Honda BF75L cooling water issues

[Cpotts]

I've been away for a while but I started looking at the engine again....
I dropped the midsection/lower unit so I could insert an inspection camera up the exhaust. I was able to identify where the water is supposed to come out...it's only about 3 or 4 inches from the tip of the exhaust.
unfortunately the camera couldn't fit inside that hole so I couldn't observe any blockage.

I also used the camera to attempt to view the water passages in the head. It didn't quite fit there either but I was able to see one important thing - the downward pathway from the head to the exhaust. I could just barely see it. Not enough to see any type of blockage.

once again I used my air compressor to confirm that the blockage is at the exhaust water pathway.

I tried weed whacker line to try and snake it out from the bottom and the top. no luck.
Can I use something like a coat hanger? And does anyone know if there's a 1 way valve in that passage? I'd hate to use a hanger going the wrong direction if there's a valve.

 

[Cpotts]

 

[km1125]

There's no valve in that path, so you should be fine sticking something like a coathanger into that water passage. Remember though that the parts are aluminum, but any steel is going to scratch it up if you're being very aggressive at all. If you have some old windsheild wipers laying around, the little strips o stainless steel in them would be good for this purpose... they're a bit "springier" than a coat hanger and would flex more to get through the passages. Really curious to find out what's plugging that up.

 

[km1125]

View attachment 388227

That hole is where the BYPASS water gets into the exhaust from the water pump. It is NOT where water going through the head gets into the exhaust, which I believe is where your problem is. The smaller hole at the TOP of that picture should have a CLEAR path to the exhaust. Somewhere that's blocked.

 

[Cpotts]

That hole is where the BYPASS water gets into the exhaust from the water pump. It is NOT where water going through the head gets into the exhaust, which I believe is where your problem is. The smaller hole at the TOP of that picture should have a CLEAR path to the exhaust. Somewhere that's blocked.

bypass water goes to the exhaust?? I thought it all flowed to the telltale.
when you say smaller hole at the top, you mean the thermotat output hole right beside the tstat housing??

 

[km1125]

bypass water goes to the exhaust?? I thought it all flowed to the telltale.
when you say smaller hole at the top, you mean the thermotat output hole right beside the tstat housing??

I you look at the diagram back in post #33, you will see the "tiny hole". This is fed from the bypass hose, along with the telltale. So the bypass hose feeds both. It's just a small amount of water though.

Yes, that smaller hole at the top is the output from the thermostat and goes into the head. In the diagram I call this the "littler hole". After that water passes though the head, it goes into the exhaust. The bulk of the cooling water first flows from the pump into the block, then through the thermostat and into the head, then dumps into the exhaust. The bypass is a very small amount of water that just feeds the telltale, and also a little water into the exhaust (so the hot exhaust still gets cooled a little before the thermostat opens).

 

[Cpotts]

That hole is where the BYPASS water gets into the exhaust from the water pump. It is NOT where water going through the head gets into the exhaust, which I believe is where your problem is. The smaller hole at the TOP of that picture should have a CLEAR path to the exhaust. Somewhere that's blocked.

the hole I'm pointing to in the photo of the block/head isn't in the diagram. I think we surmised that it's a casting hole in post 56.when everything is assembled, the hole in question at the very bottom is blocked off. it's in that hole I used the camera to see the downward path to the exhaust

 

[Cpotts]

this is a video of the casting hole at the very bottom.. what I'm seeing is a) a water pathway coming in at the back ...presumably from the headsand b) a pathway going straight down to the exhaust. I'm guessing thats the major exit point to the exhaust. it lines up with the hole in the exhaust pipe I believe

 

[Cpotts]

Here's what it looks like going up the exhaust pipe. I with the camera could fit in that water hole. note the pinch weld inside the water escape hole. it the same weld you can see on the exterior pics of the exhaust pipe

 

[Cpotts]

@km1125 thanks for helping man! I appreciate it more than you know

 

[km1125]

the hole I'm pointing to in the photo of the block/head isn't in the diagram. I think we surmised that it's a casting hole in post 56.when everything is assembled, the hole in question at the very bottom is blocked off. it's in that hole I used the camera to see the downward path to the exhaust

Sorry for the confusion... you're correct! For the sake of conversation, from now on let's refer to that as the "casting hole" (whether or not that's why it's there). You could/should block that off... maybe by sticking a rubber cork in there and putting a big fender washer over that stud next to it and tightening a nut down on it. Then you could blow air or water into the exhaust and it should be forced "backwards" into the head and out the "littler hole" next to the thermostat.

I did not see any pics or videos in posts #68 or #69... perhaps they didn't upload properly?

 

[Cpotts]

Sorry for the confusion... you're correct! For the sake of conversation, from now on let's refer to that as the "casting hole" (whether or not that's why it's there). You could/should block that off... maybe by sticking a rubber cork in there and putting a big fender washer over that stud next to it and tightening a nut down on it. Then you could blow air or water into the exhaust and it should be forced "backwards" into the head and out the "littler hole" next to the thermostat.

I did not see any pics or videos in posts #68 or #69... perhaps they didn't upload properly?

click the text in those post...leads to YouTube vids from the inspection camera. or try these

 

[Cpotts]

had a little time today so I removed the powerhead. exhaust bolts are stripped so I can't get the exhaust off. .....argh!!!
I'm so close to solving this problem.

couple things:
oil pump looks good except the little bearing on the cover (first pic). what's the function of that singular ball bearing??

stripped bolts....any ideas regarding removal??

 

[km1125]

I'm not sure what bearing you're talking about, but could it be a "bearing" that's pressed into a drilled hole to seal the end of it after it was drilled?

I thought you had that exhaust off already (post #62)?

 

[MattFL]

Are the stripped exhaust bolts actually nuts on studs? If yes, use a nut splitter to remove them, if you can get one in there.

 

[Cpotts]

I'm not sure what bearing you're talking about, but could it be a "bearing" that's pressed into a drilled hole to seal the end of it after it was drilled?

I thought you had that exhaust off already (post #62)?

never had the exhaust off. Unused internet pics of a removed exhaust to help illustrate.

The oil pump cover has a weird looking single ball bearing . It might be a mute point however as it doesn't person directly to my issue. was just wondering what it was. You can see it better in this pic.

 

[Cpotts]

Are the stripped exhaust bolts actually nuts on studs? If yes, use a nut splitter to remove them, if you can get one in there.

stripped exhaust nuts were acorn style....they don't appear to be the originals. I finally got the appropriate nut extractor and was able to remove them

 

[Cpotts]

Used a good extractor to remove the acorn style nuts bolting the exhaust to the powerhead.
BINGO
The waterway down the exhaust was severely clogged. I had to use a screwdriver to scrape the packed on sediment out. There was lots of whitish hardened crud entirely closing the hole.

 

[flashback]

You found your problem! I'm happy for this .

 

[MattFL]

Great job finding the problem! When you get it back together, run some descaler through it to clean out the spaces you couldn't physically reach. Rydlyme works very good, Barnacle Buster seems similar. Just flush it really really good with fresh water after.