Hey Everyone,

I have a 91 SR5 pickup that is not having any problems, but I have never changed the coolant and I have had the truck since 2001, so I want to do that.

My question is, back flush or regular drain/refill?

Seems like in older vehicles that have not been back flushed regularly and have had years to create sediment/scale/etc... that back flushing might actually do more harm than good by washing a bunch of crap into the radiator. I know it's suppose to be purged out the top, but seems like tiny bits of particulate matter could get lodged in the radiator and make it less efficient, or worse ... I'm thinking maybe an old fashioned drain/refill might be better.... maybe just pour a couple gallons of distilled through it before refilling. Am I wrong? Are people back flushing their old rigs without problems??

Thanks for any input!!

 

Lots of threads how to flush your cooling system on Yotatech. It's easy.
Flush it, not back flush it.

Basically drain radiator. Refill with water. Drain radiator.
Remove top hose. Put hose in top of radiator at cap. Turn on heat. Run engine until hot and tstat opens up. Let run until all clear water coming out. It's flushed. Refill.

:wabbit2:

 

(Very cool avatar!) Thanks for replying and I'm glad I asked. I was considering a Prestone (or similar) kit with the T for the heater inlet hose, etc, per this method http://www.youtube.com/watch?v=tVWzn...feature=relmfu but I'll stick with the safer, standard method of just flushing the radiator and not back flushing the entire cooling system.

Out of sheer curiosity, have people run into problems back flushing the entire system?

 

Back in the old days There used to be what was called a power flush which worked pretty well with newer cars .Shop water pressure into the cooling system.

But when people started having vehicles on the road 15 plus years old they started blowing radiators apart.

I have no clue if this is still done or not.

The way i flush is just drain the system of coolant fill with water run till the thermostat opens and repeat till the water comes out clean depends how long it was last done.

I have done it 5 or 6 times to get things clean

 

The longer coolant remains in the engine, the more lubrication & cooling properties it loses. I STRONGLY recommend changing at least every 2 years.

That said, good advice above.

 

Thanks wyoming9 and TNRabbit, and yes, I do need to do it every two years.

Here in So CA the water is extremely hard and full of mineral salts, so I will be using distilled water for flushing/cleaning.

But just so I'm clear, you're saying it's ok to fill the rad with 100% distilled and run it until the t-stat opens, then drain and repeat until it flushes clean, before adding the 50/50 mix, right? I am assuming I leave the cap off, right?

And one other stupid question.... how do I know when the t-stat opens? Aside from feeling the lower radiator hose? Or is that the only way?

Thanks again guys.

 

As long as it is not below 32 degrees F you should be ok.

I always put the cap back on

It is the upper hose that tells you when your thermostat opens. I can also tell by the drop in the temperature gauge

Just be very careful draining the hot water/coolant out of the radiator if you have not removed the stupid splash shield under the vehicle now is a good time.

I just use well water here with my flushing unless you have a free source for distilled water

Back in the old days lots of people just ran plain water from spring to fall.

 

Thanks a bunch, wyoming9!

FTR I buy distilled from a vending machine ("Glacier Water") outside the grocery store for 25 cents/gal. I have to get it regularly for my fish tank, so I have (2) 5gal jugs I fill every couple weeks.

Thanks for correcting which hose I need to check if the temp gauge doesn't drop, and great tip about the "splash shield." (Had no idea people used to run straight water in their rads!)

Really appreciate the help. Beers (or favorite libation) on me...

 

Running 100% water is fine for a little while. The only issue would be it doesn't provide sufficient lubrication for water pump seals so over time could contribute to premature pump seal failure. Run the piss out of it for 10 mins then drain & refill. Be sure to park uphill when you refill to burp all the air out~

 

Thanks for that clarification, TNRabbit....! I might also use one of those Lisle spill-free funnels in addition to raising the front end. They look real handy for burping.

 

tagged, good info

 

Just for the record I put a tee in the heater hose just before the heater control valve.

All i use this for is to bleed the cooling system as it is the highest point.

Works great no more water pockets.