Red Hot Exhaust Manifold

Hi PPL

I have a 86 Hyundai Excell, the ehaust monifold gets yellow hot and is
visable during daylight hours. The problem only happens when the car is
driven
down the highway for 10 min or so. The first thing I suspected was a clogged
catalytic converter since it is bolted to the exhaust monifold. Ripped out
the catalytic converter, now the monifold is only red hot. The car was
running rough
so I suspected a timing problem. I reset the crankshaft and camshaft
timing, set the
distributor timing to 4 degrees BTDC (as per specs), the car idles better
now but the
monifold is still red hot. Tried a different pair of plugs, no go. Made
sure the choke was opening,
it's fine, ERG opens fine. Checked all vacume lines and replaced the ones
that were broken. Since I recently replaced the head gasket, I retorqued the
head, no go. Made sure the valve lash was correct (suspected that the
exhaust valves weren't closing all the way), no go. Replaced the timing
belt, no go. If I take off timing belt, when the crankshaft and camshaft are
dead on the timing marks, and turn the crankshaft back (counter clockwise)
two teeth on the timing belt, the exhaust manifold doesn't get red hot at
all and the car has lots more power. The only problem is that the idel is a
little high, and the timing range is off. What I mean by timing range is:
the whole range adjusting the distributor timing is 30 degrees BTDC to TDC,
none for ATDC. I's really stange that I would have to move the crankshaft
back two teeth to fix the problem, all logic says that the crankshaft and
camshaft should be set to thier respective timing marks. Does anybody any
any advice as I'm still dealing with this problem.

Thanks in advance
Mike AKA Deefer Dog

A word of advice "never pet a burning dog!!"

 

Wow! An on-topic post. ;-)

Seriously though, how many miles are on the engine?

 

160,000 Km
Looked at the on line Hyundai manuals, nothing to help me there.
Do you have any suggestions?

 

coolant?

 

Humm. 1986 Excel. 160,000 Km.

I'm inclined to say that if it runs better with the timing belt offset by 2
teeth to leave it there.

If it was me, I'd leave the timing gears at their normal position and just
retard the distributor timing until the problem was resolved. That engine
has a lot of wear on it and things are a lot looser inside than they were
new.

 

The engine is too lean. Why, I have no idea. Check timimg, O2 sensors,
etc. BTW, a clasic clogged cat symptom is stalling when you give it
gas from a stop, so I don't think that would be your problem. Bottom
line, not enough fuel.

 

Yep the the timing seems to be the issue here. No O2 sensors! No Cat, if you
read the orginal post, I revoed the thing as I suspected that it was
clogged. BTW when I removed the cat, the manifold wasn't as hot (darker
shade of red)
so the engine is getting the proper vacume and fuel, if it was running lean,
it would run rough and I wouldn't be able to drive down the highway at
140Kph, defianatly not the cat and a lean fuel mixture. Ohh BTW the plugs
are a light tan colour suggesting that the fuel mixture is OK. Thanks for
the suggestion.

Mike

 

You know what, I did notice that the coolant was a little low on the
overflow the last time I changed the timing. Filled er up right away. The
coolant is at -43F, I suspect this is what you were suggesting? Coolant
doesn't run through the exhaust manifold, just the intake manifold, and the
car isn't over heating, at least by the guage in the car.
Thanks!!! Mike

 

I'll try that, retarding the timing on the distributor at little more.
Instead of 10 BTDC (4 BTDC on specs) I'll try 15 BTDC
Thanks

 

http://www.hmaservice.com/webtech/iindex.asp?id=8631#_8631

 

One possibility is a clogged or defective EGR valve. If you open the valve
by
hand when it's cool it should remain open when you cover the vacuum nipple
with a spare finger. If you open the valve by hand with the engine running
(before it gets hot), the idle should drop and/or stumble/stall.

Does this engine have some sort of air injection into the exhaust manifold
as
well as into the cat? If so, the diverter valve may be shot and it's pumping
air into the manifold all the time. If your exhaust is too rich (misfire),
this would
cause the glowing.

I suspect that your cat was an empty canister when you removed it?

Bob

 

The ERG valve is opening. The canister did have a cat in it and it was
clogged, when I removed it, the temp of the exhaust manifold went down
(darker red colour) one thing I did notice is that the coolant temp went
down, as though the car is running a little cooler. I suspect that this is
because the exhaust is taking the heat instead of the head. Now why is this
happening, that's the question!!! It's not a warn crankshaft sprocket as
suggested in the previous post, as I have already taken the spocket off...it
was tough to get off and there is no play, so I guess it's not worn. Any
other suggestion?
Thanks in advance.
Mike : )
"Never pet a burning dog!"

 

The EGR valve may be opening (i.e., the rubber diaphragm is intact),
but the EGR passage thru the intake manifold back to the head may
be all clogged up with carbon, especially after 17 years. Open the
valve by hand or with a vacuum pump while the engine is idling, and
see if it stalls (it should).

The purpose of exhaust gas recirculation is to lower the temps in the
combustion chamber a couple of hundred degrees to reduce the
formation of NOx. As a side effect, it should also drop the temp
of the exhaust manifold.

If it's clogged, unbolt the valve and clean it out with a screwdriver.
Clean the passages as best you can with a long thin screwdriver
or something like an old speedometer cable attached to a
variable-speed drill.

BTW, have you ever tried decarbonizing the head by spraying water
into the carb while the engine is at fast idle? Use something like a
spray cleaner bottle, don't pour water by hand into the carb or you'll
break a piston or rod due to hydraulic lockup. This should lower the
compression back to normal if it's on the high side due to carbon
build-up. You'll get lots of black carbon out the tailpipe, but eventually
it will subside when it's all cleaned up, leaving you with a little white
steam.

Bob

 

I know that the ERG valve is opening. The diaphram that opens it comes off
of the exhaust manifold with a vacume line. Remove the vacume line and the
exhaust resinats differently inside cat canister, which is attached to the
exhaust manifold.
The different sound that the exhaust makes tells me that the ERG is opening,
however, is it clogged with carbon as you suggested, I'll look into that.
Hope you are right as this problem is starting to become more than a problem
LOL
Thanks for the excellent suggestions Bob

: )

 

Hi Bob
I made a mistake when I was saying that the ERG was on the exhaust manifold,
it's on the intake manifold. I was talking about the wrong part as I thought
the secondary air control valve was the ERG. Anyhoo I did as you susggested,
except I didin't decarbonize the head.


I took off the ERG and inspected it. The valve was gummed up with oil
sludge, cleaned it up (break cleaner) and made a new gasket for it. When
depressing the diaphragm, the valve wasn't sticking and was able to swish
break cleaner back and forth between the two openings for recycled exhaust.

I reamed out the two ERG passages (on intake manifold) with a used
speedometer cable and a power drill. I was able to feed about 2 and a half
feet into each passage. One of the passages that goes towards the carb, was
clogged with oily sludge, but I was able to clean it and spray some break
cleaner into it to further soften up the sludge. Put the whole thing back
together, ran the car down the road for 20 min and I have the same problem,
red hot exhaust manifold. With the engine at operating temp I revved the
engine, the ERG diaphragm opens all the way (the back of the ERG is open to
see the diaphragm) pushed on the diaphragm with my finger, the idle changes
slightly. So it appears as though the ERG is operating as it should. Any
other suggestions?



Mike

 

I'm stumped. On other cars (not Hyundai), I've seen red-hot
catalytic converters when there's a lot of unburned gas due to
bad spark plugs or wires. In this case, you'd notice a rough
idle most of the time. It's also possible that the engine is running
too rich (or as others have suggested, too lean) at highway
speeds due to a leaky or clogged carb. You might be able to tell
which way it's running by examining the spark plugs. If it's too rich
one or more will be black and sooty. If too lean, they'll be really,
really clean & white. Normally, they have slight tan deposits on
the ceramic part. Check the plug wires on a dark night. When you
put your hands near the wires, there should be no arcing or
glowing spots. If there is, you need new wires.

Does the air injection on this car come from an air pump? On some
engines, the air injection is just sucked in thru a filter without a
pump. Follow the hoses from that secondary air control valve to
see where it comes from. If it's a pump, try removing the belt or
plugging the hose. If you remove the air source, the unburned gas
may just go out the back pipe instead of afterburning in the manifold.

If you think it's the carb, you can try getting a carb rebuild kit and have
a go at taking it apart, cleaning it and putting things back together.
You may discover a partially clogged jet or air bleed.

By the way, I find that carb cleaner works a lot better than brake
cleaner on oily deposits. (Carb cleaner dissolves paint, brake cleaner
generally doesn't, and carb cleaner is a lot cheaper.)

Do you know what the idle is on this engine right now? It should be
around 700-800, and opening the EGR by hand should result in more
than a slight decrease in idle speed. Is the idle cranked up to 1100-1300
to compensate for really bad performance at normal idle? If you want
to see the difference, try running the engine with the EGR valve removed.
It shouldn't run very well at all. If it does, spray carb cleaner into the
passages that you reamed out, a little at a time, until it breaks thru
the remaining blockage.

I hope one of these suggestions works. I'm also assuming that when you
took the head off, you put the head gasket back on with the correct side
up. I'm also assuming that all the vacuum and vapor hoses are back where
they should be. I remember reading a post here a few years ago where
someone switched a vapor return hose with a vacuum hose, and the engine
wouldn't run because of all of the extra gas being sucked in.

Bob

 

Yeppers I'm stumped to
Ya I had a Cavalier with a bad cat, the carpet caught on fire LOL
The plugs are a tan colour, so the mixture seems to be correct. The spark
plug wires are new and not arcing. There is no air injection system (air jet
valve beside intake valve) on the 86 model. The car is idling fine so I'll
assume for now the carb is ok.
what else...ummm let's see...oh ya, the idle is around 900 RPM when the car
is at operating temp. I'll remove the ERG and see if the car runs like shit
to verify that the ERG passage has been cleared. If not then I'll do as you
suggested and try cleaning the passage again. The head gasket wasn't put on
back wards as there is only one way to align the bolt holes. If I put the
head gasket was on backwards, how would that affect the ERG passage? I was
under the assumption that the ERG passage went from the intake manifold
through the head and not the block. As I mentioned I was able to feed 2 feet
of the speedometer cable through both passages. Do you think that is far
enough? When ever I took a vacuum line off, I made sure that it I put it
back in the correct place, but I'll double check that tomorrow. I was also
thinking that, I could take off the intake manifold, that would give me a
better view of the ERG passages and do some extra cleaning if nessary.

Thanks for the suggestions, if this doesn't fix the problem, then I think
I'm going to drive the car off of a cliff. : (
Bye for now
Mike

 

The thing with most head gaskets is that on many engines, you
*can* put them on upside down (flipped left to right) and the bolt
holes still line up, but the coolant passages don't, so you have
partially blocked passages and an overheated head.

The idle is a bit high (s.b. 750±100) . Does it refuse to idle at
lower speeds?

I couldn't find the online manual for your Excel at
www.hmaservice.com/webtech , the closest I could get is 1988.
Do you have a feedback carb and an O2 sensor? If you do and
your O2 sensor is dead, the ECU might think that it needs to
increase the O2 by leaning out the mixture as much as it can,
but not so much that you'd notice a performance problem at
highway speeds.

Looking at the 1988 manual, your secondary air control valve is
supposed to let air into the exhaust manfold when the engine is
warming up, then it switches to sending air downstream to the
2nd cat under the car. If this valve is burnt out or always open,
air would always be going into the manifold and causing the
red-hot condition. Try plugging the hose from the valve to the
manifold and see if things improve. There should also be some
sort of check valve where the hose meets the manifold to
prevent hot exhaust from going back thru the hose and burning
up the valve.

The cliff is starting to sound much better.

Bob

 

Yep that is true with the head gasket, however for the after market head
gasket that I bought, it will fit on only one way.. The coolant circulates
IE: I have heat inside of the car and there I get oil to the head.It might
be possiable that I might have some how put the head gasket on backwards as
anything is possiable, 99% I didn't. The idle is a tad high, it's because I
have a weak return spring for the Primary Throttle, I've shorthened the
spring (more springy : )) however the idle sometimes is a little high.
Anyhoo I think I'm going to take the carb and intake manifold off today, and
try reaming out the ERG passages in the head and intake manifold. If I don't
find some kind of restriction then I'll take off the head and see where I'm
at from there. Ohh ya one thing to mention, the head isn't as hot as it's
been before, but that might be because it's fall here is Saskatchewan,
burrrrr getting chilly outside.

 

Hey Bob, me thinks I got it figured out.
I think the whole problem is timing advance. Remember I was saying that I
have to set the crankshaft back two teeth to eliminate the glowing red
exhaust manifold problem. Currently I've left the crankshaft at a half of a
tooth backwards (as close to timing mark as I can) and the distributor
timing has been left at 10% BTDC (book says 4%)
If I change the distributor timing to 4% BTDC, the problem gets worse and
the car has hardly any power on the highway. Checked the spark plugs and now
they are black. Changed the distributor to 12% BTDC, plugs are starting to
go to a dark tan colour. I'm thinking that the timing isn't advancing enough
(when driving down the highway) because, either shifting the crankshaft back
two teeth or, with the crankshaft back half a tooth, advancing the
distributor timing to 12% BTDC, has the same effect. I checked the
distributor timing, with a timing light (12%BTDC) and revved the engine, the
timing doesn't seem to move much from the timing mark IE: the timing blur on
the crankshaft pulley doesn't go advance to say 20% BTDC
Now here is where things don't make sense, how can I wipp down the road at
140Kph if the timing isn't advancing? Maybe it's because I've set the timing
to 12% BTDC????
Any suggestions???