Looking for advice on flushing the rear heater core on the 1996 6.5 diesel Suburban.

[jrsavoie]

Looking for advice on flushing the rear heater core on the 1996 6.5 diesel Suburban.

I have a black and a green hose going to the T's from the back of the Suburban. Which hose is supply and return?

Or I have a top and bottom T - Which T is the supply and which is return?

There was one line coming off the thermostat housing to one of the T's. Is that the supply?

How much pressure can be used to flush the system? 15lbs? 8 lbs.?

It seems to me that it is Ok to back flush the system as well? Is this correct?

I know there are some old threads on this someplace, but I have not had time to look yet.

[DennisG01]

I'm not sure if this thread gives you what you want, but in the thread I was talking about flushing the core. http://www.thedieselpageforums.com/tdpforum/showthread.php?t=39910&highlight=flush+heater

I believe I marked which lines are "to the rear core" and which are "return" directly on the lines. I can check tomorrow. Backflushing, I suppose, would be ideal, but I'm not sure how much it really matters. In essence, it's just a long loop. If I recall correctly, I just hooked a garden hose into one of the hoses going to the rear core and turned it on full blast.

[jrsavoie]

I'm not sure if this thread gives you what you want, but in the thread I was talking about flushing the core. http://www.thedieselpageforums.com/tdpforum/showthread.php?t=39910&highlight=flush+heater

I believe I marked which lines are "to the rear core" and which are "return" directly on the lines. I can check tomorrow. Backflushing, I suppose, would be ideal, but I'm not sure how much it really matters. In essence, it's just a long loop. If I recall correctly, I just hooked a garden hose into one of the hoses going to the rear core and turned it on full blast.

I would be scared to hook the garden hose to the system without regulated pressure. Our water pressure goes upwards of 60 lbs.

We also have other considerations - no heat in the shop so I will have to use a filtered antifreeze mix to flush with.

Also our water isn't the greatest. Flushing with our water might cause more issues than not flushing at all LOL.

How much water pressure does your system run?

Thanks

[DennisG01]

I have 72lbs of pressure. As long as you currently have flow, I can't imagine it being a problem as the water is just going to go right through - there's no blockages to build pressure.

Flush it first with the garden hose to take care of 99% of the flushing, then flush the "bad" water out with air to get rid of most of it. I seem to remember just blowing it out by mouth. Then pour AF through - just keep one end higher than the other and gravity can do the work for you (use mouth/air tank pressure to help if you want).

[jrsavoie]

Thanks

[phantom309]

I would be scared to hook the garden hose to the system without regulated pressure. Our water pressure goes upwards of 60 lbs.
Perhaps only turn the tap on a little<>>????



We also have other considerations - no heat in the shop so I will have to use a filtered antifreeze mix to flush with.

Just how cold is your shop?

If the tap is flowing water thru the hose,.then i doubt anything will have time to freeze inside the heater core,.

When your vehicle is running and the rear heat is on,. you will be able to tell just by touch which is feed (hot) and which is return (much cooler)

[DennisG01]

I have a black and a green hose going to the T's from the back of the Suburban. Which hose is supply and return?

Or I have a top and bottom T - Which T is the supply and which is return?


I knew this was an easy answer, but for some reason was a little foggy on it last night. The supply (going to the cores) comes from the t-stat housing. The return line dumps into the top of the radiator.

[jrsavoie]

Perhaps only turn the tap on a little<>>????



Just how cold is your shop?

If the tap is flowing water thru the hose,.then i doubt anything will have time to freeze inside the heater core,.

When your vehicle is running and the rear heat is on,. you will be able to tell just by touch which is feed (hot) and which is return (much cooler)

The vehicle is not running yet. I might be flushing the heater core before the heater is running.

I will be flushing with an antifreeze mix. Hopefully I do not have to flush much. I plan to recirculate to a tank with a filter.

The shop is cold the same as out doors. No insulation, no heat. 16' walls, 32' x 40' Cleary Buildings put a 1' eve VENT all around the top walls. So I have 80' x 1' air gap at the top of the walls. Plus ridge vent. All the heat goes straight out. No easy way to get up and seal stuff off.

Health problems shut me down on finishing the building. No floor - no insulation - no ceiling - not much of anything but a shell and tools

[DennisG01]

I understand you're worried about freezing, but running water won't freeze. It seems like you'll be going through a lot of extra trouble to get a recirculation and filter setup together. Really, all you need to do is stick a garden hose to one of the rear heater hoses (at the T on the engine), extend the other heater hose into a white bucket and turn on the water. The white bucket will show you what's been flushed out.

When you're satisfied it's flushed, just blow into the heater hose to force out most of the water. Then let gravity do it's job and simply pour AF into the hose until you get solid AF coming out of the other hose.

Believe me, there's no chance of things freezing up if you do it this way. I'm a boater (and work on boats, too) - I know all about the steps needed to keep engine blocks, manifolds, AC/Heat systems, head systems, etc. from freezing over the winter.

[jrsavoie]

At 5 degrees things freeze up pretty fast. I would have to string out at least 125' of hose to get to the nearest hydrant. I have a line run to the shed, but no hydrant installed yet.

Our water is probably nastier than what I am trying to flush out.

I can use the sprayer we use for Roundup. It has an adjustable pressure gauge on it.

I can run the return to a bucket til the antifreeze clears up. Any extra anti freeze in the sprayer tank will not hurt anything. We use a propylene glycol mix in our sprayer so we do not have to worry about the pump freezing in the winter,
I use Amsoil propylene Glycol antifreeze so i should not have any issues

With my health issues I never know when I am going to have to give things up and go to the house. Once I had to sit in the shop for about 1/2 hour before I thought I could make it to the house. So I can not get a bunch of water everywhere or anywhere and take that chance. And at this time of year I can not wait for spring.

What does everybody do with their used antifreeze? I've been jugging it and using it for cutting fluid. I don't use near as much cutting fluid as I create used antifreeze though. It works pretty good for cutting fluid, but for certain things I still use regular tap or cutting fluid.

[DennisG01]

Health issues... enough said - sounds like that's a game changer when it comes to being able to getting things done. It won't be 5* all the time - could you wait? Or... it sounds like you're worried about getting partway into the project and then having to stop?

So using the garden sprayer to force the AF through the system... do you think that will move enough volume at a fast enough rate to flush things out? They can build plenty of pressure, but they usually don't move much volume. Another idea might be to use an inexpensive ($20) marine bilge pump. You could set the pump into a bucket of AF and collect the flushed AF in another bucket.

If the grit that you wash out falls to the bottom of the bucket quick enough, you could connect the two buckets together (at the top) with a short length of PVC pipe. So as the "dirty" bucket fills up, it spills over to the "clean" bucket, enabling you to have a constant cycle going. I'm just not sure how fast the grit will fall.

If the grit doesn't fall fast enough and makes it's way to the clean bucket, you could always keep the buckets separate and when the dirty bucket fills, turn the pump off and let things settle, then pour the AF over into the clean bucket and start again.

The township I live in tells us to flush the AF down the toilet. City sewer system - no septic.