had my 71 cutlass supreme 350 conv. for 25 yrs, I allowed a new mechanic to change the oil and flush the coolant.
Problem is he only topped of the system with a 50/50 mix after flushing the system. The car when checked this spring was only good to 20 ABOVE zero and it was COLD here south of Chicago last winter.
Freeze plugs did not pop, no water in the oil, heads were just pulled and had warped a little but the head gaskets were not blown. Crossing my fingers I put heads back on the car ran GREAT till I shut it off then it over heated. Boiled over big time. Never had a HOT light on.
Idling for 20 min with the radiator cap off, car was fine then all of a sudden gush of antifreeze 10 feet into the air out of radiator opening.

Engine does not seem to over heat while running. infrared gauge seems right
Compressions great
NO BUBBLING WITH RADIATOR CAP OFF

differential diagnosis
? cracked block
? system plugged building up steam bubble ( coolant coming out very heavy brown)

Plan: flush system extensively changed pump , changing radiator, flushing heater core, pull drain plugs on block.

ANY SUGGESTIONS after the above?
I think it is pull the engine and look for cracked cylinder.. would be next step.....(really looked with heads off no visible cracks or rust)


If case is bad how much does it hurt value to change to a "NONNUMBERS MATCHING" short block.
If I do this suggestions on engines?

How hard to convert to a larger engine?

New Paint, New interior and new chrome last winter in for a penny already

Thanks in advance for any help


Brian

 

You may have had an airpocket that caused the fluid to shoot out the radiator. Refill, start the engine, don't stand with your face over the neck but observe to see if you have flow when the thermostat opens.

As far as your coolant temp rating, you need to buy a gallon of straight antifreeze and a tester. Drain about a quart out of the radiator petcock. And add a quart of straight antifreeze back in. Drive for about 5 miles, let the radiator cool, test and repeat until you reach -34*F on your tester. You can do this over a period of a few days if you wish.

 

Thanks
New radiator , New cap, has over flow catch, new hoses, new thermostat (installed correctly) new antifreeze at minus 30plus. This was all done prior to boil over. New suggestion was reflush "the he++ out of the engine" radiator replaced a second time as well as water pump and antifreeze. Mechanic and I want to try everything prior to pulling engine.. And yes there was flow when engine was running could see in radiator opening.

Thank You for your suggestions and please let me know if you can think of something else.
Also mechanic now says that there is no vacuum. But car starts sounds great, BUT I haven't taken it on the highway where the problems start.

Thanks Brian

 

I don't understand why a 50/50 mix of glycol gave you a problem. That was the standard mix for anti-freeze back in the day and still is today.

 

Put the cap on and see what the temps go to.

 

 

It sounds a lot like the new mechanic doesn't understand these cars. Yes a coolant flush is a good idea every so often, so is having the rad cleaned and pressure tested. But there's no excuse for leaving the block full of water and having such a diluted mix especially over the winter. IF there's any head damage or machining required you likely can bill it to the shop that did the work if you identify the problem was caused by their work.

You shouldn't need a new radiator and new water pump just for a coolant flush and refill. T-stat; sure. Something just doesn't sound right about what is being done to your car. Was there a problem with it before all this work was done?

 

 

This is why concentrate still exists. If you flushed a block with full water, and just pulled the bottom hose, you are going to get 50/50 if you put in 2 gallons of pure 100% antifreeze as most of the cars hold 15-16 quarts, which is 4 gallons. Good rule has been "can I get in 2 full gallons of 100% coolant on my final fill?"

 

I buy my coolant as concentrate all the time. Main reason is it costs the same as 50/50 and I know how to dilute it for the mix I need. We typically get -40° during our winters so it's important to have something that will perform. Most people dilute with tap water. I use distilled - same as when I used to top up cells in the battery.
You make a good point. I use my hydrometer to test the coolant after a flush. I also test it annually to see if it's still in range. Such a simple test that can be done with the hydrometer or a multi-meter. (yup) I prefer the hydrometer though because it's quick and easier.

 

More Help Please, comments

So It appears that the engine was overheated. The antifreeze/coolant was good to 20 ABOVE Zero. I believe it froze and then I drove it aprox 4 miles to the shop where it was being repainted. Ran perfectly prior to and during that drive. I sat the rest of the winter in a heated shop.
This spring the shop started it and it has been a nightmare since.

The heads were removed and redone. The machine shop says the heads were warped 40 thousands. Still not running correctly wires distributor were replaced. Still not running correctly the carb was replaced, the carb which was replaced with new several yrs ago was WARPED. The base plate was so warped that it was noticeable just looking at it. Radiator and water pump were changed.

Now, it seems to be "back to nl". Our best theory is that like the other two cars "serviced by this mechanic." the collant froze Not hard enough to crack the block but hard enough not to circulate. Not having a hot warning light I drove all 3 of the cars until they really over heated. Overheated to the point of warping the heads and carb.. Also for some unknown reason oil dip stick sleeve has broken..

Questions: Engine now runs great. But have I ruined anything else?
Any Other theories? explanations?
Comments/thoughts please

Brian