Hot engine flush


Old 07-04-08, 09:36 AM
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Hot engine flush

Over 25 years ago I was taught by the best of the best to flush out my engine at full op temperature.
Method: Remove the upper rad hose and put a garden hose into the rad and allow the cold water to gently flow through the thermostat as it cycled open and closed effectively flushing out all of the old coolant and junk from the entire system heater and all untill the waste water was clear.

My concern is that old method was based on engines built before the 1980's. (Iron block and head V-8's and straight 6's).
Is that old flush method bad for modern engines with thin walled blocks and alluminium heads?

I am going to flush the coolant system, replace the thermostat and hoses on my 98' Windstar tomorrow and may use this method but I am afraid of cracking the block or upsetting the head gaskets.

I may just pull the thermostat and flush it out with the engine cold and off to be safe.

Any knowllege on this........................?
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Old 07-04-08, 01:14 PM
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I grew up with never put cold water in a hot engine. But there are probably exceptions to that as far as how you do it.

The '98 Windstar 3.8 had problems with the head gaskets blowing. I can't remember if it was a head problem or just the gasket design. Supposedly after '99 the problem was fixed. I had the 2000 model and no trouble.
Old 07-04-08, 03:05 PM
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If you were to pull the thermostat and do the garden hose flush it would be pretty effective. Put the hose in the thermostat opening when you get the t-stat out and put your hand around the gaps. All the old coolant will come out the other end. Do it with the lower hose off and catch it from the water pump inlet. Then flush radiator from top to bottom. As noted, not generally a good idea to introduce cold water into a hot engine.
Old 07-05-08, 04:16 PM
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OK, OK, I know not to dump cold water in a hot engine.(I left out a few small details)
This method allows the the cold water to gently mix in the radiator first with hot water so when the stat opens it is already hot and periodicaly dump about half of radiator and then pop the lower hose back on and slowly fill with clean water. Repeat until clean.

But to be safe I'll just pull the stat with engine cold and flush.
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