G5200 clogged block?

[TexanNB]

Hi Everyone,

Largely thanks to this forum I bought an early 90s G5200 that was supposedly restored. Unfortunately she overheats and as I started digging into the laundry list of potential causes, I've found that the coolant stop cock on the block is completely clogged with scale/gunk (I know because I tried to remove the 'bolt' and it immediately broke off). Tried slowly drilling out the hole with a small drillbit but didn't want to go too deep in fear of drilling into something I shouldn't be. No coolant came out.

So my question is, how can I clear out the flow channels (if that's what they're called) to at least flush the block? I am pretty sure the water pump is leaking so I was going to remove that next but I don't know what the coolant channels look like inside the block and whether I'll have any hope of unclogging them?

Thanks for any advice/help y'all can provide.

-Derek

 

[North Idaho Wolfman]

Very unlikely that the block is clogged up, it very likely that the drain valve was clogged.
you going to have to get the broken valve out of the block, and replace it
Do not drill it it's hollow and it's just sediment, if you drill into the cylinder wall behind it the motor will be junk.

 

[TexanNB]

Very unlikely that the block is clogged up, it very likely that the drain valve was clogged.
you going to have to get the broken valve out of the block, and replace it
Do not drill it it's hollow and it's just sediment, if you drill into the cylinder wall behind it the motor will be junk.

Thanks for responding. Any tips on getting the valve out of the block? I'll get a photo in the morning if that helps.

 

[BruceP]

Too bad you did not ask BEFORE breaking it off....we could have talked you through the procedure.
We also could have told you that those machines (G series) tend to run hot. The AIRFLOW THROUGH THE RADIATOR is very important.

• Clean the radiator dust-screen EVERY COUPLE HOURS of run-time.
• Make CERTAIN the battery is not blocking the air into the radiator.
  • mount battery as far from radiator as possible
  • DO NOT install larger battery..... engine will overheat.
• Keep the air intake vents clean (on both sides of machine)
• Use garden-hose to clean outside of the radiator THOROUGHLY.
  • DO NOT use high-pressure water... it will bend the radiator fins.
  • make sure water passes thru radiator-fins from both sides.
    

====================
It is VERY common for the block-drain to be clogged like that.

1. Use small drill-bit BETWEEN YOUR FINGERS to gently ream out the drain.
2. Then, move to larger drill-bit BETWEEN YOUR FINGERS to gently ream out the drain.
3. If, at any point anything comes out besides crud. (like metal shavings) STOP

At some point, the coolant in the block will drain out.
...now you have the problem of plugging the hole now.

================
ALTERNATIVE
Leave the block-drain plugged up
Instead, drain the block by pulling bottom radiator-hose from radiator. (this also drains radiator)
Use leaf-blower to blow air where the radiator-cap goes.... this will drain any residual coolant.

==============
To get to your REAL problem (overheating)
Fill engine with DISTILLED WATER... run for 10 minutes....drain
REPEAT the above until it drains clear. (may take 3-5 times)

Each time engine is running, use point-n-shoot thermometer to check the temperature of UPPER hose and LOWER hose. WRITE DOWN THESE MEASUREMENTS. This will guide you to why your engine is overheating.
You need to determine if the coolant is flowing, is the radiator removing heat....etc

 

[Torinodan]

Broke mine as well. The drain is made if really soft metal that eventually seems to rot away from the inside out. Small drill bits twisting by hand to clean or a small bore brush in a drill. Take it easy. There was enough material left from the old drain to tap some threads in it and install a bolt to plug the hole.

 

[woodman55]

Has any one tried CLR ? I would think it would help a lot. Then do the normal flush.

 

[Torinodan]

I flushed first to remove loose sediment then some CLR. Have to get the loose stuff out first, check your temps, then move to chemicals if needed. Flush the radiator as well.
BTW, CLR can help you find small leaks you didn't know about.

 

[BruceP]

Has any one tried CLR ? I would think it would help a lot. Then do the normal flush.

I flushed first to remove loose sediment then some CLR. Have to get the loose stuff out first, check your temps, then move to chemicals if needed. Flush the radiator as well.
BTW, CLR can help you find small leaks you didn't know about.

WARNING: I actually used a commercially available cooing-system cleaner. (mildly acidic)
Followed the instructions to the letter and a LOT of rust-colored crud came out of the cooling-system.

https://images.thdstatic.com/catalog/productImages/1000/80/80537421-1b50-42a9-b391-f6d100e09918_1000.jpg

HOWEVER: My waterpump-seal (around the shaft) began leaking about a year later. i suspect, the acid-wash damaged it.

HENCE: I replaced waterpump using NON Kubota part. THIS WAS A MISTAKE!!!!
After initial bolt-up of new pump, IT WOULD NOT SPIN BY HAND because the impeller was rubbinbg on the inside of the engine.
Ended up using dremel-tool to grind the impeller to increase clearance inside the engine.

THUS: I strongly recommend everyone who uses "CLR" or any other means to clean cooling-system to expect waterpump to start leaking.... and only use OEM Kubota spare parts.

 

[Torinodan]

THUS: I strongly recommend everyone who uses "CLR" or any other means to clean cooling-system to expect waterpump to start leaking.... and only use OEM Kubota spare parts.

Easiest way to find any point of failure on an old G series mower with poor cooling. I agree and water hose followed with distilled water flush. Mine was heavily rusted and a failure was going to happen anyway so I went the fastest way to find them.

 

[TexanNB]

Thanks y'all.

Ran at low rpm for 10 min. w/distilled water. Upper radiator hose 140F, lower hose 118F.

My radiator cap says 7psi. Is that correct?

Attaching some photos. PO put what appears to be a non-oem thermostat housing on there.

All screens are clean and airflow coming into the "air box" near battery is 100F (hot day in Texas). Is the battery too big/too close to the radiator? It's probably at least 1-2" away.

When it cools down enough I'll drain the distilled water and maybe flush radiator with the hose, then do some more distilled water flushes.

Drain on block still clogged. I'd really like to flush out the block if I can.

 

[Torinodan]

Battery is way to close. Tie that thing back centered to the steering column. Overheat central right there!
Fix that drain before it magically opens itself up. Hey, things happen!

 

[DustyRusty]

I would use a commercial block cleaner and then rinse and neutralize with a box of baking soda. You will be surprised how much rust is still located inside the block. I use Arm & Hammer washing soda in place of a commercial cleaner and pull the lower hose to drain the block. Then I start over again when the block is cold, fill it with clear water, and add a cup of washing soda. Run till it is hot, and drain. I do it until the white liquid going in is the same coming out. No thermostat in the system for cleaning. I have done this many times and have never damaged a water pump, but I have found an occasional leaking freeze plug when all the rust is gone from it.

 

[BruceP]

Ran at low rpm for 10 min. w/distilled water. Upper radiator hose 140F, lower hose 118F.

Those temp. readings suggest the radiator is dumping some heat into the air.

My radiator cap says 7psi. Is that correct?

The ENTIRE machine is metric.... I would not expect PSI to be on the factory cap.
Factory cap says 0.9 Bar on it which converts to 13.0534 PSI
Kubota P/N for radiator cap = 15272-72020

Part Details | Coleman Equipment

All screens are clean and airflow coming into the "air box" near battery is 100F (hot day in Texas). Is the battery too big/too close to the radiator? It's probably at least 1-2" away.

That battery is WAYYY larger than mine.... and blocking a large portion of the radiator-intake

Drain on block still clogged. I'd really like to flush out the block if I can.

I would not mess with it.... popping the lower hose does the same thing.
Think it through....

• IF you can successfully drill the crud out so it drains
• IF you can get the remnants of the broken piece out without damaging threads
• IF you can get ahold of a replacement drain (remember it is METRIC)
  • Kubota P/N for drain-valve = 15841-73020

  • Kubota #15841-73020 COCK, ASSY DRAIN

    COCK, ASSY DRAIN

    www.messicks.com

You can lookup Kubota parts for yourself here:

Kubota Tractor Corporation - Illustrated Parts List

- K-PAD - Parts Lists - Illustrated Parts Lists - diagrams

apps.kubotausa.com

 

[TexanNB]

Thanks everyone for the feedback. I ordered the correct radiator cap and plan to do some flushing of the radiator and block tonight.

Re: the Battery. What smaller battery do y'all use? The one in there seems to fit the bottom bracket and I have read about folks re-locating the battery to the front or back of the tractor.

 

[TexanNB]

UPDATE: to see if the water pump had failed, I temporarily replaced the upper radiator hose with a clear one and removed the thermostat. The coolant was NOT flowing. Does this mean the water pump is bad OR will coolant not flow right away after start up? I left it idling a minute or two and NO flow...

 

[North Idaho Wolfman]

UPDATE: to see if the water pump had failed, I temporarily replaced the upper radiator hose with a clear one and removed the thermostat. The coolant was NOT flowing. Does this mean the water pump is bad OR will coolant not flow right away after start up? I left it idling a minute or two and NO flow...

Dead water pump!

 

[GeoHorn]

I’ll add Two items which I’ve experienced over 7 decades:

1- Cooling system “cleaners” will ruin your water pump.

2- Water pumps can fail in other ways than leaking….. I’ve had TWO pumps fail to rotate their impellers despite the pulley operating just fine and No Leaking. In this type failure, NO WATER MOVEMENT is possible. In one instance the impeller was eroded so badly the ”flutes’ would not pump water. In the second instance the pump pulley and shaft rotated fine…but the impeller was loose on the shaft and did not spin with the shaft…..and could not impart any movement to the water.

 

[TexanNB]

I’ll add Two items which I’ve experienced over 7 decades:

1- Cooling system “cleaners” will ruin your water pump.

2- Water pumps can fail in other ways than leaking….. I’ve had TWO pumps fail to rotate their impellers despite the pulley operating just fine and No Leaking. In this type failure, NO WATER MOVEMENT is possible. In one instance the impeller was eroded so badly the ”flutes’ would not pump water. In the second instance the pump pulley and shaft rotated fine…but the impeller was loose on the shaft and did not spin with the shaft…..and could not impart any movement to the water.

Gentlemen, Thank you for confirming. Guess I'll have to order one. I've learned from those on here to go OEM due to impeller clearance issues but dang, $200+

 

[GeoHorn]

Gentlemen, Thank you for confirming. Guess I'll have to order one. I've learned from those on here to go OEM due to impeller clearance issues but dang, $200+

Another reason to go “OEM”….. Seals on OEM are Top Quality…while some/many aftermarket products are “price-valued” and use substandard bearings and seals. OEM has the longest service lives.

 

[DustyRusty]

My formula for washing soda cleaners will not hurt your new water pump. It cleans the block gently loosening up the rust and keeping it in suspension till you pull the lower radiator hose. I can't impress you enough that you must wait for the block to be cold between treatments so the cold water doesn't crack the hot engine. It is time-consuming to wait to do each treatment, but the results will be worth the time spent.