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Old 11-4-07, 10:58   #1 (permalink)
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I'm baffled - How come the EGR valve hoses have coolant?

Guys,
I had a malfunction code 16 related to the EGR (1993 Mazda Mx6 V6 LS - Last check I did, I also have a code 17; Oxygen sensor). Although I haven't removed the EGR valve to clean it. While trying to reach the EGR, I found something TOTALLY BAFFLING. There's COOLANT in two of the hoses that exit from the EGR valve (please take a look at the pictures, encircled and pointed in red are the two hoses that come from the EGR). One of them connects underneath the throttle body -EDITED: this is normal

- The other one connects to the thermostat housing. -EDITED: this is normal.

The other two connections to the EGR valve are the copper tube coming from the exhaust (as shown in the rearview of the EGR), and another is the vaccum source coming from a solenoid. Please notice the unique EGR valve that my car has (I haven't seen any one like this in the many pictures I've seen in the net).

So the questions are:
--What does 'coolant in the EGR valve mean?

Picture below. Pointed and circled in RED are the two conflictive hoses that contain coolant -both coming from the EGR valve. What the normal connections of these two hoses?


Top view of the EGR valve. I tested the resistance, and seems to be alright (>5,000 Ohms).


Rearview of the EGR valve - Notice the copper tube


Thanks a lot.

Last edited by robueno; 1-25-08 at 14:55.. Reason: bigger pics

1993 Mazda MX6 LS V6 2.5 L MTX >111,000 miles
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Old 11-4-07, 12:31   #2 (permalink)
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EGR gases are recycled into the intake charge to reduce combustion temperatures and help the car burn cleaner. [allegedly].

how else do you expect those hot exhaust gases to cool down?

damon™

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Old 11-4-07, 15:03   #3 (permalink)
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That's the egr that was used on '93's. In '94 they changed the position sensor on top of it (made it smaller and had a connector rather than wires/connector). And dmark is right, the coolant is there to cool the valve and that gases that go through it.

If you're getting code 16 then you have to remove it and clean the inside of it. Good luck with that, the 23mm nut is one serious pain in the a$$ to remove. Unless someone's removed it once before and was kind enough to use antiseize when they put it back.

http://www.redlinegoods.com/cgi-bin/...1&aid=195&p=34

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Old 11-4-07, 19:50   #4 (permalink)
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Thanks dmark101 & Renboy

I appreciate your kind responses dmark101 and Renboy. I finally got over the fact that coolant flowing through those 2 hoses cools down exhaust gases. I never heard of it, not even after searching and researching the damn EGR valve, after visiting hundreds of web pages, downloading tons material, reading forum questions and responses. I even went to the library and photocopied charts from MITCHEL manuals!!. Thinking I was being thorough, I guess that now I'm baffled on how fragmentary information is provided. Now I understand how naive I was.

Definitely I tried to remove the EGR valve, but from the top it's virtually impossible, especially since I couldn't even get a good angle to position and move the wrench for the 23 mm nut. Before that, a friendly mechanic lifted the car, and looking from underneath we couldn't see a good space to work. He simply shied away from working on this car. But I'm persistent, so let me bother you once again.

How exactly did you open working space to loosen that 23 mm nut?

Detailed instructions would be extremely helpful.

--
On second thought I was considering alternative, especialized tools for this job. I found the following 22 mm Angled Socket HEX, but I couldn't find a 23 mm. Are you guys sure it's a 23 mm instead of a 22 mm? Sorry for the pain. I'll see if I could find any tool like this in AutoZone, O'Reilly or NAPA. Please make any suggestions for tools (extensions) or approaches. Thanks.



Thanks. Good night.

Last edited by robueno; 12-22-07 at 16:25.. Reason: Update

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Old 11-6-07, 13:33   #5 (permalink)
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Positive it's a 23mm, no doubt.

You have a few options:
remove the crossmember and exhaust collector and work from underneath

remove the intake manifold and work from the drivers side

remove nothing, use the force, and work from the passenger side

Try hitting the nut with a penetrating oil every day for a few days before you do this, it may help. And if you feel brave, try to remove the nut when the engine's hot. Or if you can maneuvre a torch in there to heat it up. As far as tools are concerned, a 23mm crowfoot will probably be your best bet.

http://www.redlinegoods.com/cgi-bin/...1&aid=195&p=34

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Old 11-6-07, 14:12   #6 (permalink)
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Try a flex head socket wrench, I haven't taken off the egr, so I don't know if it will work, but looking at the socket wrench might give you an idea. Amazon.com: Proto 5257A 3/8" Drive Round Flex Head Ratchet: Home Improvement

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Old 11-7-07, 2:00   #7 (permalink)
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Quote:
Originally Posted by Renboy View Post
That's the egr that was used on '93's. In '94 they changed the position sensor on top of it (made it smaller and had a connector rather than wires/connector). And dmark is right, the coolant is there to cool the valve and that gases that go through it.
hmm. i've removed the valves from both 93's and 94's and each time they've been identical.

i do know that with the 95 model year, the sensor was changed, as well as the connector used to hook up to the sensor. i found this out when i bought a brand new EGR valve from ford a few years ago. ford was nice enough to include a harness adapter, so that people with the 93/94 model could use to connect their connector to the new sensor.


as for removing the EGR tube from the valve, i've always found it easier to use a crescent wrench. when i first removed the tube [to install my headers], it was a PITA, so when i reinstalled the tube, i used some anti-seize lube and didn't torque it down so tight that it was too hard to remove again.

and i agree on the nut size, it's definitely a 23mm, which is an odd size but we've got a couple of other bolts on the car that use that size socket or wrench.

damon™

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Old 11-7-07, 2:06   #8 (permalink)
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Baffled. hehe

Ive worked on to many motors, 93 through 96. Ive seen 3 different styles.

There all crap just like every other EGR in this world.

Dont use a cresent wrench to remove any of the tubes. They strip parts easy.

Use a flare nut wrench


If it starts to strip. Use a Pipe wrench.

If it doesnt budge, Use heat (torch)


To remove the EGR from the manifold..
The easiest way would be remove the whole exhaust manifold and the EGR as a whole. (unbolt manifold, unbolt egr from head) Dont try removing the EGR itself because its usually impossible in the tight space.

Last edited by KING6; 11-7-07 at 2:11..

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Old 11-7-07, 23:18   #9 (permalink)
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dmark, you could be right, it may have been 95 that they were changed (now I'm not sure).

King, there's no way of using a 23mm flare nut in that space. Unless you take it out with the manifold like you said.

Another option is to get rid of the front and rear engine mounts and twist the engine to get more room.

http://www.redlinegoods.com/cgi-bin/...1&aid=195&p=34

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Old 11-9-07, 16:13   #10 (permalink)
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Thanks everybody. Karma to all of you for so much knowledge poured into my humble and naive question. I'm looking for the tools (so many options) to tackle the job. I'll let you know. Thanks also for your suggestions on the many different approaches. Regards.

1993 Mazda MX6 LS V6 2.5 L MTX >111,000 miles
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Old 11-18-07, 1:46   #11 (permalink)
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Vacuum or lack thereof seems to be the problem

Background: Code 16, CEL on, I couldn’t clean the EGR valve because of difficult access to it. Idle is steady at ~700 rpms; now and then I hear backfires but nevertheless very poor gas mileage. So…

-Upon closer inspection, both ports of the 2-ported EGR valve solenoid were broken (maybe originally were, or any of the two technicians who shied away from fixing my car broke the ports). Any way, I replaced the solenoid with Mazda 626 one from the junkyard. But to no avail, Code 16 and CEL-on were still flashing on my dash. Interestingly, my sunroof stopped working.

-After acquainting myself with the anatomy of the EGR system and having the air intake in place + all hoses connected, I repeated EGR valve test: I just disconnected the hose that communicates the EGR valve with the 3-ported EGR vacuum solenoid and attached it to a manual vacuum pump (to the EGR valve side). I started the car, let it reach normal temperature, and I created a vacuum of about 5.0 inches Hg with the purpose to open the EGR valve and cause recirculation of exhaust gases. Immediately, the idle became rough, indicating that the EGR valve might be O.K. because now exhaust gases were being ‘recirculated’ into the engine. So I assumed the EGR valve is OK and rather began troubleshooting a possible vacuum misconnection/leak upstream of this point.

-I checked all the vacuum connections, hoses and compared against the vacuum charts available in this great forum. Everything seems correct, with the following exception. Please refer to the picture attached, which most of it isn’t mine but I just use it here for illustrative purposes.

-In my car, vacuum port (labeled by me as #14 on the passanger side of the VRIS#2) doesn’t not hold vacuum when applied externally, nor it has vacuum when idling. If it were clogged, it should hold vacuum, right? So it must be leaky. So I plugged it, but still code 16 remained on. So I decided to bring an alternative source of vacuum using an unused port here labeled as # 2 beside the VRIS#1 actuator (normally should be plugged -with a mini-condom as somebody else said in another thread). This port has vacuum in the normal range (i.e., sucks real good). I’ve driven about 25 miles so far, and the CEL came on just for a few seconds, but most of the time has been OFF. Interestingly, my sunroof is working back again. Thus, it seems that I just achieved a temporary solution by bringing a strong source of vacuum, that probably works only at mid- or closed-throttle, failing at WOT (wide open throttle). In addition, I seem to hear a hissing sound from the intake manifold which I think locates to the spark boots/intake runners toward the firewall (locations ocho / nueve spraying throttle body cleaner in different spots clockwise from the throttle body. Please take a look at my video). Also I tried blowing air using a dust remover to see if was any displacement of some soap/foam I applied, but was inconclusive. It may take some time for the movie to be available, so in the meantime use as key words 'vacuum leak'..

YouTube - Diagnosing a vacuum leak in intake manifold

My interpretation is that I might have a broken vacuum chamber or vacuum reservoir, thus explaining why vacuum port #14 neither provides vacuum nor it holds it. Bringing another vacuum source like from port #1 is only temporary.

Another thing. I noticed that there’s an empty corner toward the passanger side of the engine, as if someone had removed something. Ford probes have a vacuum chamber-like box, possibly related to the HVAC, but I’m not sure. Could the previous owner removed what was there? If something should go there in the Mazda’s, then how would that affect the vacuum? Many thanks, regards, Robueno.





Last edited by robueno; 2-4-08 at 23:13.. Reason: Images didn't work before

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Old 11-18-07, 8:38   #12 (permalink)
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This is what I wrote to accompany the youtube video.

"After getting a Malfunction indicator light (MIL) or Check engine light (CEL) flash in the dashboard, a trouble code related to the EGR (Exhaust Gas Recirculation) was present. "Exhaustive" diagnosis was done mainly by checking vacuum hoses, solenoids, EGR valve position sensor and the EGR valve itself --by applying external vacuum with the car in idle (which should become rough with an intact EGR valve). Pretty much everything checked out, with the exception of a vacuum "nipple" source which upon application of external vacuum didn't hold vacuum nor 'sucked' with the car in idle (good vacuum should be produced with a closed throttle plate). Since the source of vacuum used for the EGR valve is 'stored' in vacuum chambers/vacuum reservoirs, a leak in their connections could explain the EGR malfunction code. Thus, here I performed a 'propane test' but using Throttle Body cleaner instead --Carb cleaner is supposed to be equivalent. Be careful, this is FLAMMABLE. Have somebody look at the RPMs in the tachometer while you spray carb cleaner in suspected areas (use a straw). In this case I started with UNO (1) at the firewall, driver's side of the air intake and proceeded clockwise in 10 total spots - the last 6 correspond to pits where spark boots enter the engine. The flammable carb cleaner taken at the vacuum leak proceeds into the intake plenum enriching the gas:air mixture and increasing the engine speed, which is the readout here. I'm NOT responsible for any mishaps you might make. Actually I do NOT recommend this test, if at the end you do not want to spend the whole weekend disassembling or assembling the intake manifold (it's up to you)."

You guys don't need the disclaimers, but this is the description I posted in YouTube.

Last edited by robueno; 2-4-08 at 23:14.. Reason: Video description

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Old 11-19-07, 11:33   #13 (permalink)
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Code free so far

I found the problem; a broken nipple in a vacuum reservoir, whose symptoms are consistent with the lack of vacuum in the main source (labeled as 14 in my previous picture), and also consistent with a positive propane test (instead I used throttle body cleaner). Replacement vacuum chambers were procured from a local junkyard. No codes yet. Let's see how long they last.

Any way, I'd like to hear your thoughts on the HVAC thingy that my car lacks (or maybe all Mx6's). For sure, I've seen it in a Ford Probe.



Last edited by robueno; 2-4-08 at 23:15.. Reason: removing typos

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Old 11-22-07, 20:38   #14 (permalink)
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There's nothing that's supposed to be there. Except maybe an aftermarket alarm.

http://www.redlinegoods.com/cgi-bin/...1&aid=195&p=34

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