Back flushing the engine? Ever heard of this or tried it?

[White Spyder]

Was chatting with an old gent that said he used to work on old flat heads for a living. He told me that he used to back flush the coolant system/engine by putting a water hose in the bottom of the engine and flowing water the opposite direction of normal flow to clear deposits from the systems that may have become wedged int a passage. I have never heard of this. Has anyone else heard of this or tried it? Would it damage anything?

[JerseyHarold]

I've heard of back-flushing but don't have any personal experience with it.  Prestone used to make a back-flush kit for that purpose.

[plymouthcranbrook]

I have back flushed cars years ago but stopped when an old mechanic told me to be careful because it was possible that the materials loosened but the back-flushing might be caught in the heater core due to the small tubes and plug it up.

[P15-D24]

Factory manual covers the correct technique. 

[Plymouthy Adams]

when using the lower radiator hose as an inlet you are 'still' flowing in normal coolant flow direction...back flushing requires you to reverse the flow...often done with pressure and thermostat removed..again though..these older cars are not accustomed to pressure..the heater will be very subject to damage especially if there is a partial restriction there already..what the ole man was simply describing is a fast flush ...usually one will remove the thermostat and top radiator hose...with the radiator full, you start the engine and then regulate the input of water from a hose into the top of the radiator and match the flow of the water being pumped from the engine...with thermostat out and heater valve open..you should also be moving clean water though it..this will remove most loose particles and discoloration in short order but heavier residue and sediments are not going to be greatly affected.

[Eneto-55]

I know that some say you should not remove the thermostat for the summer, but my dad always did.  He would flush the system (like Plymouthy Adams describes), then run straight water until Fall, when he would test the thermostat for proper operation, and re-install it.  (This was of course before having a car with AC - he stopped doing it sometime before - maybe after the last flat head.)  I should also say that our water was pretty low in minerals, and he may have added a rust inhibiter.

[Lloyd]

I remember back flushing was also popular back n the 60's and 70's. At that time it was the accepted way to flush a cooling system. Could even buy back-flushing kits at K-mart that would let you hook up a water hose to a heater hose as I recall. Haven't heard about it in years, seems it went along the roadside as a maintenance op.

[busycoupe]

I worked in service stations back in the early 70's. Flushing the cooling system was one of the "regular" services we performed.  I don't remember the details, but it involved putting a plastic tee in one of the heater hoses to attach a hose to.  I think the purpose was to flush out the old coolant more than to remove sediment, but frequently the coolant coming out would be brown.  Of coarse we then filled the system with a 50/50 mix of new coolant.  We weren't at all careful about where the old coolant went, it just went all over the ground and was washed into the storm drains.  The environmental police would be all over that today.

[White Spyder]

Hear is my thought. When I first got the car I had to remove the water distribution tube. I found a chunk of hardened material wedged into the opening of the hole at the rear of the tube. If one were to do as mentioned above and back flush through the heater line connected to the rear, might that type of blockage be pushed back out the larger end of the tube?

Just thinking........

Edited April 4, 2015 by White Spyder

[Lloyd]

Hear is my thought. When I first got the car I had to remove the water distribution tube. I found a chunk of hardened material wedged into the opening of the hole at the rear of the tube. If one were to do as mentioned above and back flush through the heater line connected to the rear, might that type of blockage be pushed back out the larger end of the tube?

Just thinking........

 

Id say its possible, but Ill bet its also a pretty hard clunk of deposit and that if it does come lose it may just get lodged somewhere else. For it to travel all the way thru the system and out would be a surprise.

Also a garden hose may put out enough pressure to dislodge it but outside faucets don't really put out a lot of pressure. Some of the engine flush stuff they have at the auto parts stores say they dissolve deposits. Suppose to add it then drive around, drain and refill. Never used any but it might be a consideration using before the flush. Get a piece of the hard deposit stuff and put it in some and see if it dissolves.

[White Spyder]

Lloyd,

Threw out the chunk when I did the work a while back. I am not in the need of doing this at the moment. I had only asked as I had not heard of a back flush but when I considered what I had found when I removed the tube it got me to thinking about those that might want to try it prior to struggling with tube removal and general discussion.

Edited April 5, 2015 by White Spyder