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Bypassed heater core- coolant flush

7K views 7 replies 5 participants last post by  cboring 
#1 ·
I'm sorry if I may sound naive--

I had a problem with a coolant leak and I ended up tracking it down to my heater core. It wasn't leaking into my car, but rather pooling under my battery behind the firewall and draining intermittently. I ended up bypassing my heater core altogether.

My question is, since the bleeder hole is covered and hoses are connected, how would I go about flushing the cooling system??

It's necessary because at some point I had been leaking so much coolant I eventually switched over to green prediluted coolant instead of G12 And I'd like to go back to the G12 without paying $169 for the dealer to do it. (I'm a broke college student)
 
#3 ·
With the engine cold, start by removing the overflow tank's cap and opening the drain plug at the bottom of the radiator. Pull the bottom radiator hose at the "quick release" connection, if you like. If your thermostat is old, you may want to replace it, as well. You may need to remove the alternator to reach the thermostat on a 1.8T. On a 30-valve V6, you might as well go ahead with a full timing belt and water pump replacement, because the thermostat is buried down in there.

After the coolant has drained, refill and drain the system a few times, starting with tap water and ending with distilled after the tap water comes out clear.

Do not worry about using the weep hole on the heater hose -- I never do, anyway. After reassembling everything, fill the system with a 50/50 mix of coolant and distilled water. Remove the overflow tank's mounting screws and hold it as high as you can, while you pour your new coolant mix in very slowly, to minimize formation of air bubbles in the cylinder head.
 
#4 ·
You would flush the coolant the same way everyone else does. Disconnect the 2 hoses, add a lenght of hose and run the other end into a bucket. Rinse, repeat.
 
#6 ·
Don't you love those plastic connections? If you need Heat again ever in future just cut some smaller size pvc pipe to fit inside the existing by JB Welding it. Just basically a stent to alleviate the hole. Probably a good idea by that time to flush both ways on your heater core too since most of the crud is drying out. I have used CLR on 3 different occasions to flush and have left in hose for about an hour on each. Still holding up with super Heat. Believe me if you have seen the Utube video on replacing heater cores you will want to do this first guaranteed!
 
#7 ·
I definitely have no interest in ever replacing my heater core. I originally wanted to repair the pipes, but my mechanic offered to bypass it for $4.00. Plus, heat isn't really a necessity here in SoCal so it's not like I'll be missing it! Pesky plastic parts- next project is replacing my timing chain tensioner pads :icon_eek:
 
#8 ·
Thank you so much for your detailed response. I plan on tackling all three. I'm not sure of the condition of my water pump but, I have to do an upper engine tear-down to check the pads on my timing chain tensioner and replace all the gaskets due to plastic found on my oil pan. BIG weekend project.
 
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