Overheat and smog fail

The XJ is my kids school/beach runner. We blew a (poor fitting) coolant cap at a gas stop about 450 miles into a hot road trip in August.

I replaced the cap, filled her up and kept an eye on her. We proceeded to wheel it up in Tahoe for the week and it made the 500 mile trip home no issues. He drove it around town, no issues. Figured the bad cap was the cause. Noticed some stress cracks in the coolant bottle.

A week or two after the trip I took it in for a smog check. It failed with high CO and NO. Plus it overheated during the test.


Today I set out to replace the coolant bottle and found separation at the top radiator hose nipple on the radiator.

So now the questions:
- I assume a new radiator is in order, is it a mistake to go with $99 plastic tank, lifetime warranty radiator? Seems most cost effective unless they just flat out suck.

- is it likely that the coolant cap and/or leak at radiator was initial cause of overheating or more likely that was resultant damage due to overheating caused by other issue?

- why didn't it overheat on the way home from Tahoe (freeway wind flow?) it made it over the CA I5 Tahone pass after 400 hot I5 miles.

- what is the likely hood that the overheating is causing to the smog fail?

- figured I'd change out upper and lower radiator hoses, is it worth changing out heater hoses.

- any other no brainers to take care of or upgrade while the radiator is out?

BTW: water pump and t stat are a couple years old. All coolant boiled out or drained so far has looked green/yellowish and generally clean.

After battling with my closed cooling sytem for over the last year I can tell you that once the cap or the bottle cracks you will start overheating. If you are going to replace the radiator the plastic tank ones work fine, I just installed one from Oreilly's, Just make sure you burp it good or it will wanna run hot on you.

If you dont feel like dealing with the stupid reservoir on there every few months just convert to an open system using a radiator for a 92xj, it will drop straight in. As far as the emissions go I can't help you, what did the smog guy tell you? They usually have a little insight as to what is going on there.

What year jeep? Automatic? Can you post the actual smog test data?

1988 Auto

Smog readings:
CO: .94/1.26 (max is .75/.95)
NO: 1094/1107 (max is 714/616)

I have read that high temps can cause increased NO readings, not sure about CO?

Hoping that fixing cooling issue with new radiator, chasing down vac leaks and a basic tune up (plugs, wires, etc) will correct it.

Maybe after that a new Cat?

I read that you can sometimes tell if it is the Cat by looking at the plugs, if the back ones are burned more than the front ones???

Sometimes a Cat will fall apart inside the housing, and at times move around to where it blocks and backs up the exhaust some. That can cause a power loss and maybe some backed up heat.

Check the spark plugs, if they are black, it is running rich, which burns out the Cat converters (and over heats them while doing it!!!).

If the plugs are black, the O2 sensor-wiring-relay set up all needs to be inspected, tested and fixed (what ever is bad, relay, wires, or O2 sensor).

The engine runs cooler in open loop (dead O2 sensor set up), but will overheat and burn out the Cat converter (then it may run cool if the Cat converter is not broken). If the engine was running too lean, it would overheat all the time.

The high CO is either poor fuel burning (needs a tune up), and or a bad Cat, and or a bad O2 sensor set up. The high NOx may be a bad Cat and or a bad EGR valve.

Fix the cooling system, do a tune up, plugs wires, cap and rotor, then run the O2 sensor tests in my thread here on "oxygen sensor tests" (use the search tool). IF the O2 sensor set up is bad, replace the bad parts, if not then use an IR gauge to test the front and rear of the Cat for temps once warmed up. The rear should be hotter than the front. Also check for throttle response under load, low gear WOT to see if it sounds like the Cat is plugged up.

Then I would go in for a retest, to see if the Cat needs to be replaced as well. If you get the CO way down, but not the NOx, then the EGR may be stuck or leaking.

High CO is usually cat related, however it can also be EGR related, and it can also be related to high NOx.

Last time I had to smog my jeep (1990 XJ laredo) it was coming back high NOx. (it still had a relatively fresh replacement cat on it)

The things I would recommend doing:

Check and Clean EGR system

Check for vacuum leaks (this can affect EGR valve function)

Check/Replace O2 Sensor

Check CAT

Double check radiator/bottle - a hot running engine will fail NOx

Before you go in for smog check, run the car mostly out of gas, put about 5gals of 91 octane in, and run that around in it for a while.

Theory of operation: older engines can get carbon buildup, which can pre-ignite the gasoline, this is usually minor, but will boost NOx, running a higher octane of fuel fights the knock as it is more difficult to ignite than regular 87 octane fuel.

Wish I had better news for ya.. But this will probably take a cat replacement to pass. However, I would fix the cooling system, clean the EGR and check vacuum first as most of those should be fixed beforehand, and are mostly cheap/easy fixes or need to be done anyways.

OK so old radiator is out. Besides the crack at the upper hose nipple, some corroded fins it looked pretty clean. There was some deposit/debris at laying on the bottom.

Everything I got out of the radiator was green and clear until I actually turned if over and dumped it into the bucket, then I got some brownish, not much.

The lower hose was melted and soft at the bottom turn near the tranny cooler lines. Super soft, but not melted through.

I stuffed a hose into the upper hose connection at the engine, pulled the temp sensor at the back top and ran water through the engine. I put my hand over the lower hose connection and let the block fill up a few times and drain and let the hose run for a while.

Everything that came out was greenish/clear until it was clean clear water. NO rusty or brown stuff at all.

NOW
off to Napa to pick up a cheapie radiator, upper and lower hose.

Next:
- Anything else to consider while the radiator is out?
- Hopefully this resovles the coolant issue and I can start chasing down vac lines.
- After that it is tune up, re-read the above recommenations and maybe check into the CAT.

Any comments or suggestions greatly appreaciated (I am not a mechanic)

Will the valve cover breather tubes play into these problems.

I have a visual run through:

the large breather tube connection at the valve cover is basically NOT connected, it was just sitting in place and is disintegrated to hell. Anybody know the part number for that?

The flex hose part of that same tube that connects at the air box was full of oil and disintegrated NOT connected.

There is oil residue on the intake tube and on the throttle body butterfly. It seems that the breather tube at the valve cover was just sitting over the 1" hole in the top of the valve cover and maybe the intake was sucking oil in???

The small vac line at the back of the valve cover just slips out of the rubber connector and is covered in oil/grease.

HOPING that the radiator, change these breather vac connections and tube up will get me there.

Ecomike said:

Sometimes a Cat will fall apart inside the housing, and at times move around to where it blocks and backs up the exhaust some. That can cause a power loss and maybe some backed up heat.

Check the spark plugs, if they are black, it is running rich, which burns out the Cat converters (and over heats them while doing it!!!).

If the plugs are black, the O2 sensor-wiring-relay set up all needs to be inspected, tested and fixed (what ever is bad, relay, wires, or O2 sensor).

The engine runs cooler in open loop (dead O2 sensor set up), but will overheat and burn out the Cat converter (then it may run cool if the Cat converter is not broken). If the engine was running too lean, it would overheat all the time.

The high CO is either poor fuel burning (needs a tune up), and or a bad Cat, and or a bad O2 sensor set up. The high NOx may be a bad Cat and or a bad EGR valve.

Fix the cooling system, do a tune up, plugs wires, cap and rotor, then run the O2 sensor tests in my thread here on "oxygen sensor tests" (use the search tool). IF the O2 sensor set up is bad, replace the bad parts, if not then use an IR gauge to test the front and rear of the Cat for temps once warmed up. The rear should be hotter than the front. Also check for throttle response under load, low gear WOT to see if it sounds like the Cat is plugged up.

Then I would go in for a retest, to see if the Cat needs to be replaced as well. If you get the CO way down, but not the NOx, then the EGR may be stuck or leaking.

Click to expand...

mine was boarderline when i smogged it, and it kept losing power, progressively over time. it finally got to the point where i couldnt hold 65 on the highway. cat was broken and clogged.

NAPA has the hose-vac tube assy. It is called the CCV, CrankCase Ventilation system. Old threads here have the part number, just Google it. If the system is not clean, leak free, and properly attached and flowing it can blow oil backwards into the air filter, and box area. IT IS part of your smog problem. but may not be all of it.

Thanks Mike. Super helpful!

I ordered both sides of the vac assembly plus the grommet for the small vac connector at the valve cover. Plan to install all, clear out small tube from valve cover to TB. Case down any other vac leaks, tune up and retest. After that I'll be looking at the CAT.

88trailcrawler said:

Thanks Mike. Super helpful!

I ordered both sides of the vac assembly plus the grommet for the small vac connector at the valve cover. Plan to install all, clear out small tube from valve cover to TB. Case down any other vac leaks, tune up and retest. After that I'll be looking at the CAT.

Click to expand...

Be sure to replace the small vacuum line on the rear of the VC. It is critical to air flow rates on the CCV, and clogs up real easy!!!!

i was under the impression that a clogged /bad cat is often the cause for both high Nox and high CO. your high NOX and CO lead to believe your cat is bad.

before you pull the cat, I would first run sea foam through the intake. then i would replace cap/rotor/plugs/plug wires and then a new o2 sensor. calibrate the TPS . a new rad and hoses wont hurt. water pumps are cheap as well, so that is something to consider doing at the same time. call cooling system close to done. dont forget to burp it.

OK I am screwed.

Installed the new radiator today, filled it up. Had ass end up hill on the driveway, pulled the temp sensor, filled it up until coolant came out the temp sensor. Turned it on and off a few times, pulled temp sensor and got coolant.

Had the boy run it around the block. Temp shot up to 210. Pulled it in the driveway and it blew the coolant cap.

I did have the air box out and CCV ports open on the valve cover (didn't thinkt hat would affect temps) I am have vac harnes on order.

New issue is that all the valve cover bolts were like hand tite and I saw oil bubbling out of the front of the valve cover.

I NEED to get past this coolant overheat issue before I can chase down any other issues.

Mechanical fan was spinning, electric fan never kicked in.

I need to know what's next. I can't justify paying shop rates for a mechanic to chase these things down.

BTW water pump and t-stat are only a few years old.

My problem is that I can fix the resultant issue, but I don't know what is causing the quick overheating.

OK you say this is an 88, Renix, I assume with the plastic bottle and cap at the passenger side firewall?

Is it all still stock renix hoses and cooling system components?

The only way I know of to get air out of the renix system is remove the radiator hose at the T-stat, elevate it. Then remove the heater hose that is attached to the steel tube pressure outlet of the water pump, disconnect it between the steel tube and the heater core-bottle T, or heater valve, so that it is open to air at both ends!!!

You can also remove the rear head temp sensor. Leave the jeep flat!!!!!

Then fill the coolant bottle and the upper radiator hose slowly, refilling until the bottle stays 3/4 full, and the upper hose stays full.

Once all three openings (Temp sensor in the head, the heater core-water pump hose and the upper radiator hose) are full to over flowing, then quickly reconnect both hoses and reinstall the Temp sensor in the head near the firewall (drivers side).

Then run the engine with the coolant cap OFF the bottle, and run it at 2000 rpm in park. It will foam in the bottle, but if there is any remaining air it will purge to the bottle (it bypasses the T-stat), and you will need to add coolant to the bottle if the level drops to half full. Be sure the heater valve is open if there is a heater valve!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


Now, you may have a bottle-cap problem, as all the aftermarket bottles and caps for Renix are JUNK!!!!! Get a Volvo plastic bottle cap (Stant brand is only $5-$8) and use it right away!!!!!!! A temporary fix is to put a 2" worm gear hose clamp on (around) the Renix bottle cap!!!!! That keeps it from popping off.

Hot wire the E-fan for now!!!! I run my all the time, unless it is under 45 F. I installed a winter/summer toggle switch on mine. The Renix E-fan switch is on the exit end of the radiator, a bad design location when the radiator starts to scale up a little, and your E-fan switch may be bad!!!!! It should turn on at 185 F coolant temp on the radiator exit (equal to about 205 F at the T-stat housing with a new radiator).

After 6 years of standing on my head here with others, I discovered that the Renix system likes trap air in the top half of the radiator that NEVER gets out, due to a poor plumbing design. Unless you follow my steps, you are only getting the radiator half full of coolant!!! It is the major problem!!! The second problem is air can not get out of the block with out that heater core to water pump hose open to the atmosphere while filling.

88trailcrawler said:

I did have the air box out and CCV ports open on the valve cover (didn't thinkt hat would affect temps) I am have vac harnes on order.

New issue is that all the valve cover bolts were like hand tite and I saw oil bubbling out of the front of the valve cover.

Click to expand...

The CCV has nothing to with the overheating. But is important to fix for other reasons.

New CCV will help with the oil leaks at the valve cover, once the bolts are tight, if the gasket is any good. The CCV creates a vacuum under the Valve cover, removes blow by gasses in the crankcase that cause pressure in the crankcase.

Thanks again Mike. Maybe there is hope. I'll give a shot.

Note from DJ
If you have the valve cover off for any reason you might consider doing this modification while you have it off.
Cruiser’s Valve Cover Mod
Post # 46 by cruiser54 on 5-07-2012
http://www.naxja.org/forum/showthread.php?t=1072534&page=4

Also Aluminum Valve Cover Bolt
Torque = 55 inches-pound
Bolts = 1/4 - 20 x 1” W/ 3/8” Hex Head

Note; Clean bolts and clean out bolt holes. On intake manifold side, these holes are not open bottom holes. Check all holes with a stiff straight wire which will loosen up any debris.

If debris is in the bottom of the hole the bolts will bottom out on debris and torque to specifications but gasket will not be properly compressed.

Update an more questions.

Overheating:
- Appears to be resolved.
- made system was full and burped. (Thanks Eco Mike)
- e fan temp sensor was bad, I put a jumper in for now will put an in cab switch later
- put a ZJ fan clutch in and a net T-stat with new housing


Valve cover gasket and CCV:
- Done with the CCV tube mods
- installed new CCV vacuum harnesses

High idle:
- may be resolve
- sensor grounds at block near dip stick were loose ( I had trouble with these when I did the ground cable upgrade and my crappy connection failed).
- I put a temp jumper ground in and the high idle seemed to drop

Tune up:
- done
- plugs, wires, cap, rotor
- plug tips were a bit gritty
- inside distributor cap was green.

Cat converter:
- after tune up the XJ had an odd idle sound.
- I thought on plug wire might be loose
- one was a bit mid aligned (fixed it)
- checked under the XJ and the Cat was glowing bright red


So that's the report.

My plan is:
- rig up a legit ground for the sensors. (Think I am going to extend the wires and ground them up high because that stud by the dipstick is a bitch)
- got to a muffler shop and get the cat replaced.

And finally my question:
- given the initial smog test results, my repairs and findings, is there anything else I should do/check before a retest?
- do I have a reasonable chance at passing now?

- are local muffler shops a bad idea if I am considering all new manifold to tail pipe, my manifold and connection toward cat are pretty crusty.