heater core flush (nf)

[Raf]

the heat in my jeep sucks. it's barely lukewarm. the inlet hose going to the core is hot, the outlet cool. so i suspect a heater core blockage. seems like a fairly straightforward procedure disconnect the hoses and pump water through the core backwards.. then forwards, repeat ad nauseaum till the water is clear.

 

my question is are there any chemicals that i should use to help the flush and do i risk creating problems (ie. leaks) doing so. replacing the core is waaaay too much work than i am prepared to do. i'd rather plug a tiny heater in via an inverter

[4thgen]

Have you checked to make sure that your heater switch is fully opening the valve that allows coolant into the heater core? In civics(my car) the cable has been known to stretch over time and cause that problem. Have you ever used that "radiator leak sealer"? It has been known to plug up heater cores pretty good. I havent tried any of the commercial products (but they do exist), hopefully someone else can give a review.

[irishfield]

If it is actually clogged raf... try putting CLR to it.

[Raf]

i have used stop leak recently and i suspect that is what turned the 'partly' clogged 12 year old core into a 'mostly' clogged core. i will investigate the switch/valve too. i'm guessing there's some vacuum lines part of the equation here as well. (97 cherokee)

[mikemo]

Hey Raf.

I had to have my thermostat replaced at least 3 times on my 89 cherokee. That always appeared to fix the luke-warm, almost cool temps coming out of the vents.

Edited November 21, 2008 by mikemo

[Raf]

thanks mike, t-stat was replaced 2 days ago. old one was sticking open a bit. jeep now gets up to operating temp quickly.

[Tybo]

Raf, Theres a good chance you are going to need a heater core.

That stop leak is nasty stuff.

It binds itself to the calcium build up and plugs every thing.

A flush may work. It all depends on how plug it is.

[Raf]

tybo, hopefully a flush helps.. even a little.

 

the entire dash needs to come apart in order to get the core out, it's a 6-8 hr job "by the book". i'm neither paying someone to do it or doing it myself. rather invest in warm clothing.

[Bernie]

Both hoses should be within 2 or 3 degrees of another in a good working system.

To flush I very carefully use pure muriatic acid. I take off both hoses and install a length of heater hose to each fitting. Putting on some gloves and a safety face shield I pour in pure muriatic until it runs out level with the outlet. I wait for a few minutes .Then I slowly add some water to flush it out. Then blow it out with some shop air. Works 90% of the time on the first try. Sometimes need to repeat the process. Have never burned through one yet but there are guys that it has happened to.

[irishfield]

Exactly how I've done them before Bernie and why I suggested CLR to Raf. It will eat the calcium and hopefully the rad sealer stuff (since it's usually just oatmeal anyhow!)

[Raf]

add a bit of black pepper to the oatmeal too.. (hey, it was around & worked)

 

i'm a little hesitant working with muriatic acid, but i'll give the clr a shot.. let it sit in there for a few minutes?

Edited November 21, 2008 by Raf

[irishfield]

Raf CLR won't eat anything in the core... but it should eat thru the gunk in there.

 

I'd pop the lines at the firewall going to the heater core... put a hose on the outlet side.. put a funnel on it and pour in the clr.. let it work thru and bubble out the other side. Then let it sit in there for 15 minutes to 1/2 an hour and flush with a garden hose.

 

heck try just flushing with the hose first to see what happens before getting to involved.

Edited November 21, 2008 by irishfield

[BillM]

I replaced a heater core in a buddies 96 Jimmy a few months ago..

 

What a horrible horrible job that was....

[Bernie]

Never used CLR before but I suspect it must be a mild acid to dissolve calcium. Let me know how it works out for you.

Bill M. some are easy as pie others are a dude.

Edited November 21, 2008 by Bernie

[BillM]

Bernie, I guess it's one extreme or the other. The entire dash had to come out of the Jimmy All for 5 mins of work for the replacement..

[Wild]

There should be no calcium deposits if you use distilled water, look into the rad cap opening for the presence first otherwise suspect rust. But the question Raf, why did you need stop leak in the first place?

[Raf]

Wild, to make it short; was on the 401 stuck in traffic. auxillary fan comes on, aux fan blade snaps, aux fan blade now projectile - punches pin-hole in rad. had some stop leak in the truck poured in to get under way (disconnect teh aux fan and waited for traffic to die down)

Edited November 21, 2008 by Raf

[Wild]

Ok as long as you did not use it to seal the cores due to corrosion. Give a reverse flush a try then, I use a hose fitting with air injection and it blows out lot's of crud.

[davidd]

I've spent some time on the net today looking at various options for unclogging a possibly clogged heater core in my 98 Volvo. The driver's side gets cold air and the passenger side gets hot air, so I'm expecting it to be a partially clogged core. It is cold here in Minnesota now, so I was looking for relatively easy options that included reduced risk of frostbitten hands.

 

I figured I'd share a couple ideas other than what has already been mentioned.

 

One idea is to swap the hoses on the heater core. That will use the pump to do the dirty work for you. The crud will still be in the system, but not blocking the core. A full flush is probably recommended at some point after doing this, but might be an easy way to get you up and running quickly. The recommendation (from others) is to swap the hoses and run for several minutes with the heat on high and then swap the hoses back.

 

The other plan is a product called RMI-25. You can google it to find one of the online places to purchase it. Apparently local shops don't carry it. Goes for about $10/8 oz bottle.

 

This is a product that you can add to the coolant and it will slowly unclog and open up the narrow passages in the system (radiator, heater core, pump, engine block). It somehow keeps the junk in suspension and will supposedly end up migrating it to the overflow tank, where you can remove it if you want. From the pictures, it will look like a slimy material.

 

Benefits of that approach is that you don't have to mess with the hoses, antifreeze spillage, etc. Might take a couple weeks to complete the unclogging, according to what I've read.

 

I ordered a couple bottles today and I'm going to try this approach.

 

This product can also be used as preventative maintenance once or twice a year to keep the system clean.

 

Even though it keeps the junk in suspension, I'm still planning on having the system emptied and refilled when time allows. And if this stuff works, I'll probably start using it for preventative maintenance.

 

I don't have any stock in the company. I don't even know who makes it.

 

Prestone makes a Super Radiator Flush and Super Radiator Cleaner. The Flush involves emptying the system, putting the stuff in, and letting it run for 10 minutes and then emptying and refilling again. The Cleaner is the same process, but you leave it in for 3 to 6 hours of driving (can be intermittent) before flushing it out.

 

I figure the RMI-25 is the same idea as the Super Radiator Cleaner, yet you can leave it in there indefinitely and don't have to go through the flushing procedure right away if you don't want, so that's what I'm going with for now.

 

David

[Bernie]

One idea is to swap the hoses on the heater core. That will use the pump to do the dirty work for you. The crud will still be in the system, but not blocking the core. A full flush is probably recommended at some point after doing this, but might be an easy way to get you up and running quickly. The recommendation (from others) is to swap the hoses and run for several minutes with the heat on high and then swap the hoses back.

 

David

 

I would not recommend this. Better the restriction remain in the heater core than end up in the radiator and end up overheating your engine.

Off the shelf radiator flushes are mediocre at best. Another waste of time and money.

[Raf]

hey davidd thanks for popping in.. how's the fishn in MN?