Gettin out that 27 year old coolant... help?
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Okay so I bought a 1985 vn700 for 200 bucks that needed work... then bought another 85 vn700 for 500 bucks. The more expensive one is the one I have on the road, for obvious reasons. Anyways, it's only just barely been broken in. 5k miles was reassuring, BUT it was all stock, like, everything. It had just been sitting. Just replaced the stock tires on it, but I have this overheating issue that stems from old nasty coolant that wasn't circulated for decades.
Initially, I drained it all and ran a garden hose through it to get the crud out of the engine and radiator. After replacing with water, it still was barely better. I then removed the thermostat from my system because it was simply overheating too quickly to ride for longer than about 5 minutes still.
After numerous heating/cooling cycles I flushed again... rinse repeat about 10 times. After still no luck, I was thinking of using something other than water to flush it, after all, I had been getting small brownish-black flakes of gunk from the system. Less and less from each successive flush, but was certainly cause for concern. All of the coolant flush chemicals on the market are too weak or intended to clean oil from the coolant, which was not my problem. I have built up solid coolant or some such on the inside... hence the blackish gunky flakes. This called for something more powerful.
Hydrochloric acid! Diluted of course, and circulated while the bike was running for about 3 or 4 minutes, then drained and rinsed. LOTS more gunk came out after the water flushes had started coming out clean.
The bike became driveable for long distances! Only barely, however. It is able to run with the temp needle hovering over the center of the icon, but only at 50+ mph at low rpms... start driving more spirited or slow down for stop-and-go city driving and it gets mighty close to the red. Fan seems to work, and it appears to be the only thing keeping it from touching the red. Although, sometimes when it's hot I can hear the coolant in the reservoir boiling, which is NOT OKAY! I have driving the bike about 600 miles or so in this condition.
I recently downloaded the manual and found out about three additional drain plugs for the coolant, one at the bottom of each cylinder and one on the bottom of the crank case. I took these all out and tested the flow with my garden hose. I got fantastic flow from the bottom, and decent flow from the front cylinder, but nothing was coming from the rear. I then fitted the garden hose directly to a hose with a clamp to pressure test it. The pressure from the garden hose was enough to leak past some tight hose clamps, so it must have been far greater than anything the system would normally experience (pressure cap was where I fitted the hose, so it was removed at the time). Even under this pressure, I was only able to make the rear cylinder drain plug dribble slightly. To put it in perspective, the water that came out amounted to nothing more than a few milliliters.
This leads me to believe that my rear cylinder has extremely reduced coolant flow and is thus getting hotter than the front cylinder, which is also bad news.
Now, I was wondering if shoving something into that drain plug hole might be a good idea. I wanted to try and break some of that **** up so I get more flow, since I'm planning on flushing with another diluted hydrochloric solution. The difference between no flow, and some flow could mean a world of difference when flushing the whole system at once.
Also, I had an idea to use a hose fitting to pump my hydrochloric solution directly into the rear cylinder drain plug. Straight to the source of the problem you know? I could also avoid any more unnecessary wear to the cooling system by flushing the entire thing with the acid solution.
Also, other discrepancies I have already sorted out:
- Water pump works, it is circulating with good flow (I just don't know if it's all going through the front cylinder)
- Radiator is not clogged and appears to have good flow.
- Nothing is leaking unless you count coolant (water) boiling and flowing out of the reservoir overflow.
- I thought air in the system might be an issue, since I have never used the bleeder valve, but finding no flow in the rear cylinder makes me think that's the sole cause... or at least the major one.
- The fan acts strange; doesn't always turn on when the engine is hot and the bike isn't moving (works predictably most of the time)... also waits about 20 seconds to turn on after the bike is shut off, then runs for 10 seconds, then shuts off for good.
TL;DR: Old bike, original coolant, **** gummed up inside my rear cylinder and my drain plug on that cylinder has nearly no flow.
What do you guys think? Any input here? Questions perhaps?
Any input is appreciated!