Temp gauge 99 4.0L

[sholzy]

If it is the cats I want to be sure due to cost.

If your cats are plugged , it would probably run like crap and may even get so hot the cat would glow.

 

[backroad101]

Driveway should be enough. All you need to do is let the air have a high point to escape from, best place is the radiator cap. Just the temp selector, no need to run the blower. Yes, radiator cap, sorry.

Should I be concerned that the coolant resevoir (the one by the windshield washer fluid) is close to full (way past the "fill to here" line)

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[sholzy]

Should I be concerned that the coolant resevoir (the one by the windshield washer fluid) is close to full (way past the "fill to here" line)

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Not really, unless it starts over-flowing often. Then you could have other problems. The way the tank works is, when the coolant gets hot and expands the extra coolant flows into the tank. When the coolant cools it contracts and creates a small vacuum in the system and sucks coolant back into the tank.

If you have other problems, like a head gasket, then you will have combustion pressure getting into the system and push your coolant into that tank. But in this case, it would probably push a lot of coolant and you would see bubbles escaping from the filler neck when the cap is off.

 

[backroad101]

If your cats are plugged , it would probably run like crap and may even get so hot the cat would glow.

If my cats were the issue, wouldnt the temp gauge stay pegged in he red?

 

[backroad101]

Driveway should be enough. All you need to do is let the air have a high point to escape from, best place is the radiator cap. Just the temp selector, no need to run the blower. Yes, radiator cap, sorry.

So I did this until coolant came out of the radiator. Coolant came out for maybe 15-20 sec then stopped. There were bubbles in the coolant if that matters. Added coolant but was not sure how much to add. Can you add to much? If so, what happens? I installed a new radiator cap.

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[mosher41]

If my cats were the issue, wouldnt the temp gauge stay pegged in he red?

My truck must have clogged them slowly....because i never really noticed the decline in performance until it was WAY bad. After I changed them I sure did notice the difference for the good. I didnt find it until the performance was way way off, like no throttle response at all and when it got that bad the temp gauge was UP and Down every 5 or so miles yet I could still feel the exhaust coming out of tail pipe....Converters never glowed as far as I know. But the temp gauge did exactly what yours is doing....I did all of the air removal steps listed above and IT still did it.....check your plugs, see if they appear "ashy" that might give some clue as to how hot the cumbustion chamber is.

 

[backroad101]

I did recently have an issue with plug number 6. Replaced it and the problem went away. With the current issue it only runs a little rough occationally. Most of the time it's just the temp gauge

 

[backroad101]

So I did this until coolant came out of the radiator. Coolant came out for maybe 15-20 sec then stopped. There were bubbles in the coolant if that matters. Added coolant but was not sure how much to add. Can you add to much? If so, what happens? I installed a new radiator cap.

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So after the get the air out of the system thing and replacing the radiator cap with a new one the problem seems better. It seems that with every repair I have done the issue has gotten slightly better. After the rad cap, the issue only re-appeared twice in a little over an hours worth of driving. Not sure since it is cold and snowing that has a part in it. I am taking it into the shop tomorrow as I think I have done all I can. Will see what happens.


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[backroad101]

Found this on a jeep forum in regards to the Cats. Would this work or apply for me in troubleshooting from a temp standpoint? I note that I have not had any noticible loss in power.

Confirmaiton:

1. With the engine COLD, remove the O2 sensor.
2. Drive it to see if the power was resotred.

Pulling the 02 sensor will remove all backpressure built up by the clogged exaust and resore power. If power isn't restored... the problems' somewhere else.

 

[backroad101]

So it is really cold here (below freezing). When I started the truck this morning there was a somewhat loud rattle that slowly went away as the truck warmed up. This actually happened Friday too. Not sure where it was coming from. Truck was fine on the "overheating" side of it until I pulled into the shop's parking lot (approx a 20 min drive). Right before the temp gauge bounced I noticed the heating in the cab went cold. Shop hasn't looked at it yet. Could it be the water pump or maybe the fan? Fan seems to be working fine.

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[backroad101]

Also something I forgot to mention is that I hear a burble-like noise when the heat is on. Is that normal? I think it has always done that. Is that just coolant going through the heater?

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[backroad101]

So I am being told my head gasket is bad. I find this odd as in April 2008 @ 87k miles (I now have 109k) the following was done.

Serpt Belt
Thermostat
Spark Plugs
Resurface heads
Head Gasket

So should I be looking at an additional problem that may have caused them to go bad again. Needless to say I am gettting a second opinion.

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[sholzy]

Also something I forgot to mention is that I hear a burble-like noise when the heat is on. Is that normal? I think it has always done that. Is that just coolant going through the heater?

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That could be air still in the system. When you fill the radiator, make sure the engine is at operating temp and the radiator fill neck is the highest point in the cooling system. The radiator will probably puke some coolant as the t-stat opens and the air works its way to the radiator. At that point add coolant slowly. Watch for coolant movement in the radiator. If you need to increase the RPMs to check coolant movement, you can remove the throttle cable assembly cover and use the throttle cable.

You mentioned earlier bubbles in the radiator. Was it constant bubbles? Do the bubbles increase when you increased the RPMs? If your cooling system is actually air free and full, then bubbles could be a sign of a leaking head gasket. If you have a small leak between a coolant passage and a cylinder it would introduce air into the system which would in turn allow the coolant to boil and cause the engine to overheat.

 

[backroad101]

Had someone look at it today then got a second opinion on my way home from work. Both are saying bad head gasket to the tune of $1800. That sound about right? Any suggestions on getting that price down? Maybe have an engine rebuilder do the work? Also, what would cause it to fail this second time after only 20k miles? Second guy who looked at doesn't think a plugged cat is the cause. He suggested a possibility that the person who did it at 85k miles did not do a good job.

Why are these 4.0L so prone to this problem and what can I do to avoid it again?

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[Earl43P]

That is bad news.

I had a similar issue on a 99 Ex 4.0 SOHC.


Temp spikes and flux.

Found pieces of an old thermostat in the thermostat housing. The brass disk wouldn't pas through the passage, but it would block it and cause temp spikes. I could turn on the heater and get the temp to drop, so I replaced the thermostat and found several pieces adrift in the housing. The installed T-stat was intact, so the PO drove it that way for a while.

Thanks again Mike (MHughes)! I sold that beast last month. Still running, but had some issues and I no longer needed it. Was a good vehicle for the price.


Might get another opinion with a test kit that tells if there are exhaust gases getting into the coolant. Available at AP stores, I don't recall the brand name.