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Birdy426

Coolant Recovery Problem

14 posts in this topic

Here's the problem...I have an 01 WR426 (it has a 444 big bore kit a Boyesen Water Pump housing and impeller, and some other mods that aren't really relevant to the problem I'm having).

When I ride, coolant expands and flows out of the radiators like it should, and accumulates in the catch tank. So far so good. As the bike cools, it should siphon the coolant back into the rads. The operative word there is "should". It doesn't. After a ride, the catch tank is full, and the radiators are down several ounces of coolant. I drain from the catch tank and refill the rads, only to repeat the next ride. I am running "Coolanol" with water wetter mixed per the instructions.

At first, I thought the overflow line might be pinched or kinked. I took a look, and no, it's not. I had put a slip fit barbed union in each line to allow me to disconnect the lines and remove the subframe without draining the coolant. I thought one of those might be leaking vacuum on cool down, so I replaced the hoses and did not splice them. Still no joy. Only other thing I can think of is to replace the radiator cap. Am I missing something?

Any help or experience is appreciated.

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Rad cap sounds like the next place to go. You're not seeing any leaks in the radiator itself, right?

Steve

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Rad cap sounds like the next place to go. You're not seeing any leaks in the radiator itself, right?

Steve

Nope...no apparent leaks from the rads, from the overflow tubes, nor from the water pump. The coolant is being pushed back up into the recovery tank...just not geeting drawn back into the radiators.

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It sounds like you are loosing the vacuum that draws the coolant back into the system. Is the cap on the recovery bottle tight, is it cracked, and is the gasket inside the cap in place/tact? The only other ting I can think of is that there is some sediment or something blocking the passage at the bottom of the tank. Check the upper hose to the bottle for leaks as well. Keep us posted.

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Radiator cap is the first pssible culprit, patyially clogged vent from the recovery tank also a possibility.

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Radiator cap is the first pssible culprit, patyially clogged vent from the recovery tank also a possibility.

I'd second the rad cap or the clogged overflow vent. I don't think the overflow cap should affect things, since the overflow bottle is vented at a seperate location (not at the overflow cap like on the radiator). When you open the radiator cap after the bike cools down, is there a little pop from the suction in the rads - ie - is there vacum in the system? Have you installed a new rad cap or a higher psi cap? I'm wondering if a higher psi cap may not release enough to let the coolant back into the rads. The pressure of the expanding coolant is probably a much stronger force than the vacuum created when the coolant cools.

This would also back up the clogged overflow vent. Pressure would probably force air or coolant out of the overflow bottle even if there was a slight clog, but vacum may not be strong enough to overcome it.

My carb and coolant vent hoses clog daily with ice so I'm always checking them. I've never experienced the problem you have, but coolant boiling over and draining out of the vent would melt any ice in the line, so it would be free when the engine cooled.

In this pic you can see my lines are plugged

ventice.jpg

and in this one you can see that the coolant overflow line tends to free itself automatically.

ventice1.jpg

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OK, found the problem...and boy was it one of those ont he fringe things. I took off the L/H side panel, took off the coolant recovery tank, drained out he coolant thru some cheesecloth to check for boogers in it, then checked the tank for clogs and such in the inlet and vent. Nothing. Put the tank back on, filled it to the full mark, marked the level with some speed tape, checked the coolant int he radiator, started the bike and watched as it warmed up. Coolant pissed into the recovery tank. Good. When the bike was cool, I cheched the level int he tank. Right back at the mark. Checked the radiators. Full. Hmmmm. Put the side plate back on and went for a ride. Came back, and when the bike cooled off, you guessed it, the coolant tank was overfull, and the radiator was low. Took the side panel off, and found that I had not trimmed the plastic reenforcement web enough (they are aftermarket side panels that can be used either on YZFs or WRs...you cut at the molded in lines) and it was pinching the lines against the frame. The pressure from the radiator was enough to push the coolant out, but the vacuum on cooldown wasn't enough to pull it back. Whoda thunk?

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OK, found the problem...and boy was it one of those ont he fringe things. I took off the L/H side panel, took off the coolant recovery tank, drained out he coolant thru some cheesecloth to check for boogers in it, then checked the tank for clogs and such in the inlet and vent. Nothing. Put the tank back on, filled it to the full mark, marked the level with some speed tape, checked the coolant int he radiator, started the bike and watched as it warmed up. Coolant pissed into the recovery tank. Good. When the bike was cool, I cheched the level int he tank. Right back at the mark. Checked the radiators. Full. Hmmmm. Put the side plate back on and went for a ride. Came back, and when the bike cooled off, you guessed it, the coolant tank was overfull, and the radiator was low. Took the side panel off, and found that I had not trimmed the plastic reenforcement web enough (they are aftermarket side panels that can be used either on YZFs or WRs...you cut at the molded in lines) and it was pinching the lines against the frame. The pressure from the radiator was enough to push the coolant out, but the vacuum on cooldown wasn't enough to pull it back. Whoda thunk?

Good work tracking down the source Birdy, and I especially liked the boogers catcher comment. :thumbsup: :thumbsup:

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Good work tracking down the source Birdy,

Really just dumb luck...had I put the side cover back on before I started the bike and let it idle in the garage, I'd still be pulling my hair out trying to figure out what was happeneing...

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OK...still tango uniform...here's what I've done so far:

New radiator cap

replaced all hoses

drained and flushed the system

No Joy.

Replaced new radiator cap with the cap from my son's 250 that works just fine. No Joy

Took the catch tank cap off to be sure the catch tank wasn't vapor locking.

No Joy.

No kinks in the hoses, good radiator cap, still nothing. Plugged up the end of the vent hose, clamped a schrader valve in the hose from the radiatoe (with it disconnected from the radiator, of course) and pressurized the catchtank and hoses to 3 psi and monitored for leaks. No leaks.

Anyone have any ideas?

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Picked up a new OEM radiator cap and hoses, and put them on. Still no joy. Pumps coolant into the recovery bottle but doesn't draw it back into the rads. I teed a combination vacuum/pressure gage into the overflow line, and ran the bike for a while. After about a minute, the cap started to vent, and there was about 1 1/4 psig in the line. Pretty normal, I think. On cool down, however, there was no vacuum, ever. I was expecting at least 6-8 inches of water, as that's the differential between the coolant tank inlet and the radiator inlet...Any suggestions?

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I posted on your other thread but here's an idea.

Pull the line that goes to the coolant overflow tank at the tank end and run it into a catch pan or bucket. Start the bike and let it purge off the expanding fluid. After it has completed the warm up purge hook up your vacuum gauge and shut it down. If you don't get vacuum there is a problem in the cooling system allowing air to enter.

If you do get vacuum then dump the recovered coolant back into the radiator and put the hose back in your catch pan so that it's near the bottom. Start the bike and let it do it's thing. Shut it off and keep the end of the hose below the level in the catch pan. It should suck it back into the radiators. If it does then your problem is still somewhere between the radiator and the overflow tank.

Post your findings.

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Finally figured this out...Blown head gasket. I realized that the bike would recover all of the coolant that it bioled off if it was just sitting in the garage. When I took it out and wicked up the throttle, it would "boil off" coolant even before the bike had a chance to get hot. I was pushing more coolant out of the rads than they could recover. Pulled the head, and sure enough, a leak between the cylinder and a water jacket! Replaced the head gasket, and rode about 80 miles today with no issues...

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