Coolant filter- an experiment

[onion]

This thread is going to document an experiment that I'm trying, for a quick, cheap, and dirty method of adding a coolant filter in an automotive application. I'm aware of the spin-on filters- I deal with them all the time at work. But those are entirely too expensive and require too much under-hood room and ambition on my part. I just don't think that any marginal benefits would be worth the trouble, especially on my 16-year-old beater.

So the other day I saw a clear plastic fuel filter at walmart- with 5/16" hose barbs, which is exactly what I need for my tired old '94 Corsica. This car is well-maintained, but has had a hard life. This was the wife's car when I met her- at the time, it had 80,000 miles and the cooling system was thoroughly sludged by the Dexcool that somebody had converted it to (this car originally came with green coolant, but had some nasty, muddy-looking Dexcool in it by the time I showed up). Long story, but I had the radiator rodded out (this was in maybe 2001), and over the past 9 years the cooling system has been opened up several more times for various reasons (occasional leaks, intake gaskets, etc.). It's been flushed several times and I switched first to conventional green coolant in 2001, then to G05 around 2003. These days the coolant is nice and translucent and the car cools very well- but all these years later there are STILL visible remains of the DexSludge left in the cooling system. All coolant passages and the internals of all hoses are lined with a thin, brown, muddy coating. Even when a new hose is installed, it will be covered inside with this gunk next time I have the cooling system apart. So there should be no shortage of particles for this filter to strain out.

Here are pictures of the filter I used, it its original box and installed:

This car is driven hard and put up wet. It gets several short trips per day- usually between 2 and 9 miles depending on where I'm going. Right now it has 179,000 miles. I set aside some pliers, a couple of spare clamps, a 5/16" hose splice, some coolant, and some water- just in case this experiment fails catastrophically in the 100+ degree heat we've been having lately. I'll post updates as the experiment progresses, and maybe a new picture or two if there are visible changes.

I realize that the glue used in this filter may be water-soluble... the thing may just come apart internally. I'm quite sure that this filter can withstand the 15 psi pressure, but it might not deal well with the heat. We'll see. But I think an old beater like this with a known dirty cooling system (and a fairly new and functioning pressure cap) is a good test vehicle. If it works well, I might do something similar on the wife's car.



Edit: I see that the installed picture has a glare problem. I'll try to get a better picture before putting any miles on it.

 

[daman]

What hose is that the bypass to the intake? or the over flow?

 

[onion]

Here's a picture with slightly less glare.

Some of you may note that the coolant is green- and that I said this car has G05. When I initially switched to GO5 around 2003, I wasn't aware that the John Deere Coolgard coolant that I had filled with WAS G05. But it is... and it's green. Right now the car has some unknown mix of John Deere Coolgard and Zerex G05. That's why it's light green.

 

[daman]

So it's the over flow?

 

[onion]

I should have been more clear. The line that I spliced into is the air bleed line that goes from the top of the radiator to the pressurized coolant reservoir. With the engine running, it constantly flows a stream of coolant from the radiator into the reservoir. The plastic hose connection in the coolant tank is reinforced with a brass insert that necks it down to about 3/16"- so it isn't a huge amount of flow, but it's constant.

Lots of heavy trucks with much larger cooling systems (10-12 gallons) use 3/8 coolant hose for their coolant filters. So I think that this 5/16" hose should be adequate for my 2-3 gallon cooling system.

 

[engineerscott]

If that's filter is going to the overflow, I see an issue. When the engine heats up coolant will be forced forward through the filter and presumably particles will be trapped by the filter media. All well and good. However, when the engine is shut off the flow will reverse and the coolant will move from the overflow back to the radiator. In this mode, particles trapped in the media will be flushed back to the radiator. The basic issue here is that there is bidirectional flow, which doesn't lend itself to putting an inline filter in the system. Now if this filter is someplace else this may all be moot.

*** Edit - I see that this filter is not in the overflow path, so aside from the concerns you are aware of (heat and water effects on the filter) I think you are good ***

 

[mechanicx]

Engineerscott makes a good point. I think though that this hose goes to the top of the reservoir and drains down into it. And the bottom hose on the reservoir handles most of the reservoir backflow. I think some lesser amount of coolant can/will back flow through this top hose. I don't know if it will back flush the filter or not, but I'd assume some. I'm not sure what other convenient place you could put a cooler filter besides one of the heater lines. Edit: I posted before I saw engineerscotts edit.

 

[onion]

For what it's worth, I think that a coolant filter would be of less benefit in a cooling system with a non-pressurized overflow tank- as the overflow tank allows solids to settle out before the coolant is sucked back into the radiator. The wife's Lumina has such a setup, and little particles of crud will gradually build up in the bottom of the overflow tank- so I rinse it out every year or two.

But in this case the coolant reservoir is pressurized... little chance for crud to settle out.

 

[Propflux01]

Are you not worried about the plastic simply getting too hot and melting?

 

[onion]

Sure, it's a concern. That's why I've thrown a few extra supplies in the trunk just in case. But then again, this IS a gasoline filter, and seeings how it's designed to hold a highly flammable fluid under pressure- possibly under the hood- I suspect that this filter should be designed to withstand reasonably high temperatures.

I drove the car a fair amount yesterday and checked the filter several times. The plastic didn't become soft even though the ambient temp was well into the 90's, the engine was fully warmed up, and I was running the a/c. I think it'll hold just fine.

Not sure how long it'll take, but once some visible crud accumulates, I'll probably cut the thing open and examine whether or not the glue and filter paper held together.

 

[Gary Allan]

I can see the appeal of the visual crud check, but I can see that acrylic shell getting quite soft and have its pressure rating substantially degraded. Now it is made to withstand under hood temps, but the pressure component kinda trumps that.

..but you know all that and you appear to have prepared for that potential failure. I was just trying to figure out a safer way to achieve your goal.

 

[TurboWagon]

I really like this idea and your implementation of it. Let us know how it turns out in the coming weeks with the heat. I'd really like to do something like this on my car, but with the mountain drives I do, having it fail isn't an option!

 

[onion]

Yeah, a metal inline filter would be a safer option. I chose this plastic one so that I could keep an eye on it- in case the glue and/or paper comes apart. But if this one holds up (and I think it will), then I might try a metal inline filter- and probably stick with the same brand on the assumption that they'd likely use the same glue and filter paper that I tested with the plastic filter.

I'd get no feedback until I cut the metal filter open... but yes, it would be safer. Although I don't think this plastic filter is going to cause any problem. No warning signs so far.

Update: The filter paper has already turned a satisfying muddy brown color from the remaining 10-year-old DexSludge that it's catching.

 

[mechanicx]

I don't know what the pressure and heat rating is for that filter but since it is installed on the cold side of the radiator and only seeing -15 psi, I can't see why it wouldn't hold up. Do you know if fuel or dedicated coolant paper elements are different somehow from air filter elements and oil filters? When air filter get wet they seem to clog airflow, and oil filters seem to swell when exposed to water. But maybe liquid flow is not blocked since there are various paper element liquid filters?

 

[onion]

I don't know about different filter papers. I do know that coolant filters industrial applications use a paper filter, and the paper does swell and distort some even in dedicated coolant filters. The one I have in mind is Detroit Diesel's new 15-liter dual overhead cam engine (actually a Mercedes design), which uses a cartridge-type coolant filter (no can). I've changed a few of them, and after a couple years of use they're soft, distorted, and packed full of muddy gunk. I suspect that canister-type coolant filters look the same after some use, but I've never bothered to cut one open and have a look.

Here are a couple pictures of a used cartridge-style coolant filter from a DD15 engine:

As you can see, the filter paper is swelled and distorted, but this is normal. Matter of fact, the ones I've replaced have often looked worse than these.

One of my concerns about using a fuel filter is the glue that holds the filter paper in place. If it's designed to NOT be gasoline-soluble... then it MIGHT be water-soluble. Time and a box-cutter will tell. Like I said, if this filter does hold together internally, then I'll probably try a larger fuel filter with a metal can next... probably another Fram (ugh... I know- but at least their glue will be a somewhat known factor, and they're cheap).

After a couple days use I don't see any signs of the paper swelling or distorting yet (though it has turned the color of DexSludge), and I can see (via tiny bubbles) that coolant is still flowing. This is why I wanted a clear plastic filter- it's just so [censored] much fun. And I'm willing to put up with a slight risk of catastrophic failure in the name of fun... and SCIENCE.

 

[Gary Allan]

You might PM Pete C. with this topic linked. He would know the differences between oil/fuel/water filters. I'd suspect visually they would be identical. The temps for oil and water are the same, but the adhesive aspect did bring something new to question into the mix. I would imagine the fuel filter (typically diesel) and oil would be the same, but water ..

I'd like to believe that they're the same. I've seen him refer to it as plastisol ..a somewhat generic term.

 

[StevieC]

You could always use something like this... It has a metal screen and I used it for a catch can on my Cabriolet for the PCV line but it could be adapted for coolant and it's rated for high-heat.

They also come is huge sizes so you could run it on the big lines that go to/from the engine to the radiator.

Original Thread: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1463111&fpart=1

 

[Gary Allan]

Neat component you got there, Stevie.


I knew I'd come up with something a bit more suitable. A common Y strainer would probably work well. It wouldn't be as fine as an oil or coolant filter, but would be cleanable. It appears that 1/32 is the common mesh used.

 

[StevieC]

Yeah this thing is neat because it would force the coolant through the outside and only what passes through the mesh would go up the center and our the other side. The mesh is pretty fine.

 

[onion]

I should have recorded the mileage on Monday, but didn't think to write it down. But this is a visual update after 5 days of stop-and-go driving, roughly 30 miles per day on average.

This picture was taken about two minutes ago, with the cooling system fully warmed up and pressurized in 90-degree heat. If you look closely, you can see that the plastic filter is 'bulging' a little. I still don't think it's going to be a problem, but you can clearly see the effects of the pressure and heat. A metal inline filter WOULD be a safer option.

When you compare this to a similar photo taken before the car was driven, it's pretty obvious that this filter is accumulating crud. Here's the 'before' picture for comparison: