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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 8499
Experience:  23 Years Caterpillar Engine experience.
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hi i have cat engine 3406E , i had a problem is water in the

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hi i have cat engine 3406E , i had a problem is water in the coolant system, what should i do now? please help.
Hi. Thanks for using JA! I will try and help you out.

I would drain the oil and pressuroize 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 5 years ago.
no i am wrong not water in coolant, i had 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 5 years ago.
and could you let me why it cause the injector cup o rings fail, just because of it too old or coolant need to replace regularly ,or all the injector not working propperly 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 # XXXXX please. that all i need. 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 too fail.

I can get you the part numbers you need, it will take me a little while but I will back soon.
Customer: replied 5 years ago.

yes sir, iam waitng 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 number are:





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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