Blown head gasket or cracked head?

[Metalmoto]

Please help.
2001 Jeep TJ 4.0 with 216,028 miles on it. Was running fine until yesterday. It's only used for short trips, rarely see's 45 MPH. Started up fine yesterday, first thing I notice, temp gage is not working. I always let it idle to operating temp.
Also notice idle is high, 1,000 after warmed up. OK, was going to vist my wife in the hospital 4 miles away.
But first, I stopped at the Pharmacy, 1/2 mile from home. Turn off car, in the Pharmacy about 15 minutes.
Back in Jeep. Cranks fine, won't start. Try again, giving it a little gas this time, struggles a little but starts and runs.
Still high idle, still temp gage dosent move. I shut in down, notice temp gage moves down a couple mm when key is turned off. Restart is the same, needs a little gas to start.

At this point, I know something is wrong. Don't want to get stranded at hospital. So, I drive back home.
Open the hood, check oil. Level is fine, although it looks a little too clean. Quick check of underhood fuses.
Check coolent level in overflow tank, an inch over full. Remove radiator cap, full of coolant. Been using Zerex G05 since I bought it 5 years ago. Leave radiator cap off. Start up Jeep, within 15 seconds, coolant is coming out of radiator.
Shut it down. I have a combustion leak tester that I used before on my wife's chevy Impala.
Was going to try it on the coolant overflow tank. Because of obvious reasons.
Although I pretty much determined blown head gasket or cracked head. Jeep was never overheated.
I will try the combustion leak test.

But how come the Temp gauge quit working? Still looking for the sender...

Thanks in advance,

Dave

 

[ColoJeep]

If the coolant level is too low , it won't transfer heat to the sensor . My bet is a cracked 0331 head since it's a 2001.

 

[JKP]

Remove the oil cap, look straight down and check for coolant, that's where they crack.

Temp sender is on the thermostat housing.

 

[Fakahatchee]

216,000 miles, you did good. My 2001 cracked the head at 58,000 miles.Replaced the head with a Clearwater head and been running great ever since.

 

[Moglocker]

216,000 miles, you did good. My 2001 cracked the head at 58,000 miles.Replaced the head with a Clearwater head and been running great ever since.

And it’s not a bad job either.

 

[Metalmoto]

Coolant level is fine. Jeep started fine today. Idle was a little lower.
Revving the engine sprayed coolant in my face. Failing water pump?
Can't see any dripping coolant. Need to do combustion leak test to be sure.
Got off track checking my wife's Liberty battery. It's been sitting for months.
Might be my backup vechicle...
Battery seems fine, but won't start car. Thinking the starter is dying.
Will start with a battery charger jump.
Keep everyone posted on the Wrangler. Too cold outside now.

 

[Chris]

If the coolant level is too low , it won't transfer heat to the sensor . My bet is a cracked 0331 head since it's a 2001.

X2 to this

 

[Metalmoto]

And it’s not a bad job either.

I have the tools. Money for parts is the issue. Unemployed at the moment.
Factory where I worked, burnt to the ground. I was working when something exploded.
Everyone got out safe.

 

[Metalmoto]

Remove the oil cap, look straight down and check for coolant, that's where they crack.

Temp sender is on the thermostat housing.

Temp sensor question.
Internet keeps saying sensor on thermostat housing is for ECM.
Another "sender" on the rear of the block is for the dash gauge.
I dont see it. Attached is a pic of where it's supposed to be.

 

[Moglocker]

Temp sensor question.
Internet keeps saying sensor on thermostat housing is for ECM.
Another "sender" on the rear of the block is for the dash gauge.
I dont see it. Attached is a pic of where it's supposed to be.

View attachment 678122

Yep maybe read it on a scanner but need to get that gauge working

 

[Metalmoto]

Yep maybe read it on a scanner but need to get that gauge working

I didn't even think of that. I got a good scanner. But yeah, I need that gauge working.
I don't want to drive it and make it worse!

 

[Moglocker]

I didn't even think of that. I got a good scanner. But yeah, I need that gauge working.
I don't want to drive it and make it worse!

Might not be a head problem

 

[Metalmoto]

Might not be a head problem

I am thinking that too.
I'll hook up my scanner, it's not great, but it tells you more than just codes.

 

[JKP]

Temp sensor question.
Internet keeps saying sensor on thermostat housing is for ECM.
Another "sender" on the rear of the block is for the dash gauge.
I dont see it. Attached is a pic of where it's supposed to be.

View attachment 678122

There's only the one on the thermostat housing that feeds the PCM, which drives the gauge. It's not a "real" gauge. YJs had the setup you described.

Download the FSM for your yr from Resources section.

 

[Metalmoto]

Hey, I am getting somewhere. First I tried the trick to check the gauges and idiot lights.
All worked fine. Then I hooked up my scan tool for live data. And selected ECT.
Here's the weird part. For the first 5-10 minutes, it was saying the coolant temp was 6 degrees-14 degrees, bouncing around between those numbers. Then suddenly the temp went up, also on the dash too. As soon at it started warming up, the idle went down. I kept running it until it hit 190-200. And the dash gauge was working too.
That was probably why it was hard starting. The ECM thought it was really cold, and adjusted accordingly. I guess I should replace the temp sensor, as soon as I can.
Otherwise, I want to "THANK EVERYONE" for your thoughts and advice.

I really don't know if the engine has ever been rebuilt, but was told the trans was rebuilt, and it had a new oil pan and starter. Oh, when the starter died last year, finding a good rebuilt starter was a joke! After buying 2 rebuilt ones, one lasted 4 starts, the other would just grind on the flexplate. This seems crazy, but the best one I bought was off Amazon, made in China. And it was cheaper than a rebuilt one. The mating flange was much thicker and it's been working fine for a year now.
Last year, it kept stalling and refusing to restart until it cooled off. Oh yeah, I replaced the CPS first, and it was fine for 6 months. I finally got a fuel pressure tester, and the fuel pump was the problem. That was a big job for me, took me a while, but let's just say, I don't give up easily. I've been repairing my own cars since I was 20. I am 61 now. I had some mechanics work on my cars. But the crap they did was horrible. Stuff like a drywall screw holding down the distributer cap... appeared the mechanic had teenagers, doing the work.
Other mechanics just want the easy jobs. Tell me I need a whole new exhaust, when I replaced it myself 2 years before. No way is was shot already. THANKS AGAIN...
I hope I can get a couple more years out of her.

 

[JKP]

If you look down the oil fill hole and see TUPY cast in the head, it's been replaced with the updated version. If not, you probably have the original one.

 

[Moglocker]

If you look down the oil fill hole and see TUPY cast in the head, it's been replaced with the updated version. If not, you probably have the original one.

If he has the non tupy,do not let it overheat ever.

 

[Metalmoto]

If he has the non tupy,do not let it overheat ever.

It's not a tupy, so I will be careful. Thanks!