[GSB]

Originally Posted by leif20

You know I was just thinking that. Driver's side heat is ok but passenger is tepid. I am sure there are still blockages in the core. I would expect no temperature deltas if the core was operating correctly. I did NOT fully pressurize but I did use maybe 1/3rd the pressure of the garden hose. I was anxious and worried to blow out the heater core and render my car undrivable. Garden hose pressure is 40-80psi? I am worried this will burst the heater, given typical coolant system pressures are 15psi ish.

I might speed up the process and repeat. Given i've already done it once, I don't think I need to run vinegar again for 2 hours. Maybe CLR for an hour. How much should I open the hose? I do have a regulator at the barb so i can carefully control the flow there.

Yes, a valid concern. Household water pressure is 40-80psi. That's why you never want to expose a blocked core to instant pressure from a hose.

However, it is important to note that the water pressure inside an open hose, flowing fully with no restriction at the end, will be almost 0. Only if you block the end of the hose, will the pressure inside increase rapidly to the max.

That's why it's recommended to first dissolve the gunk that binds any sediment, then use a nozzle with flow control to gradually increase flow until the core is clear of sediment and able to handle the full flow from the hose.

To prevent accidental over-pressurization, I pulled the pump tubing out of the bottom connection of the core, leaving a tube only in the top of the core. Then I made a fist around the loose end of that tube and the nozzle of the garden hose. Any sudden over-pressure situation will burst out of your fingers rather than the core. A handful of sediment popped out of the core and a second later, the core was flowing a fully open nozzle with hardly any pressure felt in my fist.

Like this... Leave a gap between tube and nozzle, then squeeze hand shut to seal...

[sepling]

Originally Posted by GSB

Nice! Thanks for sharing. I'm glad it went well for you. Cool idea with the filter. During your step #4, did you also pressurize gradually with a garden hose? I found that some of the loosened particulates were so heavy that the low-pressure pump alone could not blast them out.

I did but didn't push it too hard as I was terrified of blowing a seal or causing a leak. Just a couple short bursts with the hose at the end of the process and not at 100% water pressure. I actually think the CLR was dissolving some of the bigger flakes. If I got something big enough in the filter to pick out with my fingers it would just sort of disintegrate when I touched it.

[leif20]

Looks like i have to repeat the job. Hopefully will go quicker this time. I'll use the superclean and CLR, and then the hand-regulated garden hose. Brilliant idea there!

I guess simple green and vinegar weren't strong enough.

sepling did you use any hot water in the process?

[sepling]

Originally Posted by leif20

Looks like i have to repeat the job. Hopefully will go quicker this time. I'll use the superclean and CLR, and then the hand-regulated garden hose. Brilliant idea there!

I guess simple green and vinegar weren't strong enough.

sepling did you use any hot water in the process?

Yes. Both my degreaser and CLR flushes were hot water though it cools down pretty quickly when circulating the solution. I ran the CLR for probably two hours switching the flow direction every thirty minutes or so. As long as you aren't leaking where the vinyl tubes enter the heater hoses, I see no reason why you couldn't run the CLR for much longer, but only if it's a last ditch effort as it is etching the aluminum.

[leif20]

Originally Posted by sepling

Yes. Both my degreaser and CLR flushes were hot water though it cools down pretty quickly when circulating the solution. I ran the CLR for probably two hours switching the flow direction every thirty minutes or so. As long as you aren't leaking where the vinyl tubes enter the heater hoses, I see no reason why you couldn't run the CLR for much longer, but only if it's a last ditch effort as it is etching the aluminum.

Interesting. CLR is NOT recommended for aluminum, I guess the idea is to run it only for as long as necessary? I do get some leaks from the vinyl hoses but I didn't use masking tape. Maybe I will do that first.

How did you heat up the CLR? Mix with hot water?

GSB After all the chemical treatments, Are you suggesting to do the pressurized back-flush first, meaning running it backwards through the core to blow out the sediment? Then once it's flowing more freely, flush in the forward direction as well? Intuitively this makes sense to me, back-flush with pressure to remove the blockages.

Thank you both for all the help! If this doesnt work the next time I'm going to start thinking about replacing the heater core.