A friend of mine is about to flush his cooling system. He has no visible leak at the heater core but suspects one as there is some humidity in the car at the passenger side.

we were about to flush the heater core as the coolant was full of rust.

do we increase the risk of leak ?

maybe dirt fills small holes ?

what is your experience.

I keep in mind : if it works don’t fix it.

thanks

 

I have never had one leak because of flushing it.

 

it can, if you use too much pressure. just a hose flush should suffice, don't go blowing 100psi of air through it, or you will blow holes in it.

also, i know most are aching to throw some CLR or other abrasive cleaners. if you're gonna use it, just use a mild solution of CLR or simple green. don't go crazy here either.

flush backwards for most of it, then a quick forward through, and backwards again. this should lift up any other debris. just take your time. it may take a while.

the warmer the water, the better. i know most outside taps are cold water. also, keep the pressure washer away from it. lol

 

That's good advice. Do it that way.

If the heater core does leak a little more afterwards, consider that a 'good sign' heading into winter. Better to change it now than have it *really* leak bad middle of Jan! No shortage of "How To's" on this site for changing a heater core.

 

Agree with the others.

Flush each side with a low pressure garden hose.

Do NOT use high pressure.

If it leaks after a low pressure flush, then it means it was ready to start leaking either way and it could not be avoided.

Good luck and keep us posted!

 

I recently flushed mine and it definitely exacerbated a small leak that I suspected. if you suspect leak already then it needs to be replaced anyways. my recommendation is to use a garden hose at about 1/8-1/4 of a turn...VERY LOW PRESSURE. if it leaks after that, then it was going to happen sooner than later anyways. Let me know if you have any questions about replacing the heater core... I just did mine last week.

 

I believe you need to use moderate pressure to "Force" out the crud (backflushing mode). You can't just drizzle water in there ...put the hose on and let it blow out the crud. If your buddy thinks he has a leak, well, he might as well start planning for a replacement and watching videos now ..or track down someone who can do it within his budget. It only gets worse.

The worst part of the job is the time spent 'thinking how it's going to suck'. The actual doing part once ya get started isn't that bad, IMO.