Prestone Coolant Flush Kit Okay?
 

The vehicle is a 1990 420SEL with just over 170K miles. I want to flush the coolant, but do not want to take a chance on screwing up with the citric cleaner. Is the Prestone backflush kit okay to use on these cars? Would the typical splicing into the heater hose be the prescribed method? Any help or advice would be appreciated. Would especially like to hear from owners who have had success with the Prestone or other backflush kit. Thanks in advance.

This is what I used, I guess it worked, I can't see through the motor.

http://www.valvoline.com/pages/products/product_detail.asp?product=15

I installed Prestone backflush kits to several Honda's and a Lexus heater hoses without any problem. Flushing radiator coolant with this kit is very easy and fast too. I never had any leak around the T.

I did not try it on my 00 E430 so that I am not so sure if it'll work on it.

My friend had one of those T's on her car and after a couple of years it cracked and leaked. You could probebly do as good a job by just opening the 2 drains and taking off the thermostat. I don't know how easy that is in your car. Mine was pretty easy. I wouldn't want that Prestone thing on my car. A radiator guy told me not to use those cleaners also.

German Engineers
 

'Know the most efficient and safest flush method.
They provide it in the FSM.

I would be very wary of "Flushing" with anything like the Valvoline product...
TOO much chance of "Breaking Loose" something that will get lodged in one of
the internal cooling passages of the engine,heater core or radiator.

If you've always used either MB coolant or the Zerex G05 AND have De-oiled
and Citric Acid Flushed as per factory schedules;Then a timely Citric Acid Flush
(With De-Oiling prior) would be in order.

If you have no idea what service routine has been carried out in the past
It's a Crapshoot!

The Factory procedure is time consuming...3-4 fresh water flushes (at eng. OP temp)...
then De-oil...Flush(s)...Citric Acid flush...Flush(s)...then refill with
DISTILLED water and coolant.

Personally, I would rewrite the specifications to de-oil AFTER citric acid flush. This is because de-oiling would neutralize the residue after the citric acid treatment. I see no benefit to doing the de-oiling treatment first.

I suspect that the reason for the de-oiling is to reduce the amount that the acid is neutralized by the residual coolant in the system.

That being said, I can't see how a soap (de-oiling agent) would do that much to neutralize the acid. Better to wash through a mild solution of baking soda during one of the first rinses, if you're truly worried about it.

Deoiling would leave even a higher pH than the coolant, and make it tougher for the acid to be efficacious. So the prescribed coolant treatment sequence can't be for that reason.

I often acid-treat metals in the lab. This is followed by a neutralizing treatment, accomplished with dilute ammonium hydroxide. When I run out of ammonium hydroxide, I use simple soap. If I do nothing, the metals continues to rust, no matter how many times I've rinsed the part with water.

If you want, you can use an extra piece of the same size hose, and install the T without cutting the original hoses, just disconnect the original hose where convenient, connect that end to the T, and connect the other end of the Tee with the extra piece of hose. Then when done, the T can be removed and the original hose reinstalled without the worry of leaving the T there. I tried leaving the T installed once, and it leaked because it got crushed and deformed by me overtightening the clamps.