: Coolant Change 98 Deville

04-09-05, 09:00 PM
I've scoured the threads here regarding coolant change I wanted to get some hints before I begin.

what happend was, developed a crack in the surge tank and coolant leaked out. Got a low coolant level warning, and I had no choice but to add the bottle of water I had with me. (I think i added about 500 ML, 16 Oz of regular bottled drinking water into the surge tank) it was dark so I couldnt check the level.

Anyways the warning went off, and I made it home. I didn;t want to spen 200$ on a new tank so I used AquaMend 2part epoxy. I thought it may not hold but damned if it did. Its been afew days and it hasn't leaked out at all. (I cleaned the area around it so I can see if it did leak)

Now that I have mixed water into the system I figured I better do a coolant change soon.

From what I read here this is what I need:

3 GM pellet/additives
2.5 gallons of DexCool 50/50

The procedure goes, remove cap from surge tank, put a pan capable of 2 gallons or more volume capacity, remove lower hose, let it drain, pop the tablets (no need to crush?) into the hose, re-attach hose.

With engine OFF, start to fill surge tank slowly and when fluid starts to fill up the tank, start the car and idle then rev up to 2000 rpm a few times.

Then with engine running add coolant mix until it comes up to 1-2 inches of the filler cap.

I am missing something, does this sound right? I don't want to run into surprises after I start.

Some questions, I can't get the surge tank filler cap off, it twists but doesnt come off. Any tricks? Just force it?

How much coolant should I buy? I read that in reality (unless you force out the remainder) you only get about 1.5 gallons of coolant out anyways just by pulling off the lower hose. Bbob, you mentioned its not critical to force out the last drop (do you think its cool even in my case, where I added straight water to the system....be it just a little bit)?

I don't have a big drain pan....thinking of going to a 99c shop to buy a plastic flat container of some kind......guessing a gallon OJ container or two aint gonna cut it? Any advice here?

Does it start gushing out all over? (anything I can do to keep it under control, avoid getting critical electronics wet?)

Thanks in advance!

PS My factory manual mentions removing surge tank, draining it, washing it out with soap etc etc.....necessary?? (do I need to think about changing the thermostat, replacing hoses while I am doing this?) its not leaking or anything.

98 deville 92000 miles on it. (bought the car at 64k miles, and I have never changed coolant yet)

04-10-05, 01:00 AM
Do yourself a favor and get a new surge tank. I have never seen one repaired that lived very long. There is really no adhesive that will stick to the plastic and when the system builds up pressure on the first warm day it will pop the repair off and leak again....stranding you farther from home this time in all likelyhood. Get a new tank......

To remove the surge tank pressure cap push down on it to get the locking tabs to clear the detents in the cap fitting. Loosen it and then push down on it while turning to remove completely.

Your system uses DexCool so make sure you get the correct type of coolant.

Premix the coolant 50/50 with distilled water. All you need to do is to drain the system at the hose like you describe. It will gush out pretty good if you just pop the hose off so have a large pan ready and a garden hose to flush away and dilute all the coolant you spill. Since there was a little water added to the system you might want to add an extra splash of straight coolant into the surge tank to compensate before refilling with the 50/50 mix.

Just pop the pellets into the hose...no need to crush or do anything dramatic.

Cleaning out the surge tank just gets any sediment or debris out of the tank. Since you are going to replace the tank anyway this is not a big deal.

Do NOT trust the epoxy repair as it WILL fail.

04-10-05, 02:44 AM
Thanks always Bbob!

so the epoxy's gonna let me down like a feared.......damned.

So I guess it makes sense to do both at the same time then.

I've been trying to locate the part number and the part but no luck. Where do you go to find part numbers? (I have the GMP/98-EKS-3 Service Maual....is it in here somewhere? BTW I find this thing very user unfriendly)

04-10-05, 04:13 AM
one more thing, bbob you posted 6 pellets on another thread but my service manual says 3. Your thoughts?

04-10-05, 08:10 PM
Personally I recommend 6 in the Northstar. Since the Northstar will not leak coolant into the oil in the event of a gasket failure the use of the supplement is mainly an insurance against nuisance external leaks. That is why the service procedure says only 3 pellets. 3 makes the coolant look less "dirty" and such but 6 will provide more protection against any leaks. 6 are spec'd for the 4.1/4.5/4.9 because the sealant is required to prevent any internal coolant leaks in the event of a gasket weakness or porosity or ??? so the requirement for sealing is much more necessary. Our testing showed that 6 pellets provides the maximum sealing protection.

04-20-05, 05:59 PM
Finally got the part number for the coolant tank from GMpartsdirect
its 3540041 radiator surge tank, includes coolant sensor.
about 40$.

Any suggestions about replacing the thermostat or the hoses while I'm doing this? (I wanna order all the parts in one shot if I can)

The hold up is, I dont have a ramp/or jack stands to get under there right now....any ideas?

04-20-05, 08:36 PM
The hold up is, I dont have a ramp/or jack stands to get under there right now....any ideas?

DO NOT USE CINDER BLOCKS Buy a set of ramps and/or jack stands as needed. They'll last you for the rest of your life. Cinder blocks will only shorten it.

04-20-05, 09:52 PM
The hold up is, I dont have a ramp/or jack stands to get under there right now....any ideas?

DO NOT USE CINDER BLOCKS Buy a set of ramps and/or jack stands as needed. They'll last you for the rest of your life. Cinder blocks will only shorten it.

LOL, yeah the thought of driving up on some lumber or blocks did occur to me but I dismissed it quick.

I used to have ramps but I found that the large overhang on the front made it impossible to drive up on them. (the lip spoiler would hit the ramp and push it away) Plus these things are huge and heavy, I dont have space for em right now.....I guess I have to go for jack stands.

04-21-05, 02:41 AM
You will never regret buying a good, sturdy pair of jackstands and will find that over a few years time you will have used them countless times. The security of knowing that your car isn't going to fall while you are underneath is priceless and they are really inexpensive. A good floorjack will also be a priceless asset.


04-21-05, 11:46 AM
LOL, yeah the thought of driving up on some lumber or blocks did occur to me but I dismissed it quick.

I used to have ramps but I found that the large overhang on the front made it impossible to drive up on them. (the lip spoiler would hit the ramp and push it away) Plus these things are huge and heavy, I dont have space for em right now.....I guess I have to go for jack stands.
Yeah, I have noticed that problem also. I think if you place a short length of 2X10 in front of the ramp to get the car a bit higher when you enter the ramp , that might get it high enough to clear the spoiler. I haven't tried that yet but will the next time I need the ramps.

04-24-05, 06:12 PM
Hello Powerglide, we are car twins.

I am curious to know how you knew that the surgetank had a leak? I understand that coolant can escape from many places.

We have not been using Dexcool, since we got the car a few months ago and we have a mysterious leak into nowhere.

Would draining, switching to Dexcool and adding these pellets possibly help our mystery problem anyone?


04-24-05, 06:19 PM
Hi avokshi,

My leak was from a tiny crack at the top of the surge tank, right where the hose attaches. I could see a hairline crack and also noticed residue/stain of coolant that had run out and evaporated.

I am pretty sure my car is running Dexcool (but I haven't checked yet). The pellets are designed to stop leaks so it may help your situation.

Look around the tank, and the lines running from the tank, around the radiator and hoses for a white stain/residue to see where the fluid is leaking from. If its a big enough leak, maybe you can get the car running warm on a hot day and look underneath and around the engine to see if you can see it dripping. If you see white vapor/smoke from your exhaust you may have coolant leaking inside....which is a bad sign.

I hope you find your leak, let us know...good luck.

04-25-05, 01:33 PM
Thanks Powerglide, I will be sure to check the above. One day I briefly saw white steam from the exhaust but another day there wasn't so I am not sure...

I will take pellets over a headgasket any day!

04-27-05, 04:18 PM
I dipped a piece of paper towel into the coolant tank to make sure it was pink/dexcool before buying a few gallons of it and found that the paper towel came out covered in black soot like residue. there was even a soft chunk of this residue stuck on the towel.

Is this normal?? Do I need to flush the whole system out?

(it says in the manual to flush the coolant tank out when doing a coolant change. It must be to remove this crap, but this is very disturbing)

05-18-05, 08:01 PM
My back hurts like hell......I finally did the coolant change and replaced the surge tank (reservoir).

It took me damned near 5 hours to get it all done. My hands are cramped and my back ......well I already mentioned it.

If I could go back in time, I would probably not have done this job myself......maybe.

Not counting the labor I put into it, I am out about 100 bucks in parts (this includes a pair of ramps and a drain pan so it could be thought of as 60 bucks in parts) The shop estimate for parts and labor was 200 bucks....so I save about 100-140 bucks....I guess not bad. But it was a serious pain in the ass.

Opening the petcock to drain the radiator=impossible to reach, very painful.

Getting the radiator hose disconnected and reconnected to add the supplement=pain in the back

Getting the surge tank disconnected from the lower hose=immensely difficult due to the tight space

Getting that same hose reconnected to the new tank=virtually impossible because of the damned hose clamp (not the type you tighten with a screw driver, they are the type that requires a set of pliers to compress the springs to loosen.....but theres not space in there to get pliers near them)

Not to mention removing the strut tower bars/battery cover plate/battery and all kinds of plastic shields and such.....holy moly.

I researched the heck out of the job prior to going in, and its all simple enough on paper, but in practice its a tough job to do if its your first time.

My hands have cramped but I needed to get this out......I am now gonna sit in the Jacuuzi, drink a beer and soak in the pride and satisfaction that only comes with getting this done (rather that giving up and having it towed to the mechanic....which I seriously considered as I spent almost 3 hours getting the friggin lower hose to go on the surge tank)

Thanks to everyone who helped me get ready for the job!

PS I ended up getting about little less than 2 gallons out of the system.....(total capacity is 2.5 gal), just an FYI if you are thinking about what size drain pan you need or how much coolant you should buy.

05-18-05, 10:31 PM
Powerglide, we salute you, nevertheless. I had a similar situ. to yours with my ex- 99 Deville about two or so years ago - I got the "low coolant" message one Saturday AM. I topped up the tank, and noticed that there was a fairly good sized crack where the line fed into the tank from the top of the engine - the fitting there does not look all that structurally sound, and the gradual flexing or whatnot over time ended up cracking it. The D was covered by a GMPP warranty at the time, so I just took it to the dealer. They ended up replacing the tank and the radiator. (And billing GM, I suppose..lol)

You're right though, there are more plastic shields, arcane twists and turns, and hidden connectors on the front end of a Caddy than almost anything I've ever seen. One of the first things I've done with all three of the ones I've owned so far is to remove all those nasty wire-spring hose clamps and replace with actual screw-driven ones, wherever I can see and get to them. I also make sure I can orient the screw so I can get to it with a regular slotted screwdriver.

Congrats on a job well done, and enjoy the well-earned rest. :)

05-19-05, 02:33 AM
Thanks Jim!

I'm still sore from all that work, plus I got a few scraped knuckles out of the deal too....

Funny my tank cracked in the same spot as yours, its gotta be a design problem, it sticks out and gets cyclically torqued till it cracks....I hope I never have to deal with that again.

And those wire-spring hose clamps are the worst!!!!!! The reason it took 3 hours to get it back on was because I tried everything from using zip-ties to keep the spings compressed to contortionist maneuvers involving all differnt kinds of tools.....in the end I snuck into my apartments' trash collection chute and ripped off the hose clamp from the garden hose and used that instead of the original ones. (I had different sized clamps but they were all too big or too small.....figures! Anyways, I replaced the one in the trash chute with one that I had)

BTW Bbob, you were right about the epoxy fix, when I cracked it open I saw that there was a small leak that had saturated the epoxy locally. Glad I changed it!

08-03-05, 08:29 PM
awwwwww crap.....now I look like a nut responding to invisible responses from Sal....when in fact I was exchanging useful info with mr B~!

08-03-05, 09:18 PM
We understand.