Adding extender to antifreeze

[RLS]

I posted this on the Cat forum and got no response, so I thought I would try it here.
I have a rear radiator Freightliner coach with a 3126E. I had the cooling system flushed and changed to Cat ELC a while back. It is now time to add the extender. My question is can I just add it to the over flow tank or do I need to open the radiator and pour it in direct?

[Gary RVRoamer]

Already? Typically the extended for ELC is added at 300,000 miles?

But I don't know the answer to your question. If the tank is an active part of the system it is fine to add it there, If it's just an overflow, the contents may not get mixed in very soon. Or at all. MAybe a call to Freightliner? They installed the radiator system.

[RLS]

Thank you for the reply. I was hoping someone on one of the forums had added extender to their coach. I was told by Cat that 300,000 miles or 3 years which ever comes first. I guess a call to Freightliner is in order.

[DonavonP]

If your manual tells you to check the level of coolant in the overflow tank and it has a hot and cold level indicators, it's probably part of the system. You can verify this by marking the level when it's cold and then when it's hot. Should be several inches difference.

Also, if I remember correctly, the test strips available for checking the PH balance have instructions to use the overflow tank fluid for testing. Been too many years since my diesel pusher.

[sknight]

Yes you can add it to the surge tank, it'll take a few drive cycles to balance out.

[MrTransistor]

What sknight said, but it should only take a few minutes to mix. The two small hoses connected to the surge tank return coolant from the high points in the engine then it flows back down the large hose to the water pump to combine with the normal intake of the water pump. That is why there is a baffle in the surge tank, to divert that stream of coolant instead of it squirting straight at the large cap at the other end. Poor design because it’s so hard to get the small cap with the diverter to seal but it gets the job done for a year or two until it has to be replaced. We are on our fourth tank! Thinking about having one made by a radiator shop out of heavy gauge brass with a sight gauge.