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Manifold red hot???

DanMan2k06

DanMan2k06

NAXJA Forum User
Location
Damascus, MD
So I've been flushing my cooling system lately trying to make sure everything is clean. Today I hooked up the Prestone flush kit with the T-in to the heater hose. I stuck a couple pennies under the throttle to keep it around a constant 2k rpm's. Everything was going fine, until I noticed the exhaust manifold was RED hot. I mean glowing. All the runners, right after the block. I had it running for about 5-7 minutes before I shut it off.

What could cause this? The exhaust isn't clogged, not that I've thoroughly investigated it but it sounds fine and has plenty of pressure blasting out the tailpipe. It could be running lean I suppose, but again the engine runs perfectly fine. Any ideas?
 
BASICS--Year/engine/etc.
 
DANG you got me Joe. For a second I forgot I made a new thread instead of posting the other one where I told specifics of the new purchase.

-1999 Classic
-AW4
-130k
-Whole new cooling system. New rad, water pump, fan clutch, tstat, housing, rad cap, hoses, and cleaned resevoir and heater core.

Bought with a "blown head gasket". I dunno if this was the previous owner's neighbor's cousin's brother's opinion, or if he actually took it to a mechanic to check it out. When I replaced the water pump, the fins were sitting inside the block. Coolant was the worst I've EVER seen.

The only other thing I could think of besides what was mentioned, is that the cooling passages in the head are totally gummed up. But I flushed everything out until it was totally clear. Of course you never know for sure...
 
Yeah, not coolant related, more likely what 87Manche pointed you to.

I would, however, get some Prestone or Bar's Leak or Zerex radiator CLEANER--put it in and run for 3-6 hours, then neutralize and put in a good 30/70 coolant mix--30 ethylene glycol and 70 distilled water. Run that during Summers and 50/50 for the cold times.
 
That's what I was thinking. And no, they THANKFULLY don't have the pre-cats. I believe those came around in 2000+.

I'll take a look at the o2 sensors tomorrow and see how they're acting.
 
well things that I would look for.

an O2 sensor that's all kinds of screwed up.
Timing that's hosed
leaking fuel injectors
TPS issue (not likely)
Map issue (possible)
I'd try and get a wideband O2 on it and see what the mixture is like. a local dyno place could help you with that. Other than that, I'd consider replacing the upstream O2 sensor just as a matter of routine maintenance. They do go bad with time, and 130K miles is time. The one after the cat is basically there to check the cat function, the one in the downpipe is the one that trims the fuel.
 
I know a couple guys that have some connections with a local turbo shop, I'm sure they could help me with the wideband. I was thinking the same thing about replacing the upstream sensor just as part of the usual maintenance. I really have no idea how this guy treated the car so everything will get replaced eventually lol.

I forgot to add, we have a 98 xj as well. When I get some time I'll swap over everything on the throttle body and see if it makes a difference. But I have a feeling it's a little deeper problem.
 
UGH. Well it's been sitting a few days, I thought I would start it up again and see if it was just a one time thing.

It's night time now, and after literally about 90 seconds the manifold was red again. Right where the runners meet the head. Time to start looking for some serious problems.
 
Pull the plugs and have a look.
If it were running lean, the plugs would have a white coating.
I can't say what our engine would run like but I suspect you would
get some pinging (pre-detonation) when you're driving and nail the gas.
I had an old Chrysler 5th Ave that had the glowing header symptom.
In that case it was a clogged catalytic converter.
 
I pulled the plugs when I did the compression test a few days ago. They were white, but looked normal nothing excessive. I'm thinking about cutting out the cat and seeing if it's clogged. Although the exhaust coming out the back is steady and pretty forceful. Hard to believe it's clogged.
 
Like the man said, do a spark plug check. It was how you did it before O2 sensors. :repair:

Do a vacuum check. It could spot a leak or a plugged CAT.

Clogged injectors can cause lean running but normally not every cylinder will be the same. Either way, if it has set for a while, run a can of BG44k through the gas.
 
-retarded ignition timing (you would notice less power and a very hard struggle to reach high rpms when under load)

-retarded physical timing (jumped a tooth on the timing chain) usually the engine sounds like its got a cold air intake on it, and again it will struggle to get to high rpm and be low on power

-clogged exhaust of some sort, typically the cat

-poor fuel pressure maybe? since running very lean will do it.
 
Remember when you first start it up the engine is in cold loop till the tstat hits 180. Up to that point the ECU emissions don't do anything and the O2 sensors are ignored/not read. I wonder if the PO put High test in it and it's not completely burning in the cylinders.
 
Likely a normal condition as a result of running it unladen at that rpm for so long.

I saw that on my buddy's 99 when we hiked up the idle like that to jump/charge the battery on my XJ when the alternator went on the way home from Moab.
It never showed any adverse effects or any symptoms of anything wrong before or after that.
 
Got access to a shop with a DRB or electronics tools? throw the DRB, oscilloscope, or ANALOG multimeter on the O2 sensor and see if it's varying at all.

It's probably about time since it's got 130k on it, but it is a good test to do first.
 
Could be normal, but 90 seconds seem awful quick for it to start glowing. I have seen manifolds glow when a cam break in was done. Make sure that the distributor and cam sensor are indexed correctly. Even if you didn't touch it timing chain stretch could cause it to be off.
 
RichP said:
Remember when you first start it up the engine is in cold loop till the tstat hits 180. Up to that point the ECU emissions don't do anything and the O2 sensors are ignored/not read ./....
Click to expand...


Welllll .... Not really ..... ;)

As long as the heated O2 sensors have warmed up to operating temp within the few minutes it takes ...... The computer should have gone closed loop at about the time the temp gauge reached 65'f.


OP .... you getting any codes ... especially O2 sensor codes ???

Normal guess for your problem would be blocked exhaust ... cat particularly .... but .... :dunno:
 
No codes, that's what stumping me. One of the guys at work used to be a chrysler tech, and he made a good point. Maybe it's just not meant to do that?

Meaning you start up the engine and immediately jam it at 2k for a few minutes. I'm gonna take it for a test drive and pull over periodically to see if it happens under load/wind/stop and go idling conditions.

I sure as hell don't think it's normal... As I said earlier, the plugs were fine. No abnormal whiteness or worn down electrodes.
 
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