Best Procedure for Flushing Cooling System


I Just changed the Oil Cooler last night. Installed new oil cooler, put a rubber plug into the port that the hose connects to from the oil cooler to the engine block. Took of thermostat housing to remove thermostat , only to find there was not a thermostat in there, replaced housing. ( I did order a new thermostat which should be arriving Monday (90$ -ouch). Put in a half a bottle of dawn dishwashing liquid in Radiator and put a hose into radiator that I wrapped with electrical tape to try to creat a seal for input into the radiator cap and began to run water under city hose pressure to flush. Mind you the truck has sat for a few months due to lack of time. it took almost minute, maybe less then the hose going from the block that is disconnected to the oil cooler, appeared to take a dump, looking like a terd coming out from the hose, then it went to just sludge and a sudsy mix. I did that procedure 4 or 5 times each time putting in more dawn dish soap. Then disconnected the bottom radiator hose and put in the last 8 to 10 oz of dawn using up the entire quart. I plan on doing it again, tonight
and tomorrow I am borrowing a kerosene powered power washer, he said I can just use the hose to run hot water through.
Is there a better location or an alternate location to start the flushing process and / or a better hose to disconnect from to help this process of flushing ,before I put it back together when I get the new thermostat housing in the next few days..?
THANK YOU in advance:thinking: I have been told I over think !!!!


Well-known member
First DO NOT USE dish soap inside the engine to clear oil and crude deposits .
The surfactant in the soap will cause it to foam!

Use dish washer detergent (low surfactant) in the cooling system with fresh water, filling system and then taking the van for a cab up the street until it gets hot.
Drop the entire contents out of cooling system which means removing the screwed in freeze plug at the back of the block (passenger's side) and lower hose.
I use a Snap On rounded nut socket to grip the shallow nut sections and a knuckle bar to remove it which will cause a loss of all the coolant "mix" the block cooling jacket.

Repeat the procedure until the system is clear of oil deposits.
Do final flush with Prestone cooling system flush solutions, flush again and then fill with MB A/F dilute to strength with distilled water or Zerex A/F premixed.

I always install a new threaded freeze plug with thread sealant once the flush procedure is completed.

This procedure has proved to be very beneficial to clearing oil from Chev mid sized cars with the 3.1 V6 engine which was notorious for allowing engine oil to get past the inlet manifolds and contaminate the cooling jacket!
Method works well on Landrovers too!

Aqua Puttana

Poly - Thread Finder
First DO NOT USE dish soap inside the engine to clear oil and crude deposits .
The surfactant in the soap will cause it to foam!

It is not too late to just use dishwasher soap. It will quickly knock down any foam from the Dawn.

I worked maintenance at a boutique hotel where the suites had automatic dish machines. More often than would be expected a guest would put hand dish wash soap in the machine. The housekeepers would find a real mess.

I was called to one of the incidents. As an experiment I added proper dish machine powder to the mess. It is counter-intuitive to add more soap, but it knocked down the suds immediately.

Another caution is to not use any individual pouch dish machine soap. The little plastic like pouch can stick to things after dissolved. My son learned that when cleaning his vacuum cleaner filter in the dish machine. If pouches are all that is available then slit the pouch and pour out the contents. Discard the pouch.

:2cents: vic


UK 2004 T1N 313CDi
As an experiment I added proper dish machine powder to the mess. It is counter-intuitive to add more soap, but it knocked down the suds immediately.

:2cents: vic
Or... add 1 or 2 drips of Spa/Hot Tub 'No foam'. It immediately kills the foam. I use it in our carpet shampooer to stop it foaming and raising the switch off float.


Edit to add - I use no foam in the shampooer waste tank, not in the clean water side!
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Thank You all for the Reply's
I was able to borrow a kerosene powered power washer from a Great Friend.. I took the power washer hose that he has and instead of putting on the power washer wand , it had what looked like a Milton quick release plug for his power washer wand.( My Friend comes up with an IDEA ! ) He looked at the metal port coming off the back of the new oil cooler, and its hose that goes back to the block that we left disconnected for flushing We took an older hose with the same power washer quick disconnect since it had a cut in the hose. We cut off a 10 foot section of hose leaving on the quick disconnect. We Took a 6 inch piece of PEX Tubing, attach the pex tubing to the hose that was supposed to be connected to the oil cooler port that goes back to block and with hose clamps we used the 10 foot section of power washer hose and pushed hot water back into the block. First making it drain from the bottom radiator hose. after 15 minutes of flushing. power washer stalled and needed kerosene refill . I reconnected the bottom radiator hose and then we continue to push hot water to go in to the block and now out drain out of the top of the radiator with the radiator cap off.. We continued to use 180 degree water for another 10 or 15 minutes, then shut off heater on power washer and then just ran cold water for another 15 minutes.
Put old thermostat back in refilled using only a 1/2 gallon of Coolant and water. Will continue over the next couple weeks to drain and change coolant for piece of mind. Before using the proper amount of coolant due to price of coolant. I then Changed the oil and filter ,I put in mobil 1 synthetic 0-40. Then went for a test drive, I had to add some more coolant, less then quart, continued driving and it got to operating temp. Went to gas station added power service diesel fuel additive and filled tank.
Now so far so good.
BUT HEATER FAN NO LONGER WORKS. But NO MORE black ice cream dispenser out the top of the radiator with the cap off...
Will take a look tonight after work to see whats up with the heat fan control. with winter coming. Going to need the heater fan to work..
Thank You , This Forum IS GREAT. !

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