Coolant expansion tank filling up?

If this question has been answered, please point me in the right direction. Otherwise here goes.

 

My 2000 DRZ-400S coolant overflow/expansion tank was almost full when I bought it. The bike started over heating. Checked the radiator level and it had emptied itself (this is when I first bought the bike so I was unfamiliar with every bit of it). Flushed the system, put 50/50 standard mix in, got what air bubbles I could out, and replaced the cap with a new stock one. Everything seems fine except that darn tank is still filling up. I can put air pressure on the hose to push the fluid back into the radiator but it fills up the very next ride. 

 

Any ideas to why this is happening and what I can do to fix it?

 

Thanks

Does fan come on?

Have you bled system via LH radiator?

Have you tested fan switch?

Does fan come on?

Have you bled system via LH radiator?

Have you tested fan switch?

Fan does come on. I also installed a fan override switch from Ed at epic motosports. I bled from the top left screw but forgot to do lower one by engine.

The coolant overflow, or better ID'd as an expansion tank is a bit confusing but has been explained pretty well on a few threads. As coolant heats up it expands and goes into the tank. This is normal & how the system works. If the bike overheats, the tank gets full. As the engine cools, ALL the coolant should return to the radiators and the tank goes back to dry. If there is coolant remaining in the tank after the cool-down it means the coolant is low in the radiators & they need re-filling. Many have thought the tank is to be full or is a place to "top off" the system. Again, the tank is for expansion only and only holds fluid during coolant expansion. If coolant remains in the tank after multiple re-fills of the radiators and after cool-down.....you most likely have a leak in the system. I'll try to scan & post the simple but accurate explanation from the owners manual....page 53. Hope this helps.

Are you saying that the coolant level in the expansion tanks rises (when the engine heats up?), but then doesn't drop back down when the engine cools?

 

Do you see bubbles (boiling fluid) in the expansion tank when the engine is hot?  If the system is properly bleed and your HG isn't blown then I'd say the coolant cap is bad (isn't holding pressure in the system).

Can't seem to upload a pdf here??

Edited by TheMotoPros

I seem to recall a test of the coolant can determine if the head gasket is blown. This is down in the automotive world on a consistent basis. Same theory applies here

Could be a faulty radiator cap, not allowing the cooling radiators to draw the coolant back  from the overflow bottle. Really hope

this is the case, other options could get expensive.

you might want to also check the hose from the radiator to the catch tank.  If it has even a very small hole in it, the vaccuum created when the radiators cool off will be lost and the fluid in the catch tank will not return to the radiators -

Edited by steve_k

The coolant overflow, or better ID'd as an expansion tank is a bit confusing but has been explained pretty well on a few threads. As coolant heats up it expands and goes into the tank. This is normal & how the system works. If the bike overheats, the tank gets full. As the engine cools, ALL the coolant should return to the radiators and the tank goes back to dry. If there is coolant remaining in the tank after the cool-down it means the coolant is low in the radiators & they need re-filling. Many have thought the tank is to be full or is a place to "top off" the system. Again, the tank is for expansion only and only holds fluid during coolant expansion. If coolant remains in the tank after multiple re-fills of the radiators and after cool-down.....you most likely have a leak in the system. I'll try to scan & post the simple but accurate explanation from the owners manual....page 53. Hope this helps.

 

Just because there is coolant in the expansion tank when the engine is cool doesn't mean the system is faulty.  Myself and others fill the tank partially because it gives you an indicator of coolant levels in the system.  For example: coolant system is full and bled, engine is cool, level in expansion tank is 0.5" from the bottom, engine heats up, coolant level rises in tank to say 1.5" from bottom, engine cools, level goes back to 0.5" (all is good).  However if you notice the level drops below 0.5" then you probably have a leak somewhere or if the level stays above 0.5" then you also have a problem.  It’s easier to see in the tank, than have to open the radiator cap.

 

As long as the levels go up and down back to the same starting points then the system is working fine.

 

I seem to recall a test of the coolant can determine if the head gasket is blown. This is down in the automotive world on a consistent basis. Same theory applies here

Yes, you can either hook up a pressure tester to the radiator to monitor pressures, use a chemical test kit (tests for HCs in the coolant system) and/or visually see oil droplets in the coolant.

 

Could be a faulty radiator cap, not allowing the cooling radiators to draw the coolant back  from the overflow bottle. Really hope

this is the case, other options could get expensive.

 

You can test the cap with a pressure tester or just replace it since their relatively cheap. 

 

you might want to also check the hose from the radiator to the catch tank.  If it has even a very small hole in it, the vaccuum created when the radiators cool off will be lost and the fluid in the catch tank will not return to the radiators -

 

True, so the question to the OP is does the level in the tank keep getting higher each time to ride or did it just go up and stay up?

 

Just because there is coolant in the expansion tank when the engine is cool doesn't mean the system is faulty.  Myself and others fill the tank partially because it gives you an indicator of coolant levels in the system.  For example: coolant system is full and bled, engine is cool, level in expansion tank is 0.5" from the bottom, engine heats up, coolant level rises in tank to say 1.5" from bottom, engine cools, level goes back to 0.5" (all is good).  However if you notice the level drops below 0.5" then you probably have a leak somewhere or if the level stays above 0.5" then you also have a problem.  It’s easier to see in the tank, than have to open the radiator cap.

 

As long as the levels go up and down back to the same starting points then the system is working fine.

 

Yes, you can either hook up a pressure tester to the radiator to monitor pressures, use a chemical test kit (tests for HCs in the coolant system) and/or visually see oil droplets in the coolant.

 

 

You can test the cap with a pressure tester or just replace it since their relatively cheap. 

 

 

True, so the question to the OP is does the level in the tank keep getting higher each time to ride or did it just go up and stay up?

+1 on putting .5" of coolant in the tank when cool. I was just referring to the manual which maintains a "dry" tank after cool-down. The bit of extra coolant would keep the rads full for sure w/o removing the cap. I'm used to seeing mine dry when parked in the shop but I would say a bit of coolant at a certain level would be easier to see & measure in the tank. Just for further reference,  I'm riding an "E" & after two seasons have yet to re-fill the rads. However, I have looked down during a hot day & have seen that tank 1/3 or so full but then dry again after cooling. OP, as stated, it depends on what is actually happening in your case.

Liquid expands when heated much like air; the overflow tank is just there to accommodate a "full" system when running HOT (Because when your bike cools back down, it's going to suck that coolant back inside when it contracts).

 

Think of it like squeezing a juice box; the squeezing is the temperature, the straw is your overflow tank. So when you squeeze the juice box the liquid goes up the straw, and back down to the box when you let go.

The coolant overflow, or better ID'd as an expansion tank is a bit confusing but has been explained pretty well on a few threads. As coolant heats up it expands and goes into the tank. This is normal & how the system works. If the bike overheats, the tank gets full. As the engine cools, ALL the coolant should return to the radiators and the tank goes back to dry. If there is coolant remaining in the tank after the cool-down it means the coolant is low in the radiators & they need re-filling. Many have thought the tank is to be full or is a place to "top off" the system. Again, the tank is for expansion only and only holds fluid during coolant expansion. If coolant remains in the tank after multiple re-fills of the radiators and after cool-down.....you most likely have a leak in the system. I'll try to scan & post the simple but accurate explanation from the owners manual....page 53. Hope this helps.

Just went for an extended ride (plus its over 100F today). The bike was over heating towards the end. From what I've observed, I think the coolant is expanding into the overflow tank and then isn't returning and then emptying out the radiator as a result. Once the bike cools down I'll see how things look in the radiator and the hoses. When I changed the oil it looked normal, no smoke from the exhaust, and the coolant from before the flush looked good. So I'm going to guess it's a hose leak.

Just went for an extended ride (plus its over 100F today). The bike was over heating towards the end. From what I've observed, I think the coolant is expanding into the overflow tank and then isn't returning and then emptying out the radiator as a result. Once the bike cools down I'll see how things look in the radiator and the hoses. When I changed the oil it looked normal, no smoke from the exhaust, and the coolant from before the flush looked good. So I'm going to guess it's a hose leak.

A leak is most probable but usually is fairly visible after a ride. As steve_k stated, if the return hose is leaking that would release the pressure & not allow for flowing back to the rads. Check closely around the base of the H2o pump for brighter aluminum spots from leaks. A pressure tester would be in order for checking the whole system for sure.

Has anybody used clear tubing for the expansion tank line for a prolonged period of time?  I am ready to replace my line because it doesn't seem to be returning fluid properly anymore.

Steve

Has anybody used clear tubing for the expansion tank line for a prolonged period of time?  I am ready to replace my line because it doesn't seem to be returning fluid properly anymore.

Steve

 

I haven't tried the clear tubing - I went for the oem hose when mine started leaking - turned out to be a pinhole right up by the radiator cap

Edited by steve_k

Just went for an extended ride (plus its over 100F today). The bike was over heating towards the end. From what I've observed, I think the coolant is expanding into the overflow tank and then isn't returning and then emptying out the radiator as a result. Once the bike cools down I'll see how things look in the radiator and the hoses. When I changed the oil it looked normal, no smoke from the exhaust, and the coolant from before the flush looked good. So I'm going to guess it's a hose leak.

 

Stupid question, what makes you believe the engine is overheating?  Does the coolant temp light (red idiot) come on?  Is fluid boiling in the expansion tank?  Is fluid overflowing from expansion tank (onto the ground)?

Stupid question, what makes you believe the engine is overheating?  Does the coolant temp light (red idiot) come on?  Is fluid boiling in the expansion tank?  Is fluid overflowing from expansion tank (onto the ground)?

The red light does come on. The engine makes clanking noises and the head is becoming discolored. Its overheating.  I haven't had boiling fluid in the expansion tank in a while and I don't know if I'm losing fluid because I try not to sit still. I do know that to top off the radiator after the bike cooled down it took quite a bit of fluid. I replaced the hose from the radiator to the tank with some heavy radiator hose from oreilys. I'm going to see how it works later today.

Keep us posted mine is doing the same thing. Fills up coolant overflow tank after about an hour of hard riding. When it cools down the tank stays full. I rented a coolant pressure tester from orileys. Pumped it up to 30 psi did find it seeping at the top hose connection right radiator. Emptied tank filled radiators back up using bleeder screw took her for a ride and still filled up the coolant tank and did not suck it back after cool down. I ordered a 2.0 bar 30 psi cap, new radiator hoses and am eliminating the thermostat. Ill report back after I get it all and go for a ride. Forgot to mention I did the coolant pressure test again after I tightened up the leaky connection and didnt find another leak. No smoke out my exhaust or coolant in my oil. Hoping its a problem with the stock cap/radiator hoses or tstat

Keep us posted mine is doing the same thing. Fills up coolant overflow tank after about an hour of hard riding. When it cools down the tank stays full. I rented a coolant pressure tester from orileys. Pumped it up to 30 psi did find it seeping at the top hose connection right radiator. Emptied tank filled radiators back up using bleeder screw took her for a ride and still filled up the coolant tank and did not suck it back after cool down. I ordered a 2.0 bar 30 psi cap, new radiator hoses and am eliminating the thermostat. Ill report back after I get it all and go for a ride. Forgot to mention I did the coolant pressure test again after I tightened up the leaky connection and didnt find another leak. No smoke out my exhaust or coolant in my oil. Hoping its a problem with the stock cap/radiator hoses or tstat

I forgot about it but I did take my tstat out when I first serviced the system. It was stuck in the open position but I tossed it and made a gasket to replace it.

 

Today I found a small drip leak on the bottom of the water pump at the drain screw. So I put on gasket sealer and I'm letting it dry before I refill the radiator and test the system.

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