2004 overheating (possible bad head gasket questions)

[c_anthony27]

I picked up another TJ today
2004 sahara
185,000 miles on it
4.0 automatic

previous owner said his mechanic told him it needs a headgasket because it tends to overheat

It was late when I drove it home
but I checked the coolant fluid level and that was good before i drove it home

10 mile drive
it ran fine at slightly under the 210 deg mark on the gauge while on the parkway

pull off the parkway
and the temp gauge shoots up to the red and the warning light comes on
(i ran it for less than 30 seconds after that happened)
also the jeep started having a slight hesitation when the temp shot up

so what should i start checking tomorrow AM before I just go tear the head off.

This will be the 4th Jeep I currently own and my 10th overall
all with 4.0 engines and some with way more miles than this and I have never had a blown headgasket before

I feel like it could be something else
just curious what you guys think
or suggest

 

[Chris]

Check the compression and do a leak down test first off.

It could be that the radiator is low, has air bubbles in it, or the thermostat is sticking.

 

[Fishtaco]

Maybe its the head gasket just like the Mechanic told the PO but more likely something worse, PO,s usually down play a fixer upper problem when selling else they would just fix it!
You have had 10 jeeps and you are asking why an overheating jeep is hesitating to drive? hate to be critical but any and every overheating engine hesitates to operate correctly and some even stop when they get too hot, have you ever had an engine overheat?
If its a head gasket you may have blow back and bubbles or effervess in your radiator viewed with cap off running or even oil particles in the radiator flowing past as the coolant circulates, if its a cracked head you can get the same blow back or opposite coolant sucked in the oil making it milky.
I am sure if it was a compression issue and the PO filled it with thick engine seal you would have much less power now when its cooled down after overheating and you would also more than likely be blowing amounts of Blue grey smoke out of the exhaust, pure white smoke(steam) = head gasket or cracked head black smoke= running way too rich blue grey smoke = oil burning usually rings, compression shot = less than normal power overheating or long / no start.
I do hope though for your sake that its just a thermostat or air in the system but I am sure a mechanic would have eliminated that first not last?
Could you smell the overheat when you picked it up? Overheating engines have a distinct overheating smell that lingers even in the cabin.

 

[c_anthony27]

Maybe its the head gasket just like the Mechanic told the PO but more likely something worse, PO,s usually down play a fixer upper problem when selling else they would just fix it!
You have had 10 jeeps and you are asking why an overheating jeep is hesitating to drive? hate to be critical but any and every overheating engine hesitates to operate correctly and some even stop when they get too hot, have you ever had an engine overheat?
If its a head gasket you may have blow back and bubbles or effervess in your radiator viewed with cap off running or even oil particles in the radiator flowing past as the coolant circulates, if its a cracked head you can get the same blow back or opposite coolant sucked in the oil making it milky.
I am sure if it was a compression issue and the PO filled it with thick engine seal you would have much less power now when its cooled down after overheating and you would also more than likely be blowing amounts of Blue grey smoke out of the exhaust, pure white smoke(steam) = head gasket or cracked head black smoke= running way too rich blue grey smoke = oil burning usually rings, compression shot = less than normal power overheating or long / no start.
I do hope though for your sake that its just a thermostat or air in the system but I am sure a mechanic would have eliminated that first not last?
Could you smell the overheat when you picked it up? Overheating engines have a distinct overheating smell that lingers even in the cabin.

the previous owner is a friend of mine
I actually had to convince him to sell me the jeep
it needs some other repairs also
and he is not mechanically inclined at all
I bought it with the intention of swapping a new engine in since I have a nice running takeout motor from a 2005
I just swapped a new engine in to my YJ project 2 weekends ago

Anyway for some reason I get the sense that his mechanic is not the greatest around and Im not sold on the head gasket diagnosis

The other thing I forgot to mention last night was the check engine light started flashing prior to the temp gauge shooting up
from what I understand those are usually a sign of a clogged cat
which can in turn cause the engine to run hot also ?

Im going to put the scanner on it today and see what codes come up
and check the fluid levels
give it a compression test and go from there

 

[williambmac]

A flashing SES light is usually do to a misfire. See what cylinder was misfiring with your scanner and pull that spark plug.

If I was a betting man, I would say that the misfire was being caused by coolant getting into the cylinder.

 

[c_anthony27]

A flashing SES light is usually do to a misfire. See what cylinder was misfiring with your scanner and pull that spark plug.

If I was a betting man, I would say that the misfire was being caused by coolant getting into the cylinder.

so i didnt get much time to mess with it before work today

had to do a new radiator and trans cooler in the yj

but the TJ spit out these codes when i put the scanner

p0302

p0135

p0304

p0455

 

[williambmac]

does your code reader/scanner show real time data?
if so look at the misfire counter. how many misfires on cylinder 2 vs cylinder 4
P0455 large evap leak
p0135 bank 1 sensor 1 O2 heater circuit malfunction.

Did you check the radiator today? low on coolant? anything in the oil?

I would also want to confirm that it is actually an overheat issue and not electrical,

 

[c_anthony27]

does your code reader/scanner show real time data?
if so look at the misfire counter. how many misfires on cylinder 2 vs cylinder 4
P0455 large evap leak
p0135 bank 1 sensor 1 O2 heater circuit malfunction.

Did you check the radiator today? low on coolant? anything in the oil?

I would also want to confirm that it is actually an overheat issue and not electrical,

my scanner is a cheaper crafstman one
as far as i know it just reads codes and clears them

I did not get a chance to check fluids or really look at it today

hopefully tomorrow i can get it in to the garage and start checking it out and give it a compression and leak down test

but yeah i really want to rule everything out before i go and take the head off,
i dont mind doing the work at all
i just want to get a proper diagnosis of whats going on with it

 

[c_anthony27]

Spent some time going over it today

Coolant level is okay
fluid doesnt look any different than old coolant fluid does

checked the oil and its very black like in need of an oil change
but definitely not “milky” like a blown headgasket would show

did a compression test and this is what i got for each cylinder
#1 - 160lbs
#2 - 125lbs
#3 - 160lbs
#4 - 160lbs
#5 - 175lbs
#6 - 175lbs

plugs all look like they havent been changed in a decade
but not overly white
and not fouled with oil

any ideas what i should check next ?

 

[williambmac]

Here is what I would do,

Re-check your compression on cyl 2. although it's within spec 120-150psi. I would re-check dry, then add a couple squirts of oil and re-test it.
You do have a difference of 35psi between cyl 2 and the rest. So it does look like you have something going on in that cylinder.

It could be worn rings, carbon build up on the valves.

Additional diagnostics such as a leak down of that cylinder would help.

You said the oil is filthy, Run the vehicle to temp, get the oil good and hot, then drain it.

What are the old ass plugs gapped at. Excessively worn plugs could contribute to your misfire.

These are just a couple things I would do before really getting into the misfire issue.

Then you need to figure out the overheat issue.

Just remember with 180k on the motor anything is possible.

 

[Rubicon88]

Water pump

 

[JKP]

Also check the fan clutch if it doesn't overheat on the hwy, but does at low speed/idle.

 

[AMS417]

Simplify this. First thing to do is a combustion gas test on the cooling system. Go rent a tester and buy the fluid to do the test. It will tell you if combustion gases are entering the cooling system. It it test bad, pull the head and fix what's wrong. If it test good, start working out what parts of the cooling system are not functioning correctly.

Best of luck.

 

[c_anthony27]

Simplify this. First thing to do is a combustion gas test on the cooling system. Go rent a tester and buy the fluid to do the test. It will tell you if combustion gases are entering the cooling system. It it test bad, pull the head and fix what's wrong. If it test good, start working out what parts of the cooling system are not functioning correctly.

Best of luck.

yeah i think thats where i am going to start
part of me is leaning towards just swapping a new motor in

but ill test the coolant for exhaust gases and go from there