Coolant Flush

[jptrsn]

Hi everyone,

Newb here, so forgive the questions... I've already searched, and found some answers here, but I wanted to get a variety of opinions before I make my final decision.

I have a 2003 Buick Rendezvous 3.4l V6 (from what I've read, it's the LA1 engine) with 135 000 km on it (that's about 85 000 miles).

I noticed a very slow coolant leak (a few drops on the underside, but not enough to make a puddle in my garage). I decided to flush the coolant system, and maybe use a stop leak (like Barr's or Prestone), and looked into it a bit more. Much to my surprise, I found out a lot about dexcool, and now I'm all nervous about my engine. I don't have any evidence of sludging in my cooling system, but I haven't really looked all that closely.

Basically, I've decided to do a complete flush, and refill it with Prestone (even though it's ethylene glycol, too). I can't seem to find the green coolant anywhere, and propylene glycol seems to be difficult to find, too. Basically, I'm going with Prestone because it's what my father-in-law used to use, and I don't know any better. I could also use a store brand, or Peak, or even dexcool again (although I'd rather not).

However, when looking through my service manual, it says a few different things. Now I'm getting all confused...

Under general coolant system flush, it recommends to use a flush kit (like the Prestone Flush 'n Fill), but I'm hesitant to cut open a heater hose. It also mentions that I need to turn the heater control to full hot.

Under the cooling system section, it lists instructions where you drain the radiator and the engine block, and fill it with water. It also instructs me to remove the thermostat (which the other section neglected to mention). It doesn't mention a flush kit or the heater control. I then have to run the engine with only water in it for 20 minutes, then drain and fill again and again until there's no trace of coolant. Then, I can drain the system a final time, add half the coolant capacity of the engine worth of concentrated coolant, then top it off with distilled water.

Which one do I listen to? I had originally planned to follow the cooling system instructions, but I'm not sure which one is right. Do I need to pull the thermostat and replace it every time I drain the system? It's kind of a PITA because I have to remove the exhaust crossover pipe to get to the thermostat.

This is my first cooling system maintenance, so I'm a bit nervous. Please weigh in with your opinion.

1) Do I need to pull the thermostat to flush my cooling system?
2) If I've already pulled the thermostat, should I just go ahead and replace it? What's the life-expectancy on a thermostat?
3) Should I flush using the flush kit, or just drain the block and rad?
4) Is there any danger in using a stop leak product?
5) Should I use a chemical flush, or is that a really bad idea?
6) Is there any particular brand of coolant that you recommend? What base is it?

Sorry for the long post, but I'm full of questions. Thanks for the help!

[pmaniac69]

best way to flush a system for the home mechanic, drain your fluid out from the radiator, fill the system with water, let it run for the 20 minutes that you mentioned, then let it cool, and drain again, but this time (I might get bashed a bit for this) after it has drained from the radiator, leave the petcock from the radiator OPEN, and start the engine again for a while so the water pump will pull the rest of everything out've the system, but keep your eye on the temp gauge!!

thermostat, since you got it out, might as well replace it

IMO with the stock gaskets and dexcool being in the system, I would not use any type of coolant flush aid, just water, and I would put dexcool back in the motor as well.

I don't like dexcool one bit, but since you have not done you LIM gasket yet, I would not put the old fashioned green stuff in it yet

[jptrsn]

Thanks for the advice.

I'm still in the planning stages, but I've been looking more closely at the engine, and I found the coolant leak!

It seems to be coming from the thermostat housing gasket, which I have to replace when I do the thermostat replacement. But I can't seem to find the part!

Does anyone have a part number? I found one part - it's labeled as a thermostat housing o-ring - but I think it's actually the thermostat o-ring. It's made by Gates, part number W0133-1681977

I thought that the housing required a gasket, not an o-ring. Is this right? Part numbers, anyone?

Thanks!

[abycat]

hey guys one of my jobs is a tech at mr lube. we have a way to flush rads that works so good its crazy. we first fill the rad with clean flow rad flush and run it for 5-7 min. it has to warm up and the thermostat has to open. and the heater has to be set to defrost. doesnt have to have the fan on but has to be on defrost to open the heater core valve if equipped. then the upper rad hose is disconnected and two hoses are connected to the fluid exchange machine that forces the new coolant that doesnt mix with the old because hot and cold antifreeze doesnt mix. the machine has two compartments one for old and one for new. the coolant is introduced through the top rad hose with air pressure matched with the cooling system pressure, and the old coolant is pumped into the machine. The rep did a test with just water and a water sample was pulled from the machine and you could have drank it it was pure water truly amazing and it takes 15 minutes from start to finish on a god day with a good tech 22-25 min at the most. the fluid in the coolant overflow is sucked out with the evac and replaced with new. now to do that process without the machine just empty the coolant by hand from the rad and block and syphon the coolant out of the overflow and refil with new. I would not put sealant into it unless it was from kleen flow. the gasket could probably be replaced by you pretty easily. but please turn the heater to defrost to open the heater core, we do it to all vehicles, from big dodge deisels to your same car. Now for your dex it is dead it has a life of 6 years or 160,000 KM.
i would put dex back in because you will probably sell it before you have to do it again. but if you dont make sure your coolant you get is approved for use in aluminum engines. by the way coolant doesent get a worse freeze point protection when it gets older it actually gets more acidic as it gets older. around a ph of 8 its damn close to being bad. it will eventually attack the metals and eat your engine away. dex starts off almost acidic but lasts for a long time. hope this helps good luck.

[jptrsn]

I called a Buick parts counter, and they informed me that the thermostat housing doesn't have its own gasket: it uses the o-ring that comes with the thermostat. So, my plan is:

1) Drain the dexcool.
2) Pull the thermostat, take out the coolant plugs in the block, and flush the cooling system with drinking water.
3) Put in a new thermostat, which I'm hoping will address the leak.
4) Fill the system with plain ol' water, and idle the engine for a little while.
5) Drain the system again (but this time, I won't pull the plugs in the block or the thermostat - I'll just drain the rad).
6) Fill the system half-full with a Prestone ethylene-glycol coolant. Half capacity is a little over 4L (so that means I have to buy two jugs of coolant, and use 1 and a little bit from the second one.)
7) Top off the system with de-ionized water.
Let the air bleed out of the system.
9) Run the system for a few minutes, then top it off with a 50-50 water/prestone mix.
10) Check the levels over the next few days and weeks often, topping off the system with more of the 50/50 mix.

Anyone see any major problems with this? By my best guess, it'll be about $65 (Canadian) and probably about 5 hours to get everything done (I work slowly). Right now, I've decided to forget the flush kit, but I might change my mind yet again.

Thanks for any advice!

[asylummotorsports]

You should be pulling the LIM and fixing what is a KNOWN PROBLEM on those engines that is only going to get worse! And it gets worse fast!

And using Bars Leak will only compound the problem and create more of it's own.

Do it right or you'll be doing it in the middle of winter.

[pmaniac69]

I was thinking the same thing asylum, if its leaking around the thermostat housing, I would REALLY be weary on the LIM leaking

and if it is leaking, that prestone cooling system cleaner will probably just make it WORSE

[jptrsn]

I've checked out the procedures for replacing the LIM gaskets, and it looks like it's a bit above my pay-grade, so to speak. Since this is my only vehicle, I have no public transportation available, and my wife is almost ready to deliver our second daughter, I think that I'll hold off on the LIM for now. I haven't seen any evidence of coolant entering either the cylinder or the oil, so I'll keep an eye on the temperatures, the oil, and the exhaust. If need be, I'll end up taking it to the garage to get the LIM gaskets replaced (which will make me unhappy, but ensure that I'll keep my family mobile).

In the end, I've decided against using either Bar's leaks, or a cleaner. I'm just planning to flush with clean water, and replace the thermostat to address the leak. The prestone I'm referring to is their ethylene-glycol based coolant, which I plan to use instead of dexcool. I can't see an issue with this, because they're both e.g. based, and supposedly, the prestone can mix with any other product (so it should be okay to mix with whatever traces of dexcool remain in the system after flushing).

My question is: should I use a flush kit (you know, the little fitting that you splice into the rad hose), or would it be sufficient to flush it by filling and draining with clean water? I've checked the overflow pipe, and there's a bit of crud in there, so I think the flush is really necessary, but it'll be chemical-free.

I know, I know, I really ought to do the LIM gaskets... This is my first time actually getting into anything serious in the engine - all my previous experience is either in suspension, body/trim, and I've done the O2 sensor - all stuff that won't kill the car if I mess it up. I'm a bit more wary of getting into the engine up to my elbows. Plus, I don't have any buddies who have done this kind of thing, so I'd be totally on my own.

Thanks for the advice, guys. I really appreciate the recommendations. I'm just afraid to pull the throttle body, upper intake manifold, fuel rails, and lower intake manifold to get at those gaskets. Chances are, I'd miss a drop of RTV or something, and I'd end up killing the engine.

Thanks again. I'll take photos along the way, and post the results once I've done the work.