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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 8951
Experience:  23 Years Caterpillar Engine experience.
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3406e Cat engine problems. I have water in the coolant system

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I have a Cat engine 3406E. I had a problem - there is water in the coolant system. What should I do now? Please help.

Hi. Thanks for using JA!

I would drain the oil and pressurize the cooling system so you can see where the coolant is coming from. It could be a liner or a head gasket or possibly a water pump. Let me know if you need more help.

Customer: replied 6 years ago.

I am wrong, not water in the coolant system; but diesel in my coolant system.

Oh I see. If you have diesel fuel in your cooling system, your engine has had an injector cup O ring failure. This problem is not hard at all to get fixed. The injectors will need to be removed and the cooling system drained. There is a special Cat tool needed to remove and install the cups. You most likely only have 1 or 2 cups leaking but I would recommend replacing all of the injector cup O rings. If you don't, another O ring may fail soon after and you'll have to do this again.

Please let me know if you need more help.

Customer: replied 6 years ago.

Could you let me know why it caused the injector cup o rings to fail? Just because of it was too old or the coolant needed to be replaced regularly or all the injectors were not working properly in other? And do I have to change all the injector o rings? If I do what should I buy - the right things and please give the parts # too please.

Thank you

The O rings will fail when the engine gets a lot of miles on it. It is also possible that if the coolant conditioner in the antifreeze is too high, it can cause the O rings to fail. I can get you the part numbers you need, it will take me a little while but I will be back soon.

Customer: replied 6 years ago.

Yes sir, I am waiting for your parts number that I need to solve my problems.

Thank you

Thanks for the information.

The tool that you need to remove and install the injector cups is 9U-6891.

Each cup has 3 different O rings. The part numbers are:

9 X-7 4 3 0

1 6 6-2 9 0 3

1 6 6-2 9 0 4

If you plan on doing them all, you will need 6 of each.

Please let me know if you need more help.

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