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Updated 12/26 : Head gasket or not?

Hello I’m trying to help a friend with a 2000 Honda Passport with just over 150,000 miles… It’s been diagnosed as having a bad head gasket by a mechanic, although other then the overheating it’s not showing any signs. What I mean is that the oil is clean, there is no smoke, there is not extra pressure in the crank case or the radiator. Also, no bubbles in the radiator.

What it does do is run at a good temp at idle but as soon as you try to drive it (I did not make it two blocks) the temp spikes right away.

I also noticed the clutch fan is not pulling much air, but I was running the ac (so the condenser fan was on) and had the heat set to high…

Plus the radiator is new as well.

So how can I verify the head gasket is bad??


This is what you need to use

If the fluid turns yellow, you’ve got major problems

Did the mechanic just guess based on the fact of overheating? Because you’re saying there are none of the typical signs of head gasket failure. So the first question to ask is, exactly how did the mechanic determine that the head gasket is leaking?

If the mechanic didn’t do it, the coolant can be tested for hydrocarbons.

And there are other possible explanations for the overheating. For example, a bad water pump with eroded vanes will cause overheating, and this seems to be one of the most overlooked potential causes of overheating.

So do NOT just assume a head gasket leak. If the hydrocarbon test comes back negative. It’s not leaking. And you can buy a test kit yourself at an auto parts store.

Did the overheating start after the new radiator or is the new radiator the result of overheating? Has the system been bled properly? Did the new radiator come with a new radiator cap, of not, did anyone replace the cap?

Both fans have to work when the AC is on, if not, that has to be addressed, however, with the AC off, the engine should not overheat when the vehicle is moving.

There is a recent thread at a Saturn site that I visit where the owner had just replaced the radiator due to a leak. Then he had overheating problems just like yours. Turns out that there was a plug inside one of the radiator bungs that he did not see when he installed the radiator.

Gotta agree with the others to check the diagnosis. The only head gasket problem I had it would spike at low RPM but be ok at high RPM. Had no water in oil or smoke either but many bubbles and pressure in the radiator.

Keith the story I was told was his kid was driving it and smoke started coming from the hood, he got it home and it was very hot… The rad had cracked at the top tank by the neck… They replaced it and the cap, and the truck still overheated so they took it to a mechanic who said head gasket… I don’t know how he diag it… However I can tell you the clutch fan has almost no resistance and was not pulling much air when I had it running the other day… I just picked up the coolest tester so we will see what it says. I am hoping for the best.


Welcome back, CSA!
Where have you been?


Any chance “the kid” is somehow responsible for the blown headgasket?

It wouldn’t be the first time that “a kid” grudgingly admits that he drove the snot out of the family car and caused something to fail . . .

I think it is good that you did not jump right onto the headgasket. It seems that a lot of mechanics are quick to make this judgement. It is good that you are testing it first.

Yeah Keith, that’s my hope… I actually just had it dragged (behind my friends f250) to my house as I have lots of tools… It was about a 5 mile drag (took about 10-15 min as we were going slow). I had the motor running the whole time (so I had power steering and brakes) and it was staying perfectly cool… I can smell antifreeze, but I’m still thinking it’s not the head gasket. Waiting for it to cool down so I can drain the radiator a little and test it… Will post the results later, I hope.

Ok just got back in, and its blue !!! I even checked the fluid by taking some sniffs of the exhaust and it turned yellow… Lol

So now its a game of what’s the problem… One thing it did do today while testing was percolate which it has never done to me before… It started pushing antifreeze out the radiator (remember the cap was off) I quickly put the cap on and I could hear what can only be described as percolating… I went to re test and it did it again… Both times this percolation lasted about a min after shutting the car off. The temp gauge was still at half way I did check. Also of note is my drive way is at an angle and the car was pointing up if that makes a difference.

So what do you guys think, I think at least clutch fan maybe water pump as well… Radiator is new, cap is new… Thoughts ??


Gas percolating into the radiator and pushing antifreeze out is a sure sign of a head gasket breach.

I don’t think so in this case, the cap was off and I had run the truck for 15+ Min earlier today with no issues.

It’s hard to see how there could be a head gasket leak when the coolant test came out negative. Maybe the percolation is due to a trapped air bubble somewhere in the system. Have you tried bleeding the cooling system?

I would still tend to suspect the water pump or something that’s impeding coolant flow. Also, though I’ve never seen it myself, I’ve heard that hoses can sometimes collapse internally and cause a blockage that’s not visible from outside.

Another quick and dirty test you can do is to rubber band a plastic bag over the filler neck with the cap off. Run the engine and see if it inflates.

If the fan clutch is as bad as you describe that may very well be the cause of the “percolating” you describe. I would replace the clutch and install a new thermostat if the shop that replaced the radiator didn’t already do so. Then fill and bleed the cooling system and hope for the best.

A couple of notes:
The fluid tester is great at finding head gaskets that are quite bad, but not always reliable to detect a marginal breach. @jesmed describes another method used sometimes, though I use a latex glove. Pinch off the overflow hose, rubber band a glove over the neck, and start the engine. If it inflates within a few minutes, another strike against the head gasket.

Even if you fix the overheating now, you may not be out of the woods yet. Sounds like it was overheated pretty badly, could have weakened the gaskets. In my experience these Isuzu engines are not particularly stout when it comes to overheating.

In my expierience, the only time an engine overheats that quickly when under a load is because a breached head gasket.


Then why would it pass the block test?? I did it twice to confirm, and it passed both times??

Head gaskets can fail in many funny ways.

I had I think an 85 Civic that displayed the exact same symtoms. Let it idle and it never overheated. As soon as it was driven, the temp gauge peg’d out.

It was the head gasket.


The percolation could simply be due to the lack of pressurization with the cap off. Have you ever taken a radiator cap off of a running but moderately hot engine, and then shut it off? It will usually boil over and do a pretty good impersonation of Old Faithful in short order. Of course pulling the cap off of your engine after it has gotten very hot is risky, but doing the sniffer test under those conditions would be a good determining factor.

Has the water pump ever been replaced? I’d lean toward a bad impeller.