4.9L and coolant seal tabs

[Daniel]

I just bought a 1992 Sedan Deville (4.9L), my first Cadillac, and am doing some maintenance including changing the coolant (never done as near as I can tell).  I plan to flush the system, add new antifreeze, etc. but am totally confused about how many of the coolant seal tabs to use.  The dealer has 10g and 4g tabs, but doesn't know how many I'm supposed to add.  Some internet searching has left me totally confused.  Help.

[Dave Shepherd]

On that engine I would use 4 large tabs, grind them up and put them in about 1/2 thru the refill.

[CEC #20099]

CEC # 20099
I have a 90 4.5 & always use 1 large bottle of BAR`S LEAK, with a 50/50 fill of Prestone. I do this every 2 yrs, & my cooling system is spotless. DO NOT use Dexcool antifreeze. The Bars`s leak dissolves quickly, unlike the tablets.
This is all because of Cadillac`s sorry engineering. It is a band aid to stop the internal leakage.

[TJ Hopland]

My memory is not what it used to be but I thought that you were supposed insert them in one piece (if they would fit) and it was supposed to be a sort of time release thing?    I checked the pack I have in the garage and it just says crush if needed.  Seems like the older packs had more detailed instructions.  My pack has 6 in it and says use 'entire contents'.  As long as you are getting a complete flush I dont think a full pack will be too much.

[76eldo]

First, never powerflush or reverse flush any of these engines.  Open the radiator drain and let the coolant drain out.  Close it up, and fill with water, and start the car with the heater on hi temp and hi fan.  Drain it again. You may have to repeat this several times, or just let the car run with gentle garden hose pressure flowing into the filler, and let the car run with the radiator drain opened up.  Yeah, I know it's not "green" to do it like this, but it's one way to do it.

Too much pressure could cause a problem with a headgasket that is holding, but could be weak.  I have had good and bad HT4100's, and these procedures all stem from that motor's problems.

I always ground up all 6 and added it to about a quart of antifreeze.  I pour about half of it in, followed by a gallon of antifreeze (straight).  Then I start the car, and add water until it is fairly full.  Keep running the car until the thermostat opens up, and keep track of the ratio of antifreeze to water, and keep it to as close to 50/50 as possible.

Turn on the heat, and drive the car for at least 15 minutes to circulate the coolant completely.

Good Luck,

Brian

[TJ Hopland]

When I have had a flush done it looked to me like it was like the garden hose method except it drains into some sort machine /tank.  I thought the 'power' part was just the chemical part?  I let em use it on stuff I have owned since new but have them skip that part on engines I dont know the history on unless I have a rebuild in the budget.

My point about the flush is that you are getting most of the last batch of stop leak out rather than just adding more and more and more.

[Guidematic]

 The actual GM recommendation is to add 2 of the tablets. Too many can plug the heater core.

The preferred method is to add them when the engine is hot and the coolant is circulating. You can add them whole or crushed however you prefer.

Mike

[Daniel]

Thanks for the responses.  I've got recommendations from 2 to 6 tablets--I guess I'll split the difference?  It's strange there isn't an absolute number out there; maybe it's not all that critical.  I assume you are all talking about the large (10g) tablets?

[Guidematic]

 It was 2 of the large tablets that were to be added. They supplied a package of 6. If you have the large ones, don't add all 6.

Mike

[Ohio57-62Sedan]

The magic number is two.... and I only use the GM pellets ..  bars leak and others will clog the heater core. you can use iron tite ceramic its the same compound as the pills.
and if power flushing causes you grief the tabs are not goanna fix it anyway.. I do like to flush out a dirty cooling system if you break something in the process.. it was bad from the start..
remember there is no such thing as a mechanic in a bottle and I don't care what anyone tell's you..

the absolute number is two...