How complete of a coolant flush is needed?

[jr1under]

In the FWIW category, I recently learned how to test coolant quality with a multimeter based on the principle that the more contaminated the coolant, the more conductive it becomes. Set the meter to DCV, submerge the red probe in the coolant tank and connect the black to a frame ground. A reading of less than 0.4 indicates acceptable quality. Before flushing my Exp, I got values of 0.7+ and the coolant was filthy and stunk. Now, it's around 0.2 as is my F150's.

 

[jslt]

Quick update, things got a little wild with this project. I did the citric acid flush a few days ago and a TON of crap came out of the system. Of course with my luck, a bunch of that crap was apparently keeping the radiator intact. Midway through flushing out the system, the radiator started leaking. I knew it was a risk of aggressive flushing of an old system, so that one is on me.

I was able to source a radiator and some hoses at the parts store in town yesterday and I was able to get it all replaced. I went ahead and replaced the water pump too while I was at it, though the old pump was in acceptable condition. At this point the only old parts left in the cooling system are the lines to the rear heater and the block. Even with the new radiator, I'm still seeing bits of rust floating around. My plan at this point is to just put it all together and drive it around with distilled water and flush it once a week until it starts looking clean. I'll leave the new heater cores bypassed for now.

Quick question for y'all. I'm putting the dash back together and I can't figure out what this sensor is and where it is supposed to go. It is located right behind the air box. I didn't notice it when I took everything apart and I don't want to miss something on the rebuild. Any thoughts would be appreciated.

 

[jslt]

Some more pictures of the fun I've been having this weekend. Leaking spot radiator (hard to see in the photo). I also yanked the instrument cluster out to re-solder the odometer (it was intermittently turning off). Water pump out, and new radiator in place.

 

[jslt]

Quick question for y'all. I'm putting the dash back together and I can't figure out what this sensor is and where it is supposed to go. It is located right behind the air box. I didn't notice it when I took everything apart and I don't want to miss something on the rebuild. Any thoughts would be appreciated.

After a bunch of googling, that appears to be a capped end of the vacuum line for the defrost actuator. Not sure why its hanging out there, but I think it doesn't impact anything inside the HVAC box. I'll just leave it alone.

 

[Carl Norgaard]

If there's that much rust floating around in the coolant I would strongly suggest that you pull the water pump and check the fins on the impellor. I found mine had rusted completely away. And you might find that you need to jack the front end up to where the upper radiator hose connection at the radiator is slightly higher than the heater core to help with getting the bubbles out.

 

[Petesexpy]

Some more pictures of the fun I've been having this weekend. Leaking spot radiator (hard to see in the photo). I also yanked the instrument cluster out to re-solder the odometer (it was intermittently turning off). Water pump out, and new radiator in place.

How long did it take you to take the dash apart, and how difficult was it? I'm thinking of doing the odometer repair, but somehow I'm not feeling up to it....

 

[jslt]

If there's that much rust floating around in the coolant I would strongly suggest that you pull the water pump and check the fins on the impellor. I found mine had rusted completely away. And you might find that you need to jack the front end up to where the upper radiator hose connection at the radiator is slightly higher than the heater core to help with getting the bubbles out.

I did actually pull and replace the water pump. I figured I may as well do so while the fan and radiator were out and it was easy to get to. The fins on the old pump were nice and solid, so I probably didn't need to replace it, but it seemed like good preventive maintenance.

 

[jslt]

How long did it take you to take the dash apart, and how difficult was it? I'm thinking of doing the odometer repair, but somehow I'm not feeling up to it....

At this point, I've lost track of how much time I've burned on this project That said, getting to instrument cluster out would only require taking the panels around the steering wheel which are pretty straightforward and do not require dropping the whole dash. Having done it once now, I could probably get the instrument cluster out of the car in about 20 minutes. I followed this video. You don't need to take the trim around the stereo out though.

https://www.youtube.com/watch?v=hxGgqPNseTk

I used a magnifying glass and a flashlight to examine the solder joints on the odometer cables. I could see the cracks in the first (left most in my photo) pin and the last two. So far it seems to have done the trick. I also pulled the lamp out for my non-functional air suspension (replaced with springs awhile back) so I don't have the annoying light anymore

 

[jr1under]

Quick update, things got a little wild with this project. I did the citric acid flush a few days ago and a TON of crap came out of the system. Of course with my luck, a bunch of that crap was apparently keeping the radiator intact.

The citric flush just hastened the inevitable which rarely occurs at such an opportune time. Sounds more like good luck to me.

 

[jslt]

The citric flush just hastened the inevitable which rarely occurs at such an opportune time. Sounds more like good luck to me.

I totally agree and that's how I'm looking at it. Just hard to see that glass half full when your previously non-leaking radiator turned into a sprinkler!

Car is put back together enough for test driving around the neighborhood yesterday. Everything is looking pretty good so far. I'm going to do a few drive & flush cycles before I hook the heaters up and see what other junk comes out of the system. At least I can move it out of the shop so I can drain the water onto the driveway.