The van needs a coolant service, help!

[The Critic]

Hi,

My dad owns a 92 Toyota Previa, with 63,000 original miles. The vehicle has the original radiator hoses, thermostat, radiator, and radiator cap. The owner's manual recommends "Ethylene Glycol" coolant, mixed 50/50 with deionized or distilled water. There is no mention of a specific type of "Ethylene Glycol" coolant; the listed service interval is 3-yr/45k miles.

Although this vehicle shows no signs of cooling system problems, the cooling system maintenance has been neglected. The first coolant service was done in 1997 at a local shop using conventional 50/50 silicated coolant. In 2004 (at 45k miles), the local dealership did a coolant service. They drained both the radiator and the engine block and refilled with Toyota Red (not Super Long Life Pink), which is a 2-3 yr service life coolant.

The pressurized surge tank on the vehicle shows a minimal amount of crud in the coolant. I see some debris floating around in the fluid, which I suspect is some silicates that had previously fallen out of suspension. The color is reddish, a darker red. No rust from what I can tell.

I have access to a school shop, which has a RobinAir 75700 coolant exchange machine. The machine uses 80-120 psi of shop air to extract/fill the cooling system with the engine OFF. It connects to the upper radiator hose and the radiator.

As a result, I have several questions:

1. Since the owner's manual does not specify a specific type of coolant, only the generic "Ethylene Glycol" 50/50 mixture recommendation, is Prestone All Makes All Models coolant the correct coolant for this application? It’s only $9/gal at Walmart, so I’m planning to pick-up three gallons and three gallons of distilled water, along with the TBD cleaning additive.

2. Since the cooling system has not been serviced on time in the past and there is a minimal amount of buildup, which cleaning solution should I use? Would the Prestone Super Flush or the Super Radiator Cleaner be more appropriate? (Note: I'd like to minimize the potential of developing coolant leakage from this coolant service, if possible.)

3. The cooling system capacity on this vehicle is 12.2 quarts. After using the cooling system cleaner, I'm left with a system full of water, debris, and some leftover cleaning solution. The exchange machine only runs 50/50 coolant/water mixture through the system. How many quarts of 50/50 solution should I run through to ensure that I adequately replace all of the water and am left with a true 50/50 solution at the end?

4. For both cooling system cleaner products (Prestone Super Flush and Prestone Super Radiator Cleaner), the instructions state that I should drain the cleaning solution, refill with water and run the system for an additional 15 min prior to refilling with the correct concentration of coolant and water mixture. May I skip the "refill with water, and run system for additional time" phase since I am using a coolant machine that supposedly removes nearly all of the old fluid, compared to the inefficient methods most DIY mechanics use?

5. This vehicle has a remote pressurized surge tank. After exchanging the system with water, what is the best way to add the cleaning solution to the system? If I add it to the pressurized surge tank, how long will I need to run the vehicle, as I understand that adding the product to a pressurized surge tank will cause the solution to take much longer to circulate?

Thanks.

 

[eljefino]

That robot looks like a solution to a problem noone asked.

I would do it old school, drain the coolant you can, add clean water (if you live in CA desert cheapie bottled is probably best), run that for a day, drain that and measure it just for grins. Add 1 1/2 gallons of 100% antifreeze then top it off with water. There will be trace amounts of old antifreeze in there so you can underdo the 1.5 gallon mark slightly.

As for the pressurized surge tank, see if you can get that off the vehicle easily. Put in a teaspoon of automatic dish soap and fill it 1/3 with water. Cover its output nipples with your hands and shake... Other parts of the van you can get apart... like the hose to the heater core... take the hose off and stick a garden hose in there loosely to flush it... same with the radiator. Incidentally the 80 psi hype of that robot just runs the robot... it doesn't (shouldn't!) apply that air pressure to anything in the car.

That robot looks like something a quickie lube shop might use... wasting chemicals for no good reason, and getting an inferior changeout. Flushing with more antifreeze won't do as well as a two step process. Since you strike me as the kind of person who has time to do it right... leave the machine in its corner.

Incidentally walmart's store brand of antifreeze is extremely similar to the prestone you mention.

 

[The Critic]

I am planning to:

1. Exchange system with 5 gallons of water to remove old antifreeze.

2. Add chemical. Run for 30 min or several days depending on the one I use.

3. Hook up robot and run through 16-20 quarts of 50/50.

So I am going to do your two-step process, just with the robot instead. But should I use the chemicals at all to try and clean out the system? Which Prestone one should I use?

 

[Gary Allan]

I've used the expensive Prestone cleaner without problems. They're mild now and won't (allegedly) harm any of the internals ..just the scale

I was a chronic cooling system neglector on most of my vehicles (pre-jeeps) and I'm pretty sure that I have the original OEM lower rad hose. The others have been replaced at failure. I've had to replace the rad in the minivan once about 20k ago due to seam leakage (plastic tanks)..probably about 10 years/150 miles (+/-). One thing that may have really cost me was the head gaskets externally leaking. This was probably a result of my neglect ..again ..it took over a decade and about 165k. It may be something to bring up to your father and have him ponder the avoided costs. This was something that just dawned on me when a fellow member mentioned how he didn't think all that much about head gasket failures in aluminum head/cast iron block hybrids.

FWIW- I use LowTox in everything. My jeeps appear to have the most crud that I've ever seen with vehicles that new. I replaced one radiator preemptively with a 3 core copper/brass. The OEM junk is a single core aluminum. I'll pray that the heater core (same OEM junk) doesn't let go for a very long time.

 

[unDummy]

This is pretty simple.
Drain/refill your radiator with ANY 50:50(or mix your own).
Then remove that plastic surge bottle and clean it out. Some people use rock salt or gravel to shake clean the overflow, recovery, or pressure bottles.
Then, toss in a bottle of RMI-25 or Schaeffers clean&cool.

See how simple that was?
No machines, no flush chemicals requiring multiple rinses, no screwed up water:coolant ratios caused by using garden hose flush kits, no fancy robot needed, no thinking required......

Drive for 6 months. Replace the thermostat, rad cap, all hoses, and refill with the same 50:50 antifreeze you used before. Start a yearly rad drain/refill with that same antifreeze.

 

[Shelby]

Critic is a non believer of cooling system additives. It doesn't matter that those Prestone flushes are harsh toxic materials that say not to leave in the system too long becasue they can damage it, plus add that RMI25 is a non toxic effective cleaner, it sounds to good for the C man. RMI25 are for those of us who prefer not to be complicated, lol BTW, the Prestone flush cleans nothing. I used it first (twice) before I tried RMI25 for the first time, and RMI25 deposited all kinds of grime into the overflow tank. Obviously the flush didn't get the junk. In fact I even left it in the tank overnight, and the Prestone flush didn't remove any gunk.

 

[The Critic]

Shelby, I'd use RMI25. If and only if I could buy it at Walmart and it wasn't so expensive.

 

[Shelby]

 

[The Critic]

Right now, I'm leaning towards the following:

1. Run 5 gallons of tap water through the system.

2. Add full bottle of Prestone Super Radiator Cleaner

3. Drive for a week.

4. Run additional 5 gallons of water through.

5. Pull radiator peacock and add 6 quarts of concentrate.

Then I'll probably drain and refill on a more regular basis. Now only if my father will let me replace those 15 year old radiator hoses.

Where's Mr. Ray?

 

[unDummy]

I would never run tap water through a system. Sorry, but I don't want those minerals or chemicals entering my coolant. Some minerals might settle out and cause the problems that you are trying to prevent. Some tap water chemicals will create the corrosion that you want to prevent or remove.
I would never run straight water for a week. Without any protection from corrosion, you're just creating rust. Some people wonder why they can't get their cooling system clean. Its because they are causing the problems by running straight tap water with corrosive flush chemicals. Duh, splash some water on your brake rotors. Don't they rust overnight? And, you want the insides of your motor(assuming iron block) to rust everyday for a week with the superflush in it? If you have a aluminum head+iron block, think electrolysis.

Your water pump will also thank you for the lack of lubrication. And, rusted crud is not too friendly on water pump seals and impellers. Budget that WP for the future replacement.

Unless you have the means to remove all that tap water and flush product, some will always be left behind. Do you plan on running 20 gallons of distilled water to rinse out all that problem rust water and flush stuff. I doubt it. What about all the rust left behind coating the internals that is created by not using protective coolant for that week? It ain't going anywhere and will give your new antifreeze an instant workout aging it quickly!

Will you make the effort to calculate the correct ratio of antifreeze or vacuum the block dry? Sorry, but every back yard mechanic that uses the garden hose ends up with 25% ratio and wonders why their coolant goes bad quickly or freezes in the winter. Too many forget the capacity of the straight water in the block and just add the 50:50 to the water already leftover in the system. Block drains aren't always easily accessible and are also often ignored. So are the heater cores and other inaccessible coolant reservoirs that are forgotten when calculating ratio.

There are times when some will just have to accept additives because that, which is commonly available, just doesn't work as well as we hope to.

And, since cost was mentioned. A $14 bottle of Schaeffers-#258 or $20 bottle RMI25 saves a ton of time. What do you value more? 20 hours of your time playing around with your flush method. Or, a simple rad drain/refill, antifreeze bottle cleaning, and top off with 'additive', which all together will take an hour at the most, won't screw up your ratio, won't add rust to your system, won't add caustic or corrosive chemicals..... $20 or 20 hours, I'm worth more then ~$1 an hour!

And, if you do use the Prestone Super flush or any other product from Gunk, Zerex or Prestone, please follow the directions. Don't not deviate at all; no 5 gallons of tap water, time the motor hourly and not blindly run for a week, simple couple drain/refills....

 

[Tempest]

I was able to get 32 oz. of RMI-25 for 4 = 8 doses. 25/8 = $3.125 per dose. That's not a lot of difference in cost from the quick Prestone Flush, and is cheaper than the long flush. Plus, you can use it as a maintenance chemical like AutoRX, and don't have to drain it like Undummy said.

 

[Drew99GT]

I wouldn't run pure water for that long; no lubrication for the water pump. unDummy is smart!

 

[Drew99GT]

If there is no visible scale, why screw with flushes and machines? Take the thermostat out after draining the system and getting yourself a ton of distilled water. Reinstall the thermostat housing, fill the rad with distilled water, start the motor, undo the petcock, and idle flush with distilled water for a couple minutes until clean distilled water drains away. Stop the motor, reinstall the stat (point of stat removal is full flow through the system), close petcock, find out what 1/2 the volume of the cooling system is, add that amount of full 100% antifreeze concentrate (not 50/50), top off with distilled water and be done with it. Peak Global Lifetime can be had from Walmart, and the van will likely be in a scrap yard before the procedure ever needs to be done again.

 

[Ray H]

Quote:

---

I would never run tap water through a system. Sorry, but I don't want those minerals or chemicals entering my coolant.

---

Right, freakin' on! Calcium-laden hard water promotes scale formation. Mineral sodium salt-laden residential softened water promotes metal corrosion. Predictably, neither result is desirable inside a cooling system. (Contrary to urban myth, aluminum engine components exposed to coolant will readily corrode in the presence of mineral sodium salts. (The hydrates of organic acid sodium salts used in long life coolants such as DEX-COOL are an entirely different matter.) Aluminum Oxide (AL2O3) in its various states of purity, also known as corundum, an industrail abrasive, and the gemstones, ruby and sapphire, is the second hardest naturally occurring mineral after diamond. It shouldn't take a brainiac to understand that small particulates of this stuff circulating in the coolant will destroy waterpump seals. NEVER use residential softened water to refill a cooling system.)

 

[Ray H]

Quote:

---

I wouldn't run pure water for that long; no lubrication for the water pump.

---

Waterpumps use pressed-in, sealed, prelubricated bearings. Waterpump bearing seals are subject to wear, though - and once compromised, will lead to bearing failure as coolant contamination compromises the lubricant.

 

[Drew99GT]

Ray, I think that's about the 3rd time you've reminded me of that!

 

[The Critic]

Thanks for all the replies.

To address a few points that have been brought up:

1. Yes, there is scale and debris floating around in the existing coolant. A lot of it. I just checked tonight. It doesn't look good at all.

2. The mid-engine Previa is too difficult to fuss with the T-Stat. I don't have time for that. Heck, that van might hit the wrecking yard a few years from now for some other odd reason...who knows.

3. I agree with the distilled water. And I do plan to run 20 quarts through the system (via machine) to remove as much chemical as possible. About this distilled water though. This system has been seriously neglected. The coolant has been changed at 2-3x the scheduled interval, and each time using conventional coolant and tap water. Much damage has already been done. Even with the cleaner and careful flushing, I doubt I can bring the system back to good condition...so I'm not sure how much benefit distilled water will have here. Of course, if I started with a properly functioning system in the first place, then I would of course only use distilled water by all means.

4. Tap water is fine per Prestone. Per Texaco. And I wonder if GM uses it as factory fill as well, since their owner's manuals make no mention of requiring distilled water...only clean, drinkable water.

5. Oh, and I'll definitely add the correct amount of concentrate to ensure that I obtain a 50% concentration of antifreeze. The system is 12.2 quarts, so I'll add 6.25 qts of concentrate. Problem solved.

6. Looking in the ingredients of the Super Radiator Cleaner, apparently the additive contains ingredients that provide metal protection after some discussion with Pabs.

As a side note, earlier today, I picked up two gallons of Prestone All Makes All Models fluid from Wallyworld at a little under $9.00/gal. There is also a $5 gas card offer with the purchase of two gallons, bringing the total cost down to a little over $6.00/gal. I also purchased a container of Prestone Super Radiator Cleaner for a bit under $5.00.

 

[m2200b]

1. Before you have use tap water go online and check your water district. They will usually post your water and its hardness - some in CA is fine - other is trouble and its easy to be informed.

2.I'd just drain and replace with distilled and your choice of pure coolant. Then I'd do the same again in 1 year. The new coolant has a good mix of additives to fix most problems. You can change sooner if you really are trying to get closer to 100% new .

3. your vehicle's history doesn't sound too bad and toyota's radiators are pretty stout compared to honda and some other that usually fail.

4. i'd replace the big hoses and those to the tstat if you don't see hose replacement on the toyota 2004 work order. You can put the rest of the hoses like those to the heater on the next change list.

 

[m2200b]

I'd add change the tstat, radiator cap and all the hoses after seeing its a 1992.