Linhai MP250A overheating and loosing fluid By jburd (Read 1,738 times)

[jburd]

I'm kind of stumped here so thought I would throw it out there to see if anyone has experienced the same thing. My 2007 Linhai MP250A is mysteriously overheating and I'm not sure why. I have had some issues with it in the past but have always figured it out. It looked like I had blown a hose so I took everything apart and replaced all of the hoses just to make sure. I refilled it with fluid and burped it. During that process, I discovered that when it was hot, fluid was pushing back to the reserve tank and out what looked to be an overflow spout on the back and top of the overflow tank. I just wrote it up as I had too much fluid in the overflow tank. I went ahead and finished the burping process successfully and the fan kicked on. I thought I was all set and put it back together. I took it out for a ride and I ended up blowing more fluid back up out the overflow tank and now the radiator system is low. Consequently the fan doesn't kick on like it should. I believe the thermostat is good since during the burping process it opened up to let the fluid flow. I changed the water pump about 2K miles ago. Does anyone have any other ideas?

[alleyoop]

JR is about the only one that can help you with the cooling problem. I am sure he will chime in once he sees your post.
Alleyoop

[jburd]

So here's the latest. I flushed the cooling system with a water and vinegar solution. When I first started flushing it, I left the radiator cap off to watch what it was doing. Whenever I revved the engine, the fluid would rise and backflow into the reservoir. I left the cap off and kept adding the water and vinegar solution. After awhile it started to flow better and I could rev the engine without it flowing backwards. Also the fan was kicking on and off which was a good thing to me. I completely drained the water and vinegar solution and replaced with coolant. I'm now working on the burping process. I have done it once and need to do it again. I'm hoping that I will have this corrected.
I am still a little concerned because I have read on other forums that a blown head gasket will cause the same symptoms. The flowing backwards is from pressure in the block leaking back into the coolant system. I checked the oil and don't see any evidences of water in the oil. I didn't see any oil per se in the coolant either so I'm not sure if I have the same problem or not. I did see some black specks (junk) in the coolant when I flushed it but was thinking that could have been build up that blocking the flow. It runs fine other than it has been running hot and back flowing into the reservoir. We shall see what happens when I finish burping it. If anyone has any other suggestions, let me know.

[jburd]

I went looking for the burping process that JR posted to make sure I was doing it right. Wasn't successful after the 3rd attempt. I actually stumbled on a couple other threads that indicated that I should see coolant flowing once the thermostat opens. I don't really ever see anything flowing per se. So I thought well maybe my thermostat is bad. I took it out and tested it in boiling water. It opens up. The only other thing I can think of is the water pump. I changed my about 2K miles ago but I guess there is always a possibility it is bad. What do you guys think? How do you know if your water pump is bad and should I actually see coolant flowing when I open the radiator cap? If anyone has any idea, I would greatly appreciate it. Has anyone had this kind of issue or is mine the only one?

[jburd]

So I have taken the water pump off and don't see any issues with it. The rod that drives the water pump appears to spin ok. I turned the engine over for about 6 seconds and it was spinning. I tried to turn it by hand thinking that maybe the shaft was spun off. It wouldn't turn by hand so I would assume all with that is as it should be. I have inspected the water pump and everything seems to be fine. I found my post from awhile ago when I changed the water pump and it doesn't seem to have the same symptoms as before. The impeller turns with the shaft going through the water pump. I'm not sure what else to look at. Any thoughts anyone?

[JR]

Ok when you pulled the impeller did you turn the engine over a bit to make sure the shaft that the impeller splines up to is turning?

The black specs, do you still have the fluid you drained that has those specs? If so and you can still see them take a spoon, paper towel or something that you might get a few of them out of the coolant and see if they are solid or oily like oil? If they are oil and you can still find them in this coolant that is not a good sign.

Also on the thermostat, sometimes they will open up partially and with the cap off will allow some flow. When you cap off the radiator and get the engine hot if it doesn't open up all the way then that can be a issue? They are cheap to buy and also you can do a test on one to see if it is any good?

Let me know about the black specks and we'll go from there.

JR

[jburd]

I have burped it about 5 or 6 times and I'm not getting anywhere. It still runs hot. The fan kicks on but when the temperature is about 3/4's. It's kind of random. It is acting like there is still air in the system. When I run it with the cap off, there are continuous bubbles of air that keep coming up. That still happens every time I burp it. At some point the air bubbles should stop unless it is indeed a head gasket and compression is backflowing through the system. I have removed the thermostat and tested it in boiling water and it opens all the way. The water pump looked good when I took it off and inspected it. The wierd thing is I haven't seen any black spots in the coolant which I would expect if the head gasket was blown. The black spots I saw before were in the reservoir so I am thinking they were just little pieces of rubber from the reservoir cap. I'm not sure what else to do. I have done everything that I know to do. Any other ideas?

[jburd]

JR, I went back to read your post on flushing the cooling system.

thescooterprofessor.proboards.com/index.cgi?board=cool&action=display&thread=24

I happened to notice the temp settings on the thermostat. When I boil tested mine, it never opened up until the water was boiling (over 200 deg F). The temp setting on your post was 176 deg F. I'm thinking my problem is the thermostat. I never see the coolant circulating so something is clearly blocking somewhere. I'm going to go ahead and replace the thermostat and see what happens. I'll keep you posted.

[JR]

I'd say you're on the right track and the thermostat is not opening all the way.

JR

[davec]

Have you run it without the thermostat?
(Like we used to on the old Fords that overheated.)

But, yea, that sounds like you're in the area

On mine, I can burp it, see the coolant circulating, temp light never goes above 3 of 6 bars.

But, still interested to learn of what the 'rest of the story' is.

Good luck

dave

[ellpee]

Different scooter, different everything probably, but my fan kicks in consistently at about the halfway point on the gauge, and keeps the needle there. Never seen it more than a needle-width above half, although I should confess I don't do much scooting in the brutal AZ summer heat. My fan still sucks juice like crazy from the charging system, but that's a whole different subject. Just throwing this in in case it helps somehow.

[jburd]

OK so I have removed the thermostat (I have ordered another one and am waiting for it to arrive) and am not any further along than before. I still do not see any circulating. In looking at the radiator connector, I am not sure where it would circulate from. Here's a link to one just to show you what I am referring to. .roketapartsdept.com/products/ROKETA_MC_54B_250_RADIATOR_CONNECTOR-18316-612.html" rel="nofollow" target="_blank">.roketapartsdept.com/products/ROKETA_MC_54B_250_RADIATOR_CONNECTOR-18316-612.html
The main hose (about 1" in diameter) going out the bottom of the cap goes to the top left of the radiator. There's another hose that goes to the overflow tank (about 1/2" in diameter). There is a small hose (about 1/4") that goes from the back of the connector to the top middle of the radiator. That is the only thing I could think would actually flow. I saw some air bubbles come out of that but that was pretty much it. I got one of those oil siphon pumps you use to drain oil from a lawn mower and hooked it up to it and pumped some fluid out just to make sure nothing was clogging that line. I did get some hard black chunks come through that hose. I just replaced all the hoses connected to the radiator except for the one coming out of the bottom of the radiator going to the water pump. I replaced that one about a year ago. Does anyone have any ideas where to go from here?

[jburd]

I'm wondering if the radiator is plugged. When I replaced the hoses, I remember seeing some white "ish" sludge in the radiator opening. I cleaned it off really good and put the new hose on. Is there a good cleaner that I can use? I tried vinegar and thought it worked but it didn't seem to solve my problem. I could always try it again for a little longer. Any thoughts anyone?

[ellpee]

Not same as my scoot, but there MUST be a second, largish hose coming out the bottom of the radiator. On mine, that hose runs to the water pump, and is minimally visible on the lower right side even without pulling any plastic. Coolant circulates out the bottom, through the water pump, through the engine, out the top (if the thermostat has opened), and through the upper large hose back to the radiator. When heat/pressure reaches a certain point, the radiator cap allows excess fluid to flow into the overflow tank via the smaller tube. The REALLY small tube, not sure what that's for.

[jburd]

That small hose coming from the top of the radiator is the only logical thing that would possibly circulate when I open the radiator cap. When looking at the radiator from behind, there is 1 large hose in the upper left (goes to the radiator cap connector), 1 large hose in the upper right (goes to the thermostat housing on the engine block), 1 large hose in the lower right (goes to the water pump), and the really small hose coming out of the top middle of the radiator (goes to the back of the radiator cap connector). That small hose seems to be the only possible place to see coolant circulating from. I still can't understand how there would be fluid circulating. I'm baffled.