Hello Everyone
I am new to the forum. I just purchased a 1993 Sedan Deville with the 4.9 PFI motor. My car has just 64K miles ( I verified that several ways) and I have had it for about a month and so far very happy with it.

I am hoping I can ask for some advice and in return in the future , I can reciprocate as I gain more experience.

Immediately when I brought the car home I changed the oil and reset my Oil life indicator. Knowing that my cooling system needs to be maintained top notch being as I have the aluminum block motor and I got the car with no service records, I think I should immediately flush and refill the cooling system. Upon initial inspection, The antifreeze mix in the radiator now is a very healthy looking green and topped right up to the cap ,but as mentioned, With no service records, I cant be sure the mix includes the GM cooling supplement tablets or Bars leak gold which appears to be crucial seeing as how its mentioned constantly when discussing the cooling system on these cars and I also have a decal on the radiator warning that it needs to be part of the cooling system upkeep.

My question is, Would draining the radiator be enough or do I need to completely reverse flush the system removing coolant from the block and heater core and all hoses as well?

Whether I simply just empty and refill the radiator or do a complete reverse flush, Should I use distilled water as part of the new mix? I will most certainly add the GM or Bars leak gold supplement. At what time during the refill should I add either of these supplements?

I think I read that simply refilling the radiator and being certain the coolant supplement is in is the most important but if an entire flush must be done im not opposed to doing so. If a complete flush must be done it might be something a mechanic must do, A simple drain and refill of the radiator I can do. Last time I did a complete flush and refill was in 1988 on a 1984 Camaro Z-28 I owned, MUCH different and not as crucial to be done in detail as this car with the aluminum block must be.

Doing a simple drain and refill of the radiator means I know that distilled water will be used and im guaranteed knowing that the cooling supplement is in fact added. No offense to any mechanics here on the board but I don’t trust of a lot of them around my area.

Also after looking closer after I bought the car, I noticed a sticker on the transaxle that read “GM Service Replacement Transmission” Is it possible my transmission was replaced at one time? If so is there anything about the transmission in these cars I need to know as far as upkeep that is particular just like the cooling system on the engine? I don’t beat on this car, I never will, I don’t have a lead foot or plan to drag race it, It appears this car was never pushed hard before I owned it as well. The trans fluid now is really bright red and no burning smell and shifts excellent right now. I would like to keep it that way.!

Thanks for the help, I look forward to any reply!

Going by your description, I would say a drain and refill would be sufficient. Distilled water is always a good idea, prevents scale buildup and other nasty junk.

As far as the transmission, It may have been replaced early in its life for some warranty reason. There's no real major issue with the transaxles in these cars other than there slightly undersized for the application in my opinion. (they were usually stuck behind V6s) That's not to say theres any longevity issues, many people report an average lifespan of 130k before any issues. The issues are usually a "Service Engine Soon" light appearing during highway driving with a code E39. Some people ignore it and go another 130K, some people end up having more problems shortly after. That pretty much puts it on par with most cars. That engine though is one of the best of the bunch, very reliable albiet with a quirk or two. (like needing the tabs)

Congratulations on your car, sounds like a real beaut. When you get a chance, post a picture or two.

Thanks for the advice! Much appreciated. I am posting a photo of my 93 Deville. hope i did it right!

If the coolant contained GM supplement it would look dirty and rusty. Most likely it does not contain that. Do you have enough heat? If so, just drain and refill with green 50/50 mix. You can add supplements into the radiator neck at any time. It's easier to add the supplemet before you top the radiator up. Nice Deville, BTW> take good care of it! :)

Ok thanks! I likely have no supplement in there so im not going to delay any further on changing and adding. Here is another pic.

Sharp! Good luck with her!

Thanks! I hope you didnt mean good luck like im going to need it! :)
Another question i hope you (or anyone) wouldnt mind helping with.

Is there such a thing as adding too much of the coolant supplement tablets? I ask because im considering just adding the tablets (just picked some up at Cadillac Dealer) to the current mix without draining as im not sure if any were put in by previous owner but the mix looks very strong....reason i suggest this is i hurt my back just recently and getting underneath the car right now is a problem. So if the current mix in there has them,is more worse or should draining just be an absolute that should not be avoided?

Thanks!

Pick up a Prestone Anti-freeze tester at Auto Zone - about 6 bucks (looks like a small turkey baster), draw some coolant from the top of the rad, and check the color. If it's pure green or orange, there is no coolant supplement. If it looks like really dirty dishwater, then the supplement has been added.

Yes, you can put in too much, and that can clog the heater core. etc. Use no more than the four or six tabs that come in the GM blister pack.

Thanks! good idea since doing it that way ,One can see the collant further in. Actually she is going in today to get flushed and refilled. Found someone who i can trust around here and knows these cars good. Interestingly enough i opened cap yesterday and just checking things again and noticed some "goopy" like accumulation under the cap...Also noticed that in my overflow reservoir there is some accumulation of light brown goop similar to what was under the cap which looks very much like the GM cooling tablets i have. The brown stuff was above the fill line in the reservoir. Got another pic....The long vertical tailights that goes back to the classic Cadillacs is one of many things i like about this car.

Thanks! good idea since doing it that way ,One can see the collant further in. Actually she is going in today to get flushed and refilled. Found someone who i can trust around here and knows these cars good. Interestingly enough i opened cap yesterday and just checking things again and noticed some "goopy" like accumulation under the cap...Also noticed that in my overflow reservoir there is some accumulation of light brown goop similar to what was under the cap which looks very much like the GM cooling tablets i have. The brown stuff was above the fill line in the reservoir. Got another pic....The long vertical tailights that goes back to the classic Cadillacs is one of many things i like about this car.
Looks like you have supplement installed.

Yes the more i looked at it despite the coolant appearing green, It did in fact have the supplement...But i had it flushed and filled anyway so i know when the coolant was in fact changed and supplement added because i had no service records from this car,And even though it most certainly appears to have been very well maintained when i looked at it to buy,I did not know how long it was in there...Now i know....Good until next year at least.

Odd thing, Today i brought it for state inspection. On the drive over the anti lock dash light when on as i hard braked behind someone who jammed on their brakes. Also felt a very prounounced stutter as i did it from the brake pedal.

Made it ok to garage and light went out before i arrived.Nonetheless while car was on the lift at the garage, Inspector had a problem getting rear drum off the right side. He finally got it off, Brake pads ok and car passed. I noted when i got back on the road, pedal a tad bit softer yet more responsive. Wondering if the stuck drum might have triggered the Anti lock alert ?

Hey beautiful Cadillac there. You bought it from me. If you did the radiator flush I hope you put the coolant supplement back in. Im glad the car is working out well for you

Hi George
Small world! .. I been doing more driving of the car than my Mom has ..who i bought it for !..and so far so good.

I think the only thing i need to do right now is fix a rich fuel mix and i think the throttle body has some carbon build up. The gas mileage has been pretty poor as a result but other than that car is ok.

very nice car with great miles. Congrats!

Thanks!

As far as the sticker about your trans, we have had 6 4.9 cars in the family, 4 of them purchased w/less then 10k miles.
2 of the low milage cars had an issue with the way the tranmission fluid line was crimped, which caused the lie to come loose, the both times was getting the tranny replace both times under warranty, and they have the sticker. This made us decide to have all of the cars inspected just to be safe; what we were told was that although it was not really comon, there were cars that had defective lines (and when the line blows, you dont go).
As a side not, like one of the other posts said, the trans is the weakest link in the driveline, as it is a little small for the application. We typically change the fluid and filter every 50K; but whatever you do DONT let anyone FLUSH the system....in my short lifetime, I have had to replace 2 transmissions due to this.
And for what its worth,
93 seville 4.9, burgandy w/145k trans replaced at ~40k
92 deville 4.9, white w/165k, original trans
92 deville 4.9, burgandy w/247k trans replaced at ~22k (i think it can drive itself from San Fran to Maryland)

Interesting to know! Thanks for your input on the transmission. Yes i am in full agreement with you on the transmission flush. Its unneccessary for as it is just a service to add money to garage`s pocket as its easier money for them to do needless flushes on a few cars than a repair that might have a slimmer margin.....and i have heard from others that its cost them a transmission!