P0303 and Coolant

Try cleaning the plug, you may have a bit of carbon in the nose cone causing an short. It that doesn't 'cure' it replace that plug.

Cooling system: I recall your system holds 12 quarts but check your manual.. DC recommends you upgrade to the new spec G-05 coolant although you may continue with the old spec. (see below)

Flushing: If there is a layer of slime in the expansion tank or the cooling system has been neglected It might be advisable to chemically flush or clean the cooling system. The flush-n-fill kits make this easy and thorough.

I did several flush/drain cycles to be sure the nasty old coolant was gone and then let the hose run several minutes after I was sure it was completely clear.

A flushing of the heater core with distilled water would be a good idea, you can clamp the hose to force the distilled water back-down-and out.

Add your 6 quarts of Zerex Original Green or Zerex G-05 concentrate to the system and another quart (7th) to the expansion tank and then top off with additional distilled water.

That should give you -57/+270 protection.

You can use the Tee to 'burp' the system that otherwise would work out over the next several days of driving. In a few days check the expansion tank and re-top as necessary.

The coolant drain in the block is the way to go, if you can get at it. Sometimes you can't, or it just isn't reasonable. In that case some kind of flushing is indicated. How much flushing you do, depends on what kind of junk comes out. Pouring in distilled water before the last drain is a good idea, because you really don't want to leave much tap water in there. I had good luck pouring a quart or two of distilled water through the heater core, with the hoses disconnected from the engine. In most vehicles you can bypass the annoying "burp" phase, by making sure that the engine is full, up to the cylinder head. You can use a heater hose fitting or a temperature sender as a bleeder if you want to do this. If you plan to use the tee, make sure it is in the hose that goes to the head, not the one that connects to the water pump, and that it is uphill from the engine.

It's a lot simpler than it sounds, unless you do something wrong.

Earle

So I'll need two gallons of coolant? Is one radiator flush better than another? I have always used 'Water Wetter' with good results. Will 'Water Wetter' work with the Zerex G-05?

Thanks,

Carl

DC states a warning in the manual in bold letters that you shouldn't use wetting solutions..

I used Zerex flush, if your cooling system is really dirty the Zerex cleaner is stronger.

Two gallons of coolant should leave you a bit to spare.

How exactly do you know that you "have always used 'Water Wetter' with good results"? Because the car still ran afterwards? I don't think you need it. Water and ethylene glycol are pretty darn wet already! Billy Ray says so too, and he's some kind of chemist.

If the coolant presently in the system is pretty clean, and you can get the drain plug out of the block, then I don't think you need to flush with anything but water, if at all. Don't forget to rinse the overflow bottle and the heater core. These are spots often missed.

Earle

You can drain and refill the coolant all you want -- probably a good thing by the way -- but this will not fix the error code.

If I got the code you got, I'd be looking at stuff like spark plug wires or the coil (if the motor has a dedicated coil for each plug). I certainly would not spend time and money on completely unrelated systems, especially when those systems have their own series of codes to tell me when they are not feeling well.

Heh, I read this as two separate issues. ;^)

You are right that he needs to address the spark issue too.

Earle

Relative to the P-code, ALL he needs to address is the spark issue.

It's probable since you just replaced the plugs, that you got one that is defective. I have seen this in the past. Change #3 again, check wiring and coil connections (if present), clear the CEL and retest.

If you must flush, use very low pressure compressed air to clear tap water out of the system. I've also pulled heater core hoses and cleared them separately.

Also, this is a good time to drop hints that you need a good code scanner, since Santa is generous this year.

So just from the P-code you've already determined it's a spark issue. Wow. You're good.

Yes. What would you deduce from a P0303 code?

HINT The code means the #3 plug is not firing properly, which by definition is a spark issue.

Thanks for the responses, guys. I cleared the code last night and drove about 20 miles, it hasn't since returned. I'll change the plug today anyway. There are no plug wires on a 2k. Instead, there is a coil rail with three coil packs. The P0303 and the coolant are completely unrelated issues, I just posted in one post to keep the clutter down.

My research has shown that the P0303 problem is known to be a heat soak issue with injector #3. Apparently, sometimes the heat from the exhaust manifold will creep up to injector #3 on a hot shutdown, causing a misfire. The fix is an insulating wrap around injector #3.

The coolant in the radiator right now is brown. I assume someone drained the radiator and re-filled it with standard coolant. That's why I want to flush the system. I read that there is a 7-hour flush. Apparently I just add it to the radiator (after draining a small amount, of course), and it cleans the system during a seven-hour drive. I'll be driving back over to Seattle next weekend (a five hour drive) and I plan to change the coolant while I'm there. Am I barking up the right tree here?

I have seen positive results with using water wetter in an all ready good cooling system. I would not expect to see results using a it in a clogged, contaminated, or otherwise maulfuntioning system. Per reccomendation here, I will not add it to the XJ. Just curious why they say not to use it?

Brown coolant is undoubtedly bad, but it doesn't necessarily translate to scale and sludge in the coolant chambers of the block or blocked radiator tubes. I would flush the system with water, and only resort to a chemical flush if big pieces came out. Otherwise, you can assume that most of it is already in suspension. Another tell-tale is the bottom of the overflow reservoir. Nasty pieces will tend to accumulate there because it doesn't really have circulation. I am against flushing with chemicals unless you have reason to believe that they are necessary, and then you have to take extra care to rinse them all out afterwards.

When you say "positive results with using water wetter in an all ready good cooling system" what do you mean exactly? Lower reading on the temperature gauge? I don't get how you can tell, that this stuff is doing what they say it does.

Earle

This is from the Factory Service Manual, it is printed in bold typefont: "CAUTION: Do not use coolant additives that are

claimed to improve engine cooling."

Under Chemical Cleaning:

CHEMICAL CLEANING

If visual inspection indicates the formation of

sludge or scaly deposits, use a radiator cleaner

(Mopar Radiator Kleen or equivalent) before flushing.

This will soften scale and other deposits and aid the

flushing operation.

CAUTION: Be sure instructions on the container are

followed.

I used Zerex 'Flush' (the milder or the two) because the girl that had the WJ before me allowed her corner Quickie-Lube to 'top off' her expansion tank with Prestone Universal which turned the factory G-05 into reddish-brown slime.

I also removed the expansion tank and inoperative coolant sensor and cleaned them in the basement laundry tub. The sensor worked fine after a thorough cleaning and reinstallation.

You can check on the Jeep web site for recall notices, there was a recall several years ago to install some reflective insulation on the 4 liter engine manifolds.

You may be able to clean spark plug number 3 but then replacement is only a couple dollars. The Jeep engines seem to not like the new high tech sparkplugs so it would probably be best to avoid the +2, +4, & iridium plugs.

Thanks, Billy. I only ever run the copper Champ's in my 4.0's. $1.29 each. I have recently (less thank 2000 miles ago) replaced all 6 plugs. I bought one new and will replace plug #3 today.

Thanks,

Carl

Positive results meaning a much lower reading on the gauge. For now, I'll skip the chemical flush and the water wetter.

Thanks for the responses. I will replace plug #3 today and find out more about injector #3 insulation.

Carl

P0303 means the PCM has detected a misfire in the #3 cylinder. Do you see the word SPARK in that definition?

HINT There's a lot of things that can cause a misfire, and some things that can cause the PCM to THINK it detects a misfire.

I changed the spark plug today. The one I pulled out looked still brand new. No fouling, white ceramic, clean center electrode, gapped at .035. I replaced it anyway. I reset the computer and all seems OK for now. I'm sure it will come back eventually.

Carl

Not always. A fuel or compression problem in one cylinder will also set this code. If you unplug one injector, you'll get it. I've also seen