- Location
- West Bountiful, UT
Short version... Is there any such thing as an intermittent head gasket leak?
Trying to diagnose an issue with my '06 LJ, Jeep 4.0. Could use some thoughts...
Twice, over about a month this summer, the radiator let loose with a sudden blast of coolant out of the cap. Once about a minute after turning it off and the other time while driving. And the engine immediately overheated both times. But was not overheating, before the cap vent. My guess, the sudden depressurization caused the sudden overheat. But, I actually don't have a clue.
Both times, stopped, took the cap off, let it cool down. Started it up and the problem was gone.
So I replaced the cap. The old one was a 20 lb parts store cap. I've had cruddy luck with parts store parts the last couple of years. So I ordered a Mopar cap, which is the correct 18 lb. Drove close to 2,000 miles without a hiccup and thought life was good.
This weekend, after almost three days of driving, over 600 miles total, about half offroad. The cap started to steam and "spritz" coolant. Not a violent eruption like with the previous 20 lb cap. Mostly just steam, and just enough coolant to make my windshield a mess (my hood has a vent just above the fan). But, the engine wasn't over heating. Temp was running like maybe 4 degrees warmer than usual, but holding steady there.
Stopped, took the cap off, let it cool down. Started it up and the problem was gone.
Next day, it started up again, worse on the steam and coolant spritz out of the cap. But the engine still wasn't overheating. But, while stopped and letting it cool, it was gurgling bubbles out of the radiator into the overflow bottle.
Stopped, let it cool down. Topped off the rad with water, drove 350 miles home on Sunday without a hiccup. Been driving it since I got home, hasn't happened again, yet.
So, I'm thinking, blown head gasket, cracked head, or cracked block. Exhaust gas getting into the coolant and over pressurizing the cooling system. The parts store 20 lb cap, held it until it let go and just blew a single big burp of coolant, depressurizing the system and causing an overheat. The new 18 lb cap, is doing it's job and venting steam to keep the system not over 18 lbs and so no overheat. All pretty much wild ass guess.
Today, did a pressure leak down test of the radiator. Held steady. No leak down. Used a "block tester" to check for exhaust gas coming out of the coolant. Zero, nothing, nadda. Both test results would indicate, NOT a head gastket.
But! This issue is definitely intermittent. I'd like to see how those tests would go while it's gurgling bubbles from the radiator into the over flow bottle. I suspect, they'd be different.
So - is there such a thing as an intermittent head gasket leak? Have any of you ever encountered that? I'd think a cracked head or block, would not be intermittent. But could a leaking head gasket be intermittent?
My next step, I guess, is pull plugs. They are new, went in just before this trip, have only about a thousand miles on them. I inspected the old ones and saw nothing unusual. While the plugs are out, I'll bore scope to look for indications of washing on the pistons. I'll probably pull the valve cover and check the head bolt torque.
I can do compression and leak down tests, but with the intermittent nature of the issue, I'm not sure I want to bother when the issue isn't manifesting itself. I'm going to keep the block tester in the Jeep and if it happens again, try to test for exhaust gas in the coolant system while it's gurgling into the over flow.
Any other ideas any of you have? For what it might be, or how to continue to diagnose?
Doing the head gasket isn't a huge, huge deal, but it's more than I really want to eff with just on a hope and a prayer. Especially since, if I don't see an obvious problem with the gasket, I'll be having the head magnafluxed and checked for warp/resurfaced just on GP, before bolting it back on.
- DAA
Trying to diagnose an issue with my '06 LJ, Jeep 4.0. Could use some thoughts...
Twice, over about a month this summer, the radiator let loose with a sudden blast of coolant out of the cap. Once about a minute after turning it off and the other time while driving. And the engine immediately overheated both times. But was not overheating, before the cap vent. My guess, the sudden depressurization caused the sudden overheat. But, I actually don't have a clue.
Both times, stopped, took the cap off, let it cool down. Started it up and the problem was gone.
So I replaced the cap. The old one was a 20 lb parts store cap. I've had cruddy luck with parts store parts the last couple of years. So I ordered a Mopar cap, which is the correct 18 lb. Drove close to 2,000 miles without a hiccup and thought life was good.
This weekend, after almost three days of driving, over 600 miles total, about half offroad. The cap started to steam and "spritz" coolant. Not a violent eruption like with the previous 20 lb cap. Mostly just steam, and just enough coolant to make my windshield a mess (my hood has a vent just above the fan). But, the engine wasn't over heating. Temp was running like maybe 4 degrees warmer than usual, but holding steady there.
Stopped, took the cap off, let it cool down. Started it up and the problem was gone.
Next day, it started up again, worse on the steam and coolant spritz out of the cap. But the engine still wasn't overheating. But, while stopped and letting it cool, it was gurgling bubbles out of the radiator into the overflow bottle.
Stopped, let it cool down. Topped off the rad with water, drove 350 miles home on Sunday without a hiccup. Been driving it since I got home, hasn't happened again, yet.
So, I'm thinking, blown head gasket, cracked head, or cracked block. Exhaust gas getting into the coolant and over pressurizing the cooling system. The parts store 20 lb cap, held it until it let go and just blew a single big burp of coolant, depressurizing the system and causing an overheat. The new 18 lb cap, is doing it's job and venting steam to keep the system not over 18 lbs and so no overheat. All pretty much wild ass guess.
Today, did a pressure leak down test of the radiator. Held steady. No leak down. Used a "block tester" to check for exhaust gas coming out of the coolant. Zero, nothing, nadda. Both test results would indicate, NOT a head gastket.
But! This issue is definitely intermittent. I'd like to see how those tests would go while it's gurgling bubbles from the radiator into the over flow bottle. I suspect, they'd be different.
So - is there such a thing as an intermittent head gasket leak? Have any of you ever encountered that? I'd think a cracked head or block, would not be intermittent. But could a leaking head gasket be intermittent?
My next step, I guess, is pull plugs. They are new, went in just before this trip, have only about a thousand miles on them. I inspected the old ones and saw nothing unusual. While the plugs are out, I'll bore scope to look for indications of washing on the pistons. I'll probably pull the valve cover and check the head bolt torque.
I can do compression and leak down tests, but with the intermittent nature of the issue, I'm not sure I want to bother when the issue isn't manifesting itself. I'm going to keep the block tester in the Jeep and if it happens again, try to test for exhaust gas in the coolant system while it's gurgling into the over flow.
Any other ideas any of you have? For what it might be, or how to continue to diagnose?
Doing the head gasket isn't a huge, huge deal, but it's more than I really want to eff with just on a hope and a prayer. Especially since, if I don't see an obvious problem with the gasket, I'll be having the head magnafluxed and checked for warp/resurfaced just on GP, before bolting it back on.
- DAA
