So I’ve been driving since New Orleans (23hrs) and my temp shoots to 260 and check gauges light pops on. I was parked with it running at a gas station luckily. I replaced the thermostat about 9mo the ago and also flushed cooling system multiple times and installed the peak adapter for a water hose to make it easy. Coolant was spraying out of my radiator cap which I also replaced about a year ago. I was thinking maybe water pump is crusted and stuck. Had it towed to local dealership and they’re saying blown head gasket. And that they would have to do the head gasket before fixing the overheating issue. I honestly feel like a new cap could solve all of this. Haven’t dropped the oil so I don’t know if it’s been mixed with coolant but I added about a 1/3 quart and it looked clean thru the cover. Please any help would be much appreciated. Thanks

 

How did the dealership determine it is a head gasket? Did they test for exhaust gas in the cooling system?

Also, what year is your XJ Cherokee? What engine?

 

I doubt it. Sudden overheat like that? That's not what a bad radiator cap does. And you were overheated and parked it, but left it running? If the head gasket wasn't the original problem, that probably toasted it. When your temp spikes like that the only correct thing to do is shut it down NOW.

Ask the dealer WHY they are saying blown head gasket. Make them prove it. I"m betting that's it, but you do want to be sure before dropping that coin.

BTW, looking at the oil is a very unreliable way to determine if you have oil in it. You should not pay any attention to that. It has to have quite a lot of coolant in it, and for a good while, before you'll see anything that way.

 

A simple way to check for a blown head gasket is to let it cool down completely, then put a pressure tester on the rad cap, don't pump it up, then start the engine. If pressure starts climbing immediately, it's a blown gasket.

I'm thinking the reason for your overheat is the electric fan didn't come on when you parked it. The engine was already heat soaked during your driving and needed instant cooling when you stopped, which it didn't get.

 

With a 2001, you might be in a bit deeper than just a blown gasket. Google 0331 head defect... there's a better than even chance your head cracked if it was/is original.

You can get a new clearwater head (https://www.cylinder-heads.com/produ...head-complete/) for about $600 if it is cracked. The google results should show you what to look for, you can sometimes even see the crack apparently.

 

2001 sport. I’m up here now trying to figure it out but I brought a cap and coolant so we’re find out soon enough.

 

So they weren’t able to prove it had a blown gasket. He said the tech said he could smell exhaust fumes. That wasn’t enough proof for me. Replaced cap, flushed cooling system. Runs around 200 for about 20 mins then temp shoots to 260 but the valve cover is still only warm. Overflow tube is clogged pretty bad so I’m guessing that’s why coolant starts coming out the cap. Could that be why it’s saying it’s overheating?

 

if I don’t have a pressure tester can I just start the engine up from a cold start and see if it builds pressure by using the pressure release valve on the cap instead?

 

WTF kind of "Dealer" can't run some basic diagnostics to determine whether there are traces of exhaust in the coolant?!? You can go to Autozone and get test supplies to do a block test.. while you're there grab the coolant pressure tester to run Dave's test and get some new hose for the overflow.

Also make sure you have an IR temp gun - if you don't already own one, Harbor Freight sells a cheap-o that's sufficient for occasional use. I'd also suggest a multi-meter so you can do a test on your coolant temperature sensor (CTS - the sensor in the t-stat housing)... the gauge gets the temp reading from there on an 01. The IR gun will tell you the measured temp at the housing (again, where the CTS is reading from) and the Multi-meter will allow you to do a basic test on the CTS to make sure it's not gone bad on you.

Basically, the major point is - you have odd behavior - your suspects are "head/head-gasket", "Temp misreading at CTS". It's not going to be a clogged overflow or bad cap, it's either the temp is reading wrong, or it's right and there's a problem with the cooling system. You can sit around and hope it's something simple, or you can start diagnosing the problem systematically and figure out what is going on. If I were you, I'd start with confirming the temperature as read on the gauge and go from there.

Bear in mind that the 0331 head cracking is most definitely REAL and COMMON. I would not at all be surprised if you have it - however, you won't know until you TEST!

Autozone or another parts retailer will rent you the block tester tool (you'll have to buy the consumables) AND a cooling system pressure tester --- for FREE (you need to leave a deposit that covers the tool cost). Take advantage of that loaner tool program.

 

No. Go get a pressure tester loaner tool from your local parts retailer.

 

Head gets warm, crack opens up, blows exhaust into coolant, temp shoots up. Please do the test Pat & Dave suggest, and stop lying to yourself.

 

tests were completed properly and no blown head gasket. Find on water pump we’re chewed off pretty bad and even though I had replaced thermostat about a year ago, this one was defective. 1600 is what the dealership quoted me just for head gasket. I’m back on the road for 400$. Crazy how that works huh?

 

"Another tank of gas and back on the road again!"

 

Oh one of these? I should have thought of that. Been there, done that.

 

That is why everyone around here will tell you --- test, test, test --- narrow down, eliminate potential failures and you eventually will find the point of failure. Fixing the root cause point of failure is always a heck of a lot cheaper than just throwing parts and theories at things until you hit.

Glad to hear you're back on the road and your engine is good. If you have an 00-01 with the original head, you need to be extra careful about not overheating it, so keep an eye on that temp gauge brother!