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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 26515
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a 23HP liquid cooled Kawasaki engine on a Scag commercial

Customer Question

I have a 23HP liquid cooled Kawasaki engine on a Scag commercial mower
Last time I used it, it was hard to start. Usually starts right off. After mowing for about 30 minutes, I lost some power. Dropped a cylinder.
I shut it down right away and noticed the antifreeze over flow tank had turned black.I took in to the dealer and he said I blew a head gasket.He replaced it, it started right up. He let it run awhile till it got up to temp. and it blew another head gasket. He replaced it twice more with the same results. Now he wants to replace the engine. Do you think I could have a plugged journal and the head overheated and warped? I constantly watch the temp Gage and has never overheated.
Submitted: 6 years ago.
Category: Small Engine
Expert:  Curtis B. replied 6 years ago.

curtis b :

You don't mention if the thermostat was changed and whether the water pump has been checked. These liquid cooled engines are not tolerant to overheat and anytime you have a head gasket blown, the thermostat should be changed and the water pump checked. Also when filling the system, all he air has to be bled out or the cylinder heads will overheat and blow the gaskets. I think you have a coolant circulation problem. Replacing the engine is a cop-out to me. There has to be an explanation for the problem.

Customer :

Hi Curtis

curtis b :

I am here.

Customer :

After taking with the dealer today, i gave you some false information. When he told me the he had the same results after changing the head gasket I took that it blew the new head gasket. It did not,when I brought it in to him the head gasket was bad and the antifreeze overflow was black in color. What it is doing when it warms up, is blowing exhaust or combustion gases back into the antifreeze overflow and it looses compression in on cylinder (The same cylinder each time. It does not blow the head gasket. My guess would be a bad head. Cracked valve seat maybe. I still don't know why he is pushing a new engine. He replaced the thermostat and water pump. Thanks Don

curtis b :

Compression in the coolant is almost always a head gasket. With no history of overheat I wouldn't expect head to be cracked.

Customer :

would it be smart to have the head magnaflexed

curtis b :

I assume the head was checked for warpage and the block surface. I don't thing magnafluxing will show anything. Usually only used on large cast iron heads.

Customer :

He told me he checked the head and was not warped. What ever is going on is failing when the engines warms up then is ok after it cools down and does the same thing over again when it warms up. I running out of things to have him check.

curtis b :

For the unit to loose compression and not blow head gasket doesn't sound plausible. If the head was the problem, why does it work until unit reaches full temperature? How do you feel about the dealer? Do you think they know what they are doing, or they just trying to sell a new motor? The Kawaski is great engine and is used in most of the Deere equipment. I can't see why this should be such a problem. ??

curtis b :

If it were mine, I would pull both heads and check and replace gaskets and then when putting it together, I would swap the heads. This would let me know if the head was the problem, if he problem changed cylinders.

Customer :

He has been around a long time, after talking to him he may not have alot of faith in his mechanics. He told me he was going to lot at it himself. That's a good idea. swap heads I will suggest that to him and let you know the results Thanks Don

curtis b :

ok, with this having been done three times, it sounds like the old insanity. doing the same thing, expecting different results. Let me know. Thank you.