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Exhaust gasses pushing coolant out

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Hello all. Long time reader. First post here.

I have a 2006 drz400sm. It's got 10k miles on it and the previous owners hacked it up a bit. Safari tank and no shrouds because they cut the tabs off the radiators to clean them up. Removed fan and horn and front signals. Cut plastics a bit and a few other things I'm forgetting. Anyways it was a good deal so I couldn't pass it up.

Last week when I was riding in stop and go traffic in 85* heat the coolant boiled out of the overflow and onto the ground. I shut the bike off and let it cool. Put some water in it and drove it home. When I got back I drained the water and replaced it with engine ice. I noticed a lot of tiny bubbles coming into the catch and that it would dump on the ground in about two minutes. I did a search on here and the conclusion was the head gasket for similar problems. I have since removed it and taken many pictures but can't tell where it went bad. If I post some pictures would any of you be able to confirm that I have taken the right step here and diagnosed the correct problem?

And yes I did check all connections for the cooling system as well as the function of the water pump and bled the system properly before I decided to remove the head.

Thanks for reading.

Sparks

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No oil in water. No water in oil. Just lots of gasses coming through the radiators pushing the coolant out before it gets hot. Takes less than three minutes before it really starts bubbling out and ends up on the ground.

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Did it smoke? Did you try running it without the rad cap on and looking for bubbles? Obviously too late for that now but I mean before you pulled the head. It doesn't really look like it was leaking from the pics, I don't know what else to tell you unfortunately. Hopefully another member chimes in with more helpful info

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Could've been just a bad radiator cap... my other bike began spewing coolant out the overflow. Tested the cap, it was bad (didn't hold enough pressure), replaced it and the bike has been good since.

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I ran the bike without the rad cap and could see coolant moving as well as the various sizes of bubbles coming out. Looked like boiling water after about two minutes. Ir heat gun showed radiators reaching no higher than 180*. Cylinder head at exhaust port was showing 220* after shut down. I shut it off immediately after the coolant came up past the filler neck on the right side. This all happened in about two minutes. Pulled cap, watched for coolant flow, watched as coolant appeared to boil out, used the ir heat gun to monitor temps and coolant never reached 200*. After shut down the system would pull what was left in the overflow back into the radiators. Before removing the head I ran it to see if it was just me getting it too hot. I came back to the house and let it idle. It was dumping coolant out just sitting there immediately after parking it. Temps showed rads at 190* closest to the engine. Coolant still dumped out and I shut it off before there was nothing left in there. Had to refill rads because they were about dry. There was no smoke coming out of the exhaust or any loss of power.

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I ran the bike without the rad cap and could see coolant moving as well as the various sizes of bubbles coming out. Looked like boiling water after about two minutes. Ir heat gun showed radiators reaching no higher than 180*. Cylinder head at exhaust port was showing 220* after shut down. I shut it off immediately after the coolant came up past the filler neck on the right side. This all happened in about two minutes. Pulled cap, watched for coolant flow, watched as coolant appeared to boil out, used the ir heat gun to monitor temps and coolant never reached 200*. After shut down the system would pull what was left in the overflow back into the radiators. Before removing the head I ran it to see if it was just me getting it too hot. I came back to the house and let it idle. It was dumping coolant out just sitting there immediately after parking it. Temps showed rads at 190* closest to the engine. Coolant still dumped out and I shut it off before there was nothing left in there. Had to refill rads because they were about dry. There was no smoke coming out of the exhaust or any loss of power.

 

 

your water pump died would be my guess. 

 

water pump died = coolant boils, or has air trapped somewhere (left radiator my bet) and that builds pressure leading to the bubbles that eventually burp into the over flow, then the ground. 

 

this is supported by the hard-to-find-damage head gasket you've checked. 

 

i seriously doubt it's a cracked engine case anywhere. that usually shows up as lots of bubbles everywhere. 

 

 

 

 

you did mention that there was not any -flow- at the radiator cap, right ? 

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There was plenty of flow at the radiator cap. Could see the coolant rushing past the opening.

 

 

 

well, shot me full of holes then. ;-)

 

ok, if you've replaced the headgasket and it's still happening, i'd look to bleeding air off the LEFT radiator via that small bleed valve at the top. that's the only reason i can see for boiling, unless on of the radiators is partially blocked. 

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I am waiting for the gasket to arrive. Should be here in about an hour. I am familiar with the coolant bleeding procedure. There are two bleed screws and I use both as well as a lot of shaking and a quick turn over to get those remaining bubbles out of the system.

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Pressure testing the cooling system would have been a good idea.

Testing the air in the coolant expansion tank for presence of exhaust gasses would have been a good idea.

 

"Seeing" a head gasket leak by looking at the used head and gasket is iffy at best.

 

Sometimes you'll see a very clean spot on the head ("steam cleaned by leaking coolant"

Sometimes you'll see a clear track where coolant has been pushing past the gasket.

 

BUT when you have no coolant transfer, and the gasket is just leaking exhaust pressure from the combustion chamber . you may not "see" a head gasket leak by visual inspection.

 

 Check the head and cylinder for flatness (they will be fine, but check) install a new gasket. Tq head bolts to 43 ftlb.

Replace radiator cap.

Pressure test the cooling system.

 

Go ride

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Checked the surfaces with a straight edge. Still flat. Waiting on the gasket to arrive. I will post again after assembly. Thanks everyone for the help.

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Pressure testing the cooling system would have been a good idea.

Testing the air in the coolant expansion tank for presence of exhaust gasses would have been a good idea.

 

"Seeing" a head gasket leak by looking at the used head and gasket is iffy at best.

 

Sometimes you'll see a very clean spot on the head ("steam cleaned by leaking coolant"

Sometimes you'll see a clear track where coolant has been pushing past the gasket.

 

BUT when you have no coolant transfer, and the gasket is just leaking exhaust pressure from the combustion chamber . you may not "see" a head gasket leak by visual inspection.

 

 Check the head and cylinder for flatness (they will be fine, but check) install a new gasket. Tq head bolts to 43 ftlb.

Replace radiator cap.

Pressure test the cooling system.

 

Go ride

+1.

 

To me it doesn't really sound like a typical head gasket leak if it takes 2 minutes to start blowing out the overflow. That sounds like typical overheating without any sort of radiator fan to cool it down. Normally if a head gasket is pressurizing the system then it does it as soon as the engine starts.

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Pressure testing the cooling system would have been a good idea.

Testing the air in the coolant expansion tank for presence of exhaust gasses would have been a good idea.

 

"Seeing" a head gasket leak by looking at the used head and gasket is iffy at best.

 

Sometimes you'll see a very clean spot on the head ("steam cleaned by leaking coolant"

Sometimes you'll see a clear track where coolant has been pushing past the gasket.

 

BUT when you have no coolant transfer, and the gasket is just leaking exhaust pressure from the combustion chamber . you may not "see" a head gasket leak by visual inspection.

 

 Check the head and cylinder for flatness (they will be fine, but check) install a new gasket. Tq head bolts to 43 ftlb.

Replace radiator cap.

Pressure test the cooling system.

 

Go ride

Seems like a Marquez sticky on this subject might be in order as this topic pops up every couple of weeks.

 

Some of the rider suggestions don't make any sense others do but it usually takes the  OP a bit of time before he does the enevitable pulling of the head.

 

I've mentioned my experiences with coolant leaks on the exhaust side in both my DRZ's and GasGas's.  I've never had a water pump failure but I have had a thermostat failure which in turn caused a head leak failure. Both of these are easy to check. If water is flowing thru the motor as can be observed by looking through the opened radiator cap hole while the motor is running than neither of these is the problem.

 

The assumption that the gasket failed has not been the case in all my coolant leaking problem. As often as not, head warpage and gasket failure were the final factors. In one case with my 95mm stock bored GG the head gasket was still good but both the head and barrel were warped. That's  why a DRZ bore of 95mm is not recomended.

 

As Marquez notes, and he seems to very experienced with this issue. It's time to replace the gasket but also check  the barrel and head for warpage. As I don't have a surface grinder, and warpage is the problem I just hand sand them useing #80 sandpaper glued to a 10"x4" pressed board. This has always worked for me so far and with this method you don't have to pull the valves.

 

I'm not an expert by any means but in my limited experience, I have always found exhaust pushing the water out to be a failure caused by an over heated motor and because the exhaust generates the heat, the problem will be found around the exhaust side of the head and usually just above the exhaust port.

 

As an aside. I had one unusual DRZ water pushing out problem where the head bolt next to the exhaust port was just finger tight. The gasket was still good and so was the barrel but the head just above the exhaust port was really warped. This was caused by a thermostat failure and with no water flowing thru the head the area.... that's where the failure occured.

 

Tony

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I have checked the surfaces with a straight edge and found no high spots or low. The engine did overheat and boil my coolant out before the above mentioned symptoms. I have removed the radiator cap and witnessed flow through the radiators followed by a multitude of bubbles. As soon as there was flow the bubbles started and pushed coolant out of the radiator. Replacing the cap after a cool down and starting the motor again resulted in the same symptoms. Very quickly there was pressure forcing the coolant out. The temps of the coolant never reached 200*. The hottest temp on the motor read 240* and that was the exhaust port on the head. The bubbles were very tiny at start up and turned into what appeared to be a hard boil once I was able to see flow in the radiators.

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I also suggest you check your head for warpage, but not with a straight edge....the low spots can be almost undetectable to the untrained eye.  Get some 120 grit or fine sandpaper and put it on a machined flat suface like corian or plastic laminate countertop that is nice and flat and rub your head on it , not back and forth , but in all directions changing directioins all the time.  Your will see just how uneven your head is.  Then buy a quality head gasket and put it back together and see what happens.  Prolly be fine, but as a warning if your engine is running rich or lean it can heat up real quick, might have just been that, but at least you will know for future.  dowel pins or alignment pins will pull out with pliers.

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I'm unsure if my engine was running rich or lean. It has the stock carb and the yosh rs4 dual exhaust. I imagine this is running a bit lean from the new exhaust and no carb work but I cannot tell. The plug is still on the fuel screw on the stock carb and I am at sea level. Perhaps I have a carb that needs tuning and is causing unnecessary heat build up. I have not don't the 3x3 mod. Just stock carb with exhaust from previous owner. It sounds good and pulls hard. No flat spots or smoke.

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Shanecarrs suggestion is how to check for low spots. As you sand the head surface and the barrel if need be .Do it  and look for areas that are still dark. That will be the low spot. More likely than not it will be just above the exhaust port.

 

good luck

 

Tony

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I will take some fine grit sandpaper and find out where the high spots are on the head. Would 120 or 180 work for this? I think 80 would gouge the aluminum and cause more problems. It appears to be straight and level but that may not be the case.

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