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Heater core flush questions...

xjwisconsin

NAXJA Forum User
I have determined by holding the upper and lower hoses on my heater core that I have some blockage... It looks like we are going to have a couple of days of warmish weather and I would like to try and backflow while I have the chance. So My questions are as follows...

1. Is 3/8" a correct measurement for the id of the hoses (id like to rig up a couple of couplers to connect to the garden hose)?

2. Can I, and, or, should I introduce a solvent like white vinegar or CLR into the core to help loosed likely deposits?

3. Any other tricks?

thanks much
 
Vinegar would be a lot safer than CLR. Be very careful with a garden hose, as it can over pressure the heater core and blow it apart. City water can be as high as 70 PSI, vehicle Cooling systems typically run at no more than 16 psi. I would just the hose loose right at nipple or short hose and flush it gently, not under sealed pressure.
 
I was going to use the hose fittings to attach an "x" Length of hose to allow me to direct the flush flow out of the engine bay and into a catch bin.

Is the core made of aluminum?
 
I was going to use the hose fittings to attach an "x" Length of hose to allow me to direct the flush flow out of the engine bay and into a catch bin.

Is the core made of aluminum?

The newer ones are aluminum. Not sure what year it changed. My old Renix ones are copper.
 
One is 1/2" and the other 5/8" IIRC.

I wonder if that varied between 1985 and 2001?

I recall some 3/4 hose in there somewhere too, but I forget what the HC ones are.
 
I said IIRC. Could have been 5/8" and 3/4". I know for damn sure it ain't 3/8".

LOL, or 1/4"!!!

I think from one end (the water pump) to the other end, bottle and heater core, they used every single size except 1" and 3/8", LOL!!!! Most fun I ever had was my first time replacing that mess!@!!!@&^$##$#@ I even recall a 7/8" IIRC at the water pump?
 
gotcha, I stupidly forgot to say this is an early 98. I got the 3/8 from some old thread, but I was trying to confirm sizes so I dont need to make a bazillion trips around town in my wifes car.
 
don't use CLR, it is destructive to almost everything in the cooling system

if you are just going to flush the heater core only, just use a garden hose on medium pressure, and move it back and forth between the pipes. dont use a lot of pressure or you will blow through a solder. also the pipes are different sizes, but the washer in a typical garden hose fitting will snug up against the pipe alright
 
I was leary of the CLR, saw it mentioned. Vinegar I figured wouldnt be all that bad though. Im hoping that by back flushing it on low with the garden hose will be the cure though
 
don't use CLR, it is destructive to almost everything in the cooling system

if you are just going to flush the heater core only, just use a garden hose on medium pressure, and move it back and forth between the pipes. dont use a lot of pressure or you will blow through a solder. also the pipes are different sizes, but the washer in a typical garden hose fitting will snug up against the pipe alright

+1 on all of this.
 
Just finished flushing. Took it for a ride and it does feel considerably warmer. Felt both in and out hoses, and the in feels warmer than the out. I flushed a gallon of white vinegar through and some cloudy junk came out. On a side note I found that a length of 1/2" pex pipe fit perfect in the lower hose and a length of 3/4" pex pipe fit snugly in the top hose. Using them allowed me to direct the water out of the engine bay and into a couple of catch bins.
 
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