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Small Engines (Lawn Mowers, etc.)/FD620D AS17 KAw engine trouble


QUESTION: replaced head gaskets, repaired head and block surface, thermo side cylinder, due to corrosion.  back together, coolant leaky from head, does not appear to be going inside cylinder, dry,   breather tube inside airfilter is blowing water/ white film. Is that possible?

ANSWER: How did you repair the head and block?  Have you performed a compression leakdown test to see if the head is leaking?  Do you have a vaccum gauge to see if the engine is maintaining a little negative pressure (vaccum)?

Did you download the service manual?

Have you performed a cooling system pressure test?

Let me know.

---------- FOLLOW-UP ----------

QUESTION: I had the corroded areas, repaired by a aluminum welds and milled to even the surface on the head. The other smaller corroded areas on the block I used the steel weld epoxy to replace the gaps.  Smooth it with emory paper.

I dont know what a comp leak down test is but I did put a compression gauge in place on each cylinder, did not reach 170psi, advanced the engine by rotating the fan.

I was following the service manual, throughout the process.  The coolant is leaking from the outside surface between the head and the block, just next to the exhaust manifold.

I did not try a cooling system pressure test.

After I rebuilt the engine, re-filled the oil and coolant, I started the engine without issue, it took a 1-2 minutes before the coolant started leaking out.  After a few minutes the temp light went on, that when I turned it off.


With all that work being done you really need to do a cylinder leakdown test and a cooling system pressure test to determine where the leak is coming from.  I've had similar issues with larger water cooled engines in the past and it required the special tools to perform the pressure tests.  FYSA, I've seen machine shops miss cracks in cylinder heads.

The URL below is a decent article on cylinder leakdown testing.


Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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