EGR & Intake Manifold Clean Results

Consider the block heater?

 

Do you really think those deposits will ever get hot enough to "burn off" inside a heat exchanger that has coolant flowing through it? If they do, where do you reckon the resulting smoke goes?

 

I don't see @mjoo saying they're "burnt off", just that there's more deposits with short trips. I don't see why that would be either, suspect it happens regardless of trip length, driving style.

 

Hot exhaust gas does not "burn off" the deposits in the EGR cooler. The EGR cooler is a "distiller" of water and soot particles. Collecting exhaust particles is the nature of the beast whether it's hotter or colder as long as there's exhaust moving through it. Research the word "thermophoresis" on google.

In EGR Cooler Fouling - Visualization of Deposition and Removal Mechanisms:

"Higher EGR flow rates and cooling levels required by future emissions regulations exacerbate fouling, or the deposition of soot and HC exhaust constituents, degrading EGR cooler performance"

What are the U of M, Ford, and Oakridge National Laboratory all saying? A larger cooling effect inside the EGR cooler will lead to more soot deposition.

Right, more deposits with short trips (and no block heater). This means the coolant is cold more of the time.

 

My attempt at an explanation:

The EGR cooler is a heat exchanger, basically a tiny radiator. The cooling effect of a heat exchanger is also governed by residence time - the longer the hot exhaust and the coolant interact with each other, the cooler the exhaust will be when it exits the EGR, and more soot will deposit.

The slower-moving exhaust gas from low-speed operation combined with coolant fluid that hasn't warmed up to engine operating temperature will produce the most soot deposits. The hotter, faster-moving exhaust during highway operation combined with warmer coolant fluid will leave fewer deposits.I think this is the source of the "Hot exhaust gas "burns off" deposits myth".

 

So then EGR clogging should track with total number of cold starts (versus mileage or time or driving style)? Urban taxis with one cold start per day (and not much freeway driving) should pull off way miles before cooler clogging than daily freeway (or non-freeway) commuters with two cold starts per day, right?

 

I don’t know if the relationship is linear.

To me this is a complex equation with many independent variables .

But an egr circuit cleanse is one remedy that can be used to ward off the effects.

 

I agree with Ray. Some of the variables would include, but are not limited to:

1) amount of time the car operates while the coolant is below operating temperature
2) amount of time the car operates at city rather than highway speed
3) amount of time the car operates at idle or in stop-and-go traffic
4) temperature of exhaust gases
5) amount of build-up already on the EGR cooler

The idea, though, is that an EGR cleaning is needed regularly for an array of reasons. Given the potential for head gasket failure, the timing of this doesn't seem like something to be too finicky about. If you find after a few cleanings that your EGR isn't all that dirty, you can probably extend the times/mileage between cleanings. OTOH, if your EGR is routinely very clogged, you might want to clean more frequently. This should be re-evaluated if your style/type of driving changes significantly.

Sadly, there doesn't seem to be a way to clean the EGR without removing it from the car.

 

Idle time should be near proportional to number of starts, since the engine normally idles only soon after starts. Is there any EGR flow during idle? If so, it must be very small.
Also sadly, used EGR heat exchangers are not as plentiful on ebay as they were a year or so ago.

 

Maybe someone here will sell you one?

 

For those that have cleaned the EGR cooler with Oxiclean, how many soaks did you do and at some point does the water come out of the exhaust side totally clear?

 

It will depend on how much carbon build up there is. Mine was completely clogged so no amount of Oxi soaks was really doing anything, even after the first trip to the car wash to blast out some of it with a pressure washer. Brown gunk was coming out like a volcano and I couldn't see it getting much cleaner after several rounds of soaking. It took a second trip to the car wash and much better technique with the pressure washer to get it clean.

 

I tried the oxiclean route and did several soaks on the spare cooler I had, but it didn’t get the desired result.

The pressure washer does though and in a short period of time.

And it is handy for other things around the house, like cleaning the grill, prepping a table for paint, etc. Right @Pedal Logic ?

But oxiclean works, just not on the highly clogged coolers.

 

If any of y'all need a spare cooler, I have one for sale cheap. It's dirty though.

 

How much, Aaron?

 

Bob, In the presentation (that I linked above) they also mention your residence time (page 4) "High gas flow velocities reduce trapping efficiency." During my last cleanse, I saw how much the EGR sludge loves to accumulate in the EGR port inside the intake manifold. A build-up in the IM would cause a restriction in the IM and throughout the rest of the EGR circuit. Having a regularly scheduled IM cleanse of every year or so should help keep the EGR cooler freer to some degree because of the resulting high gas flow velocity.

Removing and cleaning just the IM is way easier than doing the same to the EGR cooler. Both the windshield wiper cowl assembly and undercar shield can remain intact and the car can stay on the pavement.

Not sure how helpful that is but, at the amount of miles I'm covering, will prove in 5 years.

 

Woo hoo..way to go guys!

I think the problem with the EGR is that it wasn't 'designed' to be cleaned, etc...hence the difficulty at getting to it.

Unfortunately, it turned out to be a design flaw such that cleaning is needed. I just wish Toyota would fess up to it!

Edit : Oops..I didn't realize I was replying to an old post..

 

What I did ( I think I got the idea from @Mendel Leisk ) was to get a rubber stopper and plug one end up. Then you pour the oxi solution into the other end. It did take quite a few soakings to get it clean.

There is a pic of it in this post :
Hi all, new Prius v owner | Page 3 | PriusChat

 

Any special method like mentioned above as far as using a power sprayer.