2001 SXR 700 losing coolant

Rebmo

Rebmo

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Jan 11, 2014
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Rural SE Wisconsin
I have a problem with my 2001 SXR 700 (3k mi, very clean and good condition, studs with good clearance)losing coolant. I've had the sled for 2 years now and this is the first year we had enough snow locally to really use it. I made 2 runs with it 1) 48 miles in mid teen temps with plenty of snow on the trails 2) 38 miles mid 20s temp and plenty of drifted snow on 75% of the trails. After run #1 the overflow tank was empty and I refilled with coolant. The temp light never came on during the run and performance was very good. I ran with 4 other sleds at a pretty aggressive pace. After run #2 I noticed the coolant level in the overflow was down near the bottom again. I also did not have the temp light come on and the sled performed great.

So I googled this issue and found several potential problems. First I checked for coolant leaks and did not find any. There was no evidence of coolant leaking out after I refilled for the 3rd time. I ran the engine at idle (varying the speed) for about 10-15 minutes and did not notice any coolant loss. I'm not sure how much "smoke" should be in the exhaust after warm, but there did appear to be some whiteish smoke (may be normal for a 2 stroke after warm, maybe not?), after the engine warmed and choke was completely off. I did use the coolant recirculation around the carbs to keep them warm both times I ran.

My background with engines is fairly deep. I have done rebuilds on tractors, car engine top ends, cycles, and have a pretty decent tool assortment, including torque wrenches, air tools, compression tester, etc.. I don't have a coolant pressure tester. On the other hand, I'm a garage mechanic, not a everyday pro, and have no experience with snowmobiles. This is my first snow machine. Rode a few over the years, enjoying this one but need to solve this issue.

That said looking for where to start. I have read about bad head gaskets. But those with head gasket coolant leaks seemed to have overheating issues. I have read about bad water pumps, but again most have overheating issues. I have not had overheating issues (no temp light coming on).
The temp light does come on when I fire up the sled in the initial start check mode so I'm assuming it works. I can't be sure the sensor is working.

So where to start? Pull the plugs and look for a shiny one? Is it likely my leak is very small and not overheating since there is barely enough coolant to keep it from overheating? It's possible there is a coolant system leak that doesn't actually happen until I ride it hard and pressurize the system. Is there a coolant pressure check system anyone can recommend that I can use to check this system (small cap? size?)

Looking for a logical approach to figuring this out and unfortunately the more I read the less certain I become of where to start. Any experienced advice would be greatly appreciated.

TIA Reb
 
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Well I have learned much of this subject in the past few months here. Read my thread here with very useful info: http://www.totallyamaha.net/forums/showthread.php?94216-SX-700-Engine-issue

1) First you can bleed the coolant system. Take the seat off and the bleeder is over the rearmost heat exchanger. One bolt. Lift the rear of the sled and see if air/bubbles are released.

2) You can pull all the plugs and look at the top of each piston. All should look darkish and dry. If any are (washed) clean looking you can know theres been coolant in that cylinder. (bad head gasket)

3) Pull the head and look at each of the three head gaskets for cracks and damage

4) Pull the entire exhaust and get at the water pump cover. Pull that out and check the impeller.

5) Lastly there is a brass gear on the crank which turns this impellar^ Can go bad.
 
More than a few guys would keep riding it (being as its not overheating) and keep a closer eye on it. With sled running you can take to coolant cap off and verify flow. Phantom leaks have ben found threw out cooling system. Could be a pin hole head gasket, water pump issue, pin hole in an exchanger or even a leak in one of the hose to exchanger locations. Each time you stop for a break go over sled, sometimes its a not even a complete drop to drip that will indicate where the leak is. It may be in a location that wont leak sitting or even running up to 4-5k rpm, it may need the 6+k rpm of actually riding it to leak (more rpm = more pressure). I would considering bringing some antifreeze with you if needed on the trail (1 liter soda bottle in the glove box better than nothing)
 
Thanks for the replies. I did order a MityVac motorcycle cooling system test KIT Model MV4510DIBD which I hope will fit based on the description. I found it for $30 plus $11 shipping so not too bad (if it fits). Hopefully I can pressure test the sytem at full operating cap pressure and hopefully find the elusive leak source. Otherwise I may have to get the wallet out and head to the dealer. I may run it again if we get so lucky to have some decent snow again and like the idea of keeping spare bottle of antifreeze on board and checking often.

Thanks for the ideas, I'll post back as I work through this.

Reb
 
I recieved the MityVac coolant pressure tester and checked out the cap & cooling system and it holds pressure with no visibable leaks when static testing. I shut down tonight, but tomorrow I'm going to bleed/check the cooling system in case there is a bubble in the system causing a problem. Also, I'll run a dynamic pressure test and see if I have a leaky head gasket or block. I did leave 14 psi on the cooling system and I'll see how it holds overnight, and if any coolant puddles form under the sled. So far not even a drop after an hour and inspected the hose connections, heat exchangers, and also the water pump area. No Leaks.

I started looking ahead in case I need a head gaskets (3) and found 2 P/Ns on several sites without any description on the difference or application? Any advice on the proper head gasket for my sled (if needed)?

Here's the 2 listed Head gaskets, I'm not sure which one for my sled??
5Gasket, Cylinder Head 1 (8CH5)8CH-11181-01-00$29.92 qty 3
5Gasket, Cylinder Head 1 (8EA3)8DG-11181-00-00$39.41 qty 3

TIA for any advice,

Reb
 
GASKET,CYL HEAD 1 (8CH5)
8CH-11181-01-00 3 $40.99 $34.43

GASKET, CYLINDER HEA (8EA3)
8DG-11181-00-00 3 $53.99 $45.35


Copied and pasted from Port Yamaha...same ones you already had. No idea which you need or what the difference is.

Looking at the parts fische they list two different heads as well. No idea what the difference there is either but that's probably the difference.
 
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8CH... (8CH5) = 700cc
8DG... (8EA3) = 600cc

Yamaha often covers multiple similar sled models by referencing the same diagram and parts list, even though the title shown on the page you pull up is for only one model. If you pull up the similar model (in this case 2001 SXR 600), you'll get the same diagram and parts list and the title will show the 600cc version.
 
Thanks for the replies:

Looks like I would need the 8CH5 for my SXR 700.

Today I hooked up the coolant system pressure tester and pumped up the coolant system pressure to 14psi and bled the rear heat exchanger via the back screw under the seat. Hard to tell but it seemed like a little bubbling at first but not much. I locked it down and added a tiny bit of coolant and repeated and it seemed to not have any air bubbles in the system. I then pressure checked at 14psi and it held solid. I then proceeded to do a "dynamic" pressure test. I released all pressure generated by the tester and started the engine. There was no immediate pressure gain (which the tester manual says would indicate a blown head gasket. Then, with the engine running I pumped up the pressure to 14psi (system pressure) and observed the needle. The needle vibrated +/- a half psi. The manual says if the needle vibrates it could be a cracked block or head?

So the needle did vibrate, but only a bit, is that normal or should the coolant sys press tester needle be steady when the engine runs? Unfortunately the manual does not clarify how much vibratiion. I would think the water pump and water movement would add some vibration to the "pressure indicating needle".

So in summary so far, the coolant sytem has been bled per the Yamaha shop manual. The static pressure test does not indicate any leaks (no pressure loss @14psi). The dynamic pressure test did not indicate a blown head gasket (no immediate pressure build up on gauge at cold start). The pressure indicator needle does vibrate slightly +/- .5 psi with engine running and pumped up to 14psi (not sure if this is normal or indicates problem).

I did activate the carb warming valve and noticed a coolant leak at the top of the on/off valve when moving back & forth? This does not seem right. Does this sound like the problem? It only seems to leak out the top when I move it between on & off? I see some evidence of leakage around it but not the est 8-12oz I'm losing when riding?

Notes: I'm losing 8-12oz of coolant on 40-50 mile rides. The engine runs fine. NO overheating light is coming on. No indications of leakage around hose connection and water pump area, except the on/off carb heat valve when moved.

Any inputs on the on/off valve or clarification on if any vibration on the pressure tester needle is normal when running would be appreciated.

Reb
 
Could be that on/off valve and the coolant is gone by the time you stop to look at it. If its the only place showing a leak. Swap it out and go from there. Keep in mind when aluminum heats up it expands as well. Might be worth while to pressure test it with everything at operating temp. Personally I would keep riding and keep an eye on it.
 
Thanks, DA,

I ordered the OEM On/Off valve. That should not be leaking in any case so I'll fix that and keep monitoring things with spare coolant on board. I also checked the cooling system fill cap and it releases pressure at anything above 14psi (spec) and drops back to 14psi. So that checks out. Since it's not overheating I suspect the on/off valve could be the culprit. Any harm in pulling it and just putting a bypass in, thus leaving it on all the time? I don't see it warming up soon round here, so it would only be a week or so until the new valve arrives.
 
OK, I think this problem is solved. I went for a 69 mile run last night (had a blast) and did not lose a drop of anti freeze/coolant. I had 2 soda bottles of Anti-freeze mix (just in case but didn't need) and stopped a few times and checked the overflow bottle level and it did not change from the full/hot line.

So here's the things I did, and one solved it, but not sure which one solved the coolant loss problem, yet it could have been 2 or 3 combined issues?

1) I bled the coolant system using the Mityvac coolant sytem tester to create 14psi coolant system pressure, then bled the rear heat exchanger using the rear screw (seat removed by removing 2 nuts in back storage, 2 snaps either side front, and flex cord over 2 screws very front). Some foamy antifreeze came out at first on round 1. After bleeding a bit, I tightened and refilled maybe 2oz of coolant. Then I repeated and had solid coolant flow out the bleeder. I tightened the bleeder bolt, and added maybe another 1/2 oz coolant, then capped off the coolant sysetm

2) I pressure tested the coolant fill cap. Before testing I scrubbed it down with some soap & water since it had some dirt on top and wanted it to be clean. I tried to check it 3-4 times since the seal did not seat and air was leaking when I pumped the tester. I then recleaned the rubber under warm running water. I tried the cap test again and it worked perfectly. I pumped it to 16psi and it leaked until it dropped to exactly 14psi and then it held rock solid. One take away is that you really need to make sure the cap & seal are super clean, plus be sure it seated evenly to get a good seal. After I cleaned it thouroghly, it sealed up to the tester every time. So if it was leaking on the sled, it may have overflowed at very low pressure and dumped out excess coolant through the overflow bottle.

3) When I was pressure testing the system I did not notice any leakage throughout the coolant system during a thourough inspection. Later when I had the system under pressure I happened to move the carb heater lever from OFF to ON position. As I did this coolant leaked out the top of the on/off valve. When the coolant system had been losing coolant I had the valve in the ON position both times. So it's quite possible the carb heater in ON position was leaking slowly and causing the coolant loss. Never the less, it leaks, and I use it in cold weather. I did order a new OEM ON/Off valve for the carb heater ($14.95 including shipping Ebay NOS). In the mean time I have the valve in the off postion and it is not leaking. I also noticed that there was some evidence of dried anti-freeze below the valve indicating it had been leaking.

So there you have it, one of the 3 items above was the source of my coolant loss. Experts may know which one better than I, but I did find each of these 3 possible causes in my google searches and checked them all and found issues. At this point I'm not pursuing a head gasket replacement since the leakage is no longer happening and that would be fixing something that's not broken.

Thanks for all the ideas, and happy sledding,

Give me a shout if you are having this problem and need clarification on any of the above.

Over, Reb
 
The on/off carb heater valve is now installed and does not leak like the one I replaced. I do like to run the carb heater and curious regarding anyone else's preference regarding using/not using the carb heater. To me it seems like a no brainer to heat the carbs in sub-zero weather. Any inputs?

Thanks, Reb
 
I always run with my carb heaters ON. However, I came upon your post because my 2000 SX-R 700 is mysteriously losing coolant now too. I'm going to check the things you did here and see if one/all of them are my problem as well. Thanks for the thorough post!
 
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