Best aggressive coolant flush for Chev blitz

Can anyone recommend a good, effective flush to deal with rust in an old engine? Not after those superficial 7 minute ones but a three day or similar one.

Chasing a long term overheating problem in the 216 in my chev blitz. I fully disassembled, checked and reassembled it several years ago. It overheated before hand. The coolant passages particularly around the cylinders were packed solid with rust. I spent three days with screwdrivers, bits of wire, air, gurney etc. cleaning the passages out. It runs well, good power, great oil pressure (for a 216), good 2nd hand radiator and it still overheats. There is lack of flow I'm pretty sure - currently no thermostat, water pump impeller looks good. When I first put it back together (15 years ago) I used straight water, but drained it after every use (where it spent upwards of 5 years sitting sometimes). But in the last 4 years I've used 50:50 diesel coolant.

A week or so ago when it was say mid 20s I ran it, while idling it climbed to 90*, I drove it up a reasonable hill for a bit and it dropped to 85* and was blowing fairly warm air on me (no cab so get full rad flow on my body), got to the top and turned around, went down hill and the temp climbed to 95* - cold air blowing on me and the bottom hose is not very warm at all. I'm thinking either I didn't clean the passages properly (I can't specifically remember doing the head) or my early use of water created/encouraged old rust to form.

I know the proper fix is to pull it out and pull it apart again to clean but there is no way that's happening. I'm flat out keeping things moving in my project world with three young kids, animals, a full time job and too many other areas. If that's the only option either it's going to sit there getting crapped on by the bloody swallows for ever or the 216 is getting turfed for something else - possibly the 3cyl deutz (is that the definition of irony?) I've got sitting sitting here that needs a turbo and a home... If I could just run a good flush for it I'd feel I'm giving it a good last chance. It's already trying my patience by not building up oil pressure if it sits more than 3 months (gotta pull the dizzy and spin the pump with a drill, getting quite quick at that)

Fill it with vinegar and run it. If there's alloy parts in the cooling system, you may want to dilute the vinegar with water. Run it till the water is filthy, rinse and repeat.

You may want to put a stocking in the top hose to catch the barnacles. And check the temperature gauge is working accurately too.

So was that the good second hand radiator that had the tanks removed and professionally cleaned?
or the one that was under the sheet of tin round the back of the shed for 15 years and looked good on the outside?

The impeller looks good/ Does it actually push water out of a hose when the engine is rpm is increased?

Themostats are fitted for a reason...it worked perfectly well during the design phase I would imagine,
Its a necessary part of the cooling system to ensure it all works correctly and should be in place.

It would be great if a quick flush was the answer to an overheating problem but unfortunately it is rarely a fix.
Start at the radiator, it may not be the wanted option but it will rule out a very large part of the cooling system and will be a known quantity if further diagnosis is required.

I'm with Chocs on the thermostat. You need that. I find the rear cylinders will cook. I'm not sure why they run better with one, but I suspect the water in the block gets a big purge when it opens. It seems the water pump is just pumping around the front cylinder without one. I welcome other opinions on this.
Some engines have a small bypass hose which must be in place, or they'll cook. Hillman Hunter comes to mind (if no heater, must have the bypass hose).

A couple of suggestions, Jarrod.

The thermostat helps build pressure in a pressurised system, maybe cut out the guts of the thermostat and reinstall the plate for a bit of restriction.

The thermostat is used to hold the water in the block until the set temperature is reached.
Then It opens and allows the full flow through the radiator for cooling.

As mentioned above the thermostat regulates the flow by opening and closing. If you take the thermostat out it will allow full flow through the system passing the water through the radiator too fast for heat transfer to occur. The water must be up against the cool sink of the radiator long enough to lose heat to the cooling fins.

Against what might seem logic, too fast a flow will result in overheating in a system designed for the optimum flow rate. You are just racing past the cooling section before returning to the heating section.

You mention 90 degrees which is not outrageous, I would be fitting a new thermostat for a few dollars and giving that a go before chemical or physical attack on anything else.

The thermostat has no effect on pressure, only flow. It does not change water direction as it is merely a gate in the line that opens and closes according to temperature. They start to open about 75 degrees on the old motors and are fully open by about 90 degrees. If you go down a long hill the engine will cool and the thermostat will close until engine temperature rises as you start up the next one. It is constantly going in and out changing the water gap to maintain the optimum temperature.
Lang

Lang wrote: As mentioned above the thermostat regulates the flow by opening and closing. If you take the thermostat out it will allow full flow through the system passing the water through the radiator too fast for heat transfer to occur. The water must be up against the cool sink of the radiator long enough to lose heat to the cooling fins.

Against what might seem logic, too fast a flow will result in overheating in a system designed for the optimum flow rate. You are just racing past the cooling section before returning to the heating section.

You mention 90 degrees which is not outrageous, I would be fitting a new thermostat for a few dollars and giving that a go before chemical or physical attack on anything else.


The thermostat has no effect on pressure, only flow. It does not change water direction as it is merely a gate in the line that opens and closes according to temperature. They start to open about 75 degrees on the old motors and are fully open by about 90 degrees. If you go down a long hill the engine will cool and the thermostat will close until engine temperature rises as you start up the next one. It is constantly going in and out changing the water gap to maintain the optimum temperature.
Lang

Lang I believe you are 100% correct if the water flows to fast over the radiator it doesnt get time to cool it properly, I have been told this a few people older and wiser than me


Paul

Wedgie, How accurate is your temp Gauge?
Put your thermostat in a saucepan of water on the stove & see if Its' working Bung the Kids thermometer in there too, so you know What temp It opens..
& also buy one of those cheaparse infrared Thermometers of ebay

PS: I also second Chocs Questions regarding your radiator.........

Wedgie

Did you notice if the oil pressure dropped considerably as the engine got hotter (You would have to drive for some distance to warm everything up). On those engines 10 psi is good at cruise revs and down to 5 psi is acceptable.

If your temp gauge is showing high but nothing is happening dramatically in the engine such as boiling, smoking, smelling or hot to touch or dropping oil pressure, Hayseed might be worth listening to and try another gauge as all these things are connected.

Common sense says try all the easy/cheap things before ripping out radiators, replacing water pumps or pulling heads. Cheap gauges and thermostats can be bought for a few dollars and take a few minutes work. Back flushing the radiator with a fire hose in the bottom hose can (not necessarily will) perform miracles.

Lang