How to tell if a head gasket is blown


snake

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Got a friend with a 2004 F-150 equipped with a 5.4 gas burner. It overheated the other day, and the shop they took it to said "they thought" it was a blown head gasket, and dig this- they want $3800 to fix it.

I've got quite a bit of engine experience, and have seen head gaskets leak internally, externally, combinations of both and I've heard of head gaskets causing overheating- but how would you be damn sure that is what's wrong with it? I haven't seen the truck yet, but I'm sure I will be the one who has to fix it, and I want to be sure before I take it apart. The truck only has a bit over 100K so I seriously doubt this is the problem, and it sounds like the shop is guessing at this. In fact, the way it sounds to me the temp sensor is falsely reading because the gauge is the only thing indicating that it is running hot. Also, it isn't losing water, steaming, going into the oil pan or any other indication that the gaskets are going bad, and no gunk in the coolant either.

All advice is appreciated.
 
Pressure testing the cooling system would be a good place to start. If it got really hot once and warped a head (they are aluminum) I could see the head gasket letting go, but short of running out of coolant it shouldn't cause it to overheat on its own.

I would question the sender too, you shouldn't be out too much if it was right anyway. A temporary mechanical guage should help you find out what the temp really is as well if the sender is expensive. If you pop the hood you will see why they want that kind of money to fix it, and they are probably figuring on the head being trashed too.

If it was getting really hot it should go into limp mode however, where they cylinders take turns firing to help cool the engine, after so long of that it should shut itself off before anything really bad happens.

If you do have to pull the head(s), go ahead and change the spark plugs if it hasn't been done yet (or recently). There is a TSB out about how to do it, they have a nasty habit of letting carbon build up and snapping the tip off in the head when you remove them.
 
Leakdown tests are easier to interpret. As is finding coolant in the crankcase (not all head/head gasket breaches go into a cylinder).

But if any mechanic claims they can rule out a cracked head without removing it from the engine, find another mechanic.
 
$3800?

I'm almost willing to bet that your local Ford dealer will install a factory replacement engine AND warantee it for less than that....

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AllanD said:
$3800?

I'm almost willing to bet that your local Ford dealer will install a factory replacement engine AND warantee it for less than that....

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Click to expand...

we had a 302 put in by ford into my dads 96 f150 for $3000 and it had a 3 year 80,000 mile warranty. $3800 sound way to high.
 
Il install brand new head gaskets and clean up the motor and do it for 2500 :D.
 
put a paper towl over the spark plug hole
have somone hold it(or have someone turn it over 8 revolutions(for a v8))
if there is antifreeze on the towel you either have a bad gasket or a cracked cylinder

iv seen a good head gasker and a cracked cylinder(if it is cracked it will have ok compression if not its the gasket)
 
most of the ones i have seen there is cases of antifreeze in the oil might check the oil that might tell you something
 
Ok, wait, so they want him to shell out almost 4K, just because of the reading on the GUAGE!

I would put a mechanical temp guage on it and see what it reads.

The 5.4L are a LOT more prone to spit a plug than they are to crack a head or blow a gasket. These motors are in almost everything, and that is not a common complaint.
 
Jspafford said:
The 5.4L are a LOT more prone to spit a plug than they are to crack a head or blow a gasket. These motors are in almost everything, and that is not a common complaint.
Click to expand...

The 2V engines are prone to ejecting a plug, the 3V's break off apoun removal if you don't follow the correct procedure.
 
Recently changed the headgasket on my Jeep. Only indications were steam in the exhaust, and low oil pressure. No coolant in the oil, and the coolant was slightly oily feeling. No bubbles in the coolant. No discloration on the plugs. And plenty of power.

Blown headgaskets present themselves in a lot of ways.
 
A blown head gasket--I dunno. It seems to me that when a head gasket fails, something else causes it. Providing it was installed correctly. Overheating causing warping is a biggie. Or on an overhaul the machined surfaces were not milled flat. I would not pay for a head gasket replacement because more often than not, whatever caused it will do it again and you've thrown away a small fortune.

Think about it--these two parts are clamped together under tons of force with a gasket between them. I'm guessing there's something like 30,000# of force per cylinder holding the gasket sealed--8,000# per bolt-ish. It's hard to see the gasket caught between them moving anywhere or even being suseptable to deterioration unless something else fails around it first.
 
Ya- thanks for the replies. Another shop I hang out at said there were some faulty water pumps put on these trucks and they'd seen two or three where the impeller worked loose or broke. I've never seen a water pump do anything but leak, but a pump is a lot cheaper than pulling the heads, worth looking into. They have never seen a head gasket blow on ANY 5.4 to date...

This engine was bought new and never touched, and it didn't really overheat- it just got hotter than normal on the gauge (like 80%). If the engine was bad, I found a long block with all new parts for $2200 and she would end up paying less money and have a new engine, not a worn one with 100K and something a yutz mechanic has been tinkering with. I still betcha it ain't the gaskets...

Thanks for the replies, I'll update everyone if there is anything to report.
 
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