1999 T&C Minivan Rear Heater Core

You should be able to see from the fluid trail if it's coming from within the passenger compartment or just at the hose joint.

My recommendation is to disconnect the 2 hoses going to the rear heater and couple them together, bypassing the core. If the leak goes away then you know it's the core.

If the core is leaking your best bet is replacing it I think. You can get a radiator shop to resolder the inlet tubes but their labor would cost what a new core would. I wouldn't recommend JB Weld on a joint that is in the passenger compartment, in order to properly apply it anyway your going to have to take the interior panel off to get at the heater core and by the time you get that far you might as well replace the core.

Personally I think the 5 year change mix is snake oil and in another 10 years when we see a lot of used cars with rotted-out cooling systems people will figure that one out. If your asking for advice on jury-rigging you may as well know that a simple dump and replace of the mix in the radiator will get about 1/2 of what is in there, and if you do that every

2 years you will likely keep the anti-corrosion additive package adequately supplied. Lots and lots of people have gone for extended change intervals with the traditional green stuff mainly due to lackadasical maintainence and have suffered no ill effects.

Flushing - if done properly (ie: backflushing) - gets rid of sediment that builds up. Just because you can make an anti-corrosion additive package last twice as long doesen't mean that sediment isn't still building up in the system at the same rate. There is always material loss from the materials (ie: hoses) as well as some oxidization - the cooling system isn't sealed - even though it may be happening at a lower rate - that all contributes material that settles out of the system into the nooks and crannies. I'm not convinced that the G-5 formulation reduces the rate that this happens at. Getting the chemical package to last longer is the easy part.

Ted

Ted,

Thanks much for your thoughts. By the way, I do realize I could completely bypass the heater core and eliminate the leak, but would like to retain the rear heater if possible since winters here in Chicago can be cold. From brief visual inspection, the leak seems to be coming from outside the passenger compartment, but as you suggest it will likely need to be opened up to confirm that. If I go to that trouble, then I may just elect to replace the heater core completely since it is now going on 10 years old. If anyone has replaced the rear heater core and can provide advice/comments on difficulty of that job, it also would be appreciated.

On the G-05, I've been operating thus far on a 4-year and roughly 40K mile cycle on my other vehicles and have not had any problems yet, so that is why I asked. For the record, I do the complete Prestone chemical flush (drain coolant, fill with tap water, add chemical, bring to operating temperature, then drain), then backflush afterward with a garden hose, then refill with tap water and bring back up to operating temperature twice to rinse the chemical, before refilling. The real issue here is time for the vehicle to cool down between each of these fills/drains, so as you can see it takes considerable time. Since I do this now with the 2-year stuff too, I was looking to save half my labor by going to the 4-year cycle with G-05.

To clarify my original question, I want to know if anyone is aware of anything in the chemical composition of the Zerex G-05 that is incompatible with the 1999 3.8L engine design (water pump, block, heads, TStat, hoses, radiator, heater cores, etc.) since the owner's manual specifies the use of green, 2-year ethylene glycol. Again, thanks for taking time to reply with your thoughts and suggestions.

Bob

Hi Bob if you don't really want to replace the core you can try K&W block sealer,I am a mechanic that has worked for used car lots for too many years but this stuff will work better than anything I have tried. You will need to drain the cooling system and flush with water and just follow directions on the can. You might have to look around to find it or "google it" I hope this will help. Ken

Ken,

Thanks for the thought, but I am extremely reluctant to use any type of cooling system sealer/additive. My thinking here is that anything intended to plug small leaks could only serve to reduce cooling by clogging the same radiator vanes and engine block/head passages that I have worked hard over the years to keep flushed and clear.

Bob

It should be a lot easier to replace the rear heater core than the front and I wouldn't hesitate.

advice/comments

I have had the panels in my van off - it's a different year than yours. You really want the factory service manual to know where all the hidden screws are. Alternatively, visit a local pick-a-part wrecking yard and go inspect the same year van as yours that has already been torn apart.

temperature,

You don't need to chemical flush if your regularly changing the coolant.

I have mixed feelings on the flush chemicals. The one time I went to the trouble to do it I ended up with a block worse off than before. (It hadn't had a coolant change in at least 10 years) My feeling on it is that if your regularly maintaining antifreeze then you don't need it, and if you do need it then likely your going to create a large slough-off of sediment all at once which will plug block metering passages.

incompatible

The original rule of thumb was that any American vehicle with an older copper/brass radiator and heater core, soldered together, should use old-style green ethlyne glycol for greatest protection against material loss on the solder. Original HOAT coolants (ie: Zerex G-05) did have some additives that protect copper and tin/lead solder, but not as much as the green stuff contained.

Use of Dexcool in these cars is known to plug heater cores, both Ford and Chrysler had a lot of problems with this when Dexcool (OAT) came out as OAT coolants rapidly corrode the solder. Dexcool in particular is known to turn corrosive in the presense of air, and is known to be damaging to many rubber seal materials - it should NEVER be used in a car that didn't have it as factory fill.

The story going around is that GM got environmental credits from the Feds for using OAT coolants, and so they didn't give a rat's-ass about what everyone else was using or how bad their own crappy coolant would be in other manufacturer's cars.

Older Japanese cars are also known to be safe with green coolant, regardless of what their factory fill was.

However, these days the original HOAT coolants have been reformulated with proprietary trade-secret chemicals to produce the newer "universal style" HOAT. In other words, the Zerex G-05 coolant of 6 years ago is not the same chemical as the Zerex G-05 of today that is marked "Universal" There simply isn't enough ancedotal evidence that today's Universal HOAT (G-05 or equivalent) is bad in older cars because these haven't been on the market long enough. So in answer to your question - nobody really knows. Zerex almost certainly will tell you that their Universal G-05 will be safe. But how long has it been on the market in it's current formulation?

Green coolant is held by many to be damaging to plastic radiators.

Green coolant is also more corrosive to aluminum radiator and heater cores and to aluminum engine parts.

However, like the Universal HOAT, there's now Universal green stuff on the market that has -also- been reformulated with trade-secret chemicals that are not supposed to be as corrosive to aluminum as before.

Newer American and Japanese cars use aluminum radiators and heater cores. They are safe for HOAT coolants (ie: Zerex G-O5) as a general rule.

There are a variety of European and Japanese coolants that are factory fill in their respective models (ie: BMW uses a blue coolant) these should NEVER be used in any models other than what they shipped in. The Japanese cars that these coolants come in are as a general rule safe for HOAT coolants. Not so for the European cars, which may or may not be, depending on the model. Worse from the European side is that there have been a number of changes from year to year in the proprietary cooants, making some not even compatible with each other for topping off.

As a general rule, only HOAT and original green are safe in a 50/50 mix with hard tap water. None of the specialty Japanese and European coolants OR the OAT coolants should be mixed with anything other than distilled water.

Different coolant types should NEVER be mixed. You must completely flush to switch from, for example, specialty Japanese to G-05, or from green to HOAT.

Ted

Ted, I'm a big proponent of HOAT/G-05. Where did you learn that HOAT has been reformulated? Can you provide links to any articles?

Also I have not seen any Zerex references to it being universal - that doesn't mean there aren't any - I just haven't seen any. On this page of their site:

say "There is no 'one size fits all' chemistry that is approved for use in all vehicles. Don't take chances?use Zerex AutoMaker Approved Chemistry" - that's above the pictures of their 3 antifreeze products - traditional green, G-05 and DexCool?. And on this page: don't see any suggestion of universal use, though I did put it in my wife's '99 Buick about 3 years ago with no ill effects so far. On this page: "Perhaps one of the most important aspects to look for when next shopping for antifreeze/coolant is approval from the maker of your car. Currently, there is no 'one size fits all' solution that is approved for use in newer cars. And filling your cooling system with the wrong solution may result in serious adverse effects.

"Products marked APPROVED have been subjected to years of field and lab testing by your car's manufacturer and are certain to provide the best performance and protection. Also, use of these products will ensure your car's warranty remains intact. The same cannot be said for using non-approved products, which may end up causing more problems than they solve. Some quality antifreeze/coolant producers even print the makes that have approved their products for use. This is always the best way to go."

Ted,

As always, you are a wealth of information. Thanks. Based on your response, you appear to be suggesting that I replace the rear core (thanks for the idea of visiting a salvage yard to "learn") and then stick with the green or go to the universal green stuff and just reduce my flush interval to reduce labor/time for the operation. I can accept that as an alternative I had not considered.

I will comment though on your line that HOAT coolant should never be mixed with tap water. This is pretty much an impossible requirement if you use tap to back flush, since you can NEVER get all of this out before you refill with coolant and distilled (like I do). I actually do my last rinse after flushing with distilled to improve the mix percentage of distilled, but this is still not perfect.

Also, I will say that even when I chemically flush and then back flush every two years, I get a good deal of brackish, brown water out of the system before it runs clear again. I assume this is normal, but this is why I have done it regularly at 2 year intervals. I can see the value with my own eyes.

Lastly, I'll add that I've heard and read so much negative press on DexCool that I have never ever consider using it.

Thanks again. Now for some good weather and a weekend to take this on.

Bob

Do you have an air compressor? You can get a cheap one from Harbor Freight for $80. When I flush my van, after rinsing with tap water I use an air blow gun and flush with compressed air. THAT does get most everything out.

Fortunately where I live we have extremely soft water - so soft, in fact that the water bureau has to put a chemical in it to harden it up a bit - otherwise it leaches an unacceptably high amount of lead out of copper sweat joints and brass fixtures.

If your seeing brown water in the initial flush BEFORE you are putting the chemical flush in, then I would consider that abnormal. I've not seen brown water out of any cooling system in any of the cars I've owned when I flushed them unless the cooling system had been neglected. I use green stuff with tap water, my vehicles are not as new as yours.

It's standard-issue for GM. Of course, GM also has the battery terminals on the side too. I guess they just like being different.

Ted

Ted,

Yes, I have a compressor. I never thought of using it for this purpose though. I guess that you must remove one of the heater hoses and attach it there to get that to drain out. I'll give it a try next time around. Thanks again for the ideas.

By the way, the rear leak turned out to be a bad connector hose. No matter how tight I tried to tighten the hose clamp, it never stopped the slight drip, so I cut new 5/8" heater hoses and made them slightly longer this time around, then just replaced them and re-used the same 4 hose clamps. For now, anyway, the dripping has stopped. The good news is that the heater core and the quick connections to it look fine ... the leak was on the other side of the hose connection.

Bob

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Yo - Ted - you there?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

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Yes, this news server I'm using isn't always, though.

Ted