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Cadillac 1993 Deville 4.9, 1991 Eldorado Touring Coupe
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Discussion Starter #1
I bought my 93 Deville (4.9) in December 2006 and although the coolant looked perfect, I flushed out the system and added the GM pellets (6) Just so i would know when it was done since i didnt have any service records from purchase.

I read all the time from most posters on this subject that the coolant and supplement should be changed annually. I dont really question this but just wondering why it is absolutely necessary.

Would every 2 years or up to 5 years be ok? Anyone with any experience extending the annual interval idea?

How about the use of Anti Corrosion supplements? Anyone with any experience here? The use of it helping anti corrosion and its ability to mix ok with the pellets?

To me the idea of changing coolant is avoid coolant breakdown which also promotes corrosion, So if using an anti corrosion, can you extend intervals?.

Or is the idea of the annual coolant change a requirement due to the use of the anti leak supplement and its needing to be replaced very frequently?... or the fact that the 4.9 is an Aluminum block requiring coolant changes more frequently. If so, I dont have a problem changing the coolant frequently for any of those reasons.

But most cars i have owned have been a 3 to 5 year interval changing coolant only due to its breakdown.
 

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1995 FWB 128,*** miles
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2,255 Posts
Silicated (green) antifreeze is good for two years. Nevertheless, I replace it partially every year and add a tube of Bars Leaks powder (same stuff GM pellets are made from). Because I siphon coolant through the radiator neck it is not messy and takes some 15-20 minutes. You can get about 1.5 gal of old coolant.
 

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Cadillac 1993 Deville 4.9, 1991 Eldorado Touring Coupe
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370 Posts
Discussion Starter #3
Thanks for reply HUF. How do you siphon? Do you have some kind of pump for that?
 

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1995 FWB 128,*** miles
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2,255 Posts
Thanks for reply HUF. How do you siphon? Do you have some kind of pump for that?
Just get some 5-6' of PVC 1/4" OD ( or a little bit more) tube from a hardware store, fill it with water and squeeze it into the radiator neck between the side tank's wall and the internal oil cooler so that it would reach the bottom. Block the other end with your finger while you do that. Lower the free end to the pan on the ground and open it up. The old coolant will slowly siphoned. No pump is needed. You will not get all the coolant , but I think partial ANNUAL replacement is enough, and it is fast, easy and not messy at all.
 

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2006 CTS
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258 Posts
zentrade,

I have just about the same question as you as far as changing intervals. I just changed mine yesterday for the first time (Just bought my '93 Deville last month). I did an extra special job, flushing the radiator, engine and expansion tank. I even took the expansion tank out to do a better job of cleaning it. I poured in new anti-freeze and used distilled water to boot, along with 6 new GM tabs. And it sure seems like it will be too soon to do it all over again in 12 months from now.

I'm sure the answer that we will be getting is mainly because of the aluminum engine and the head problems these cars sometimes can have.

You mentioned that some of the cars you have owned were changed at 3 to 5 years. Up till last month, my newest car ever was a '72 (Chevy Impala). I've been owning old Chevys now for about 35 years and never once changed the coolant because of maintenance. Just when I was changing a water pump, radiator, etc and would think that the coolant looked a little old.

But I did learn in general and on here as well that these cars need different maintenance on them.

HUF,

I read where you partially change your coolant and if I'm correct, you are leaving about 2 1/2 quarts in there, but adding 6 new tabs everytime. I'm just wondering if thru the years, you would have a much higher sealant ratio than called for and wondering if that would be OK?
 

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1995 FWB 128,*** miles
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2,255 Posts
zentrade,

I have just about the same question as you as far as changing intervals. I just changed mine yesterday for the first time (Just bought my '93 Deville last month). I did an extra special job, flushing the radiator, engine and expansion tank. I even took the expansion tank out to do a better job of cleaning it. I poured in new anti-freeze and used distilled water to boot, along with 6 new GM tabs. And it sure seems like it will be too soon to do it all over again in 12 months from now.

I'm sure the answer that we will be getting is mainly because of the aluminum engine and the head problems these cars sometimes can have.

You mentioned that some of the cars you have owned were changed at 3 to 5 years. Up till last month, my newest car ever was a '72 (Chevy Impala). I've been owning old Chevys now for about 35 years and never once changed the coolant because of maintenance. Just when I was changing a water pump, radiator, etc and would think that the coolant looked a little old.

But I did learn in general and on here as well that these cars need different maintenance on them.

HUF,

I read where you partially change your coolant and if I'm correct, you are leaving about 2 1/2 quarts in there, but adding 6 new tabs everytime. I'm just wondering if thru the years, you would have a much higher sealant ratio than called for and wondering if that would be OK?
Well, the concentration of the sealant over years will increase if nothing happens (say, water pump going south lol). But, I am sure even 12 pellets are not going to hurt anything (say, plug the heater core). If I get that point I will probably empty the whole cooling system. Honestly I expect another 15-20.000 miles from my Seville and I do not think it's going to take more than a year or so... maybe two.
 

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Cadillac 1993 Deville 4.9, 1991 Eldorado Touring Coupe
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370 Posts
Discussion Starter #7
Thanks guys for the input! Thanks HUF for the pics and explanation and thanks GM fan for asking about the pellet concentration, I didnt think of that myself.

Right now i got a bigger problem on my hand with "Great White" I posted under the FWD Deville etc category as "This is so not good!"
 
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