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Scratching my head...

koda2000

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I'll apologize for the length of this post in advance.

A friend of mine has a 2002 4.0L SOHC Explorer. Last summer he overheated it and it developed a small head gasket leak. This leak did not result in coolant in the oil, or oil in the coolant. It seems to just be that it leaks a small amount of exhaust into the cooling system. After running the engine, if you released the pressure from the radiator cap (he has one of those rad caps with the pressure release handle) you can see and hear the bubbles in the coolant reservoir. This only seems to occur until the engine warms up, then the bubbles in the coolant reservoir will stop and all was well. The engine runs fine. He's been driving the vehicle like this for months with no problem.

Now that it's gotten much colder outside (high teens-mid 20's) it appears the exhaust leaking into the cooling system is much worse until the engine gets up to temp. Also, what's now happening is that the radiator pukes a large amount of coolant into the reservoir (sometimes enough to overflow it) and then the temp gauge drops, as does the heater output. If he can manage to get the engine up to temp the exhaust leak stops and everything's fine until the engine gets cold again.

At my advise he's replaced the thermostat, as I reasoned it might be sticking closed, but doing this did not help. Now I'm thinking that the more excessive amount of exhaust getting into the cooling system when the engine's cold is forcing the coolant out and leaving the temp sender/sensor dry. That explains the temp gauge drop, the loss of heat and the overflowing reservoir. The expelled coolant is not hot (just warm) so while the engine could and may overheat without the temp gauge spiking, overheating doesn't seem to be the reason for the expelled coolant.

Other than replacing the head gaskets (and likely at least one head) does anyone have a suggestions as to what he might try? I know he doesn't want to put a ton of money into this vehicle. He's asked me about trying a head gasket sealant, but as it's exhaust leaking into the coolant I don't see any way of expecting a head gasket sealant to work.

If it can be determined which cylinder is leaking exhaust, maybe you could remove the spark plug, unplug the fuel injector and run the engine through a few heat cycles to try to get sealant into the leaking head gasket...?

Any thoughts? Suggested products?
 



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Did he ever figure out what caused the first overheat? As you know, these things don't just overheat without something afoot in the cooling system.
 






Did he ever figure out what caused the first overheat? As you know, these things don't just overheat without something afoot in the cooling system.

Stuck thermostat. He's not much on PM.
 






Stuck thermostat. He's not much on PM.

To be fair.... I use thermostats until they fail.
If they do fail, I've had all but 1 on a Ranger fail in the open position.
Gotta keep 1 eye on yer gauges, lol.

As for the original problem, I have no idea.. I doubt magic in a bottle will fix it though. You already know the solution that truly needs to be done.. New parts and elbow grease.
 






The exhaust gas entering the cooling system at a higher pressure will purge some coolant resulting in overheating from loss of coolant.

The temp gauge doesn't read the coolant temp if the coolant goes below the sensor.
I had this happen just recently.

As you know, this won't fix itself and will only get worse.
The oil and coolant will eventually exchange causing serious problems.
And you know it won't happen in the convenience of his driveway.

I recently had a small leak allowing oil into the coolant and exhaust gas once it had warmed up.
Fixed it with a $10 bottle of Rislone. Not my preferred fix but I will be buggered if I'm going to pull the heads at this stage.

There's an Aussie company that reckons their product is guaranteed to fix leaks at under $100AUD.
They give exhaustive instructions on the website how to locate the leak by pulling spark plug leads then how to apply the product.
http://liquidintelligence.com.au/products/blown-head-gasket-repair
There's some good information there even if you don't use their product.

The detection method didn't work for me so I risked $10 on the Rislone.
 






Well, I'm thinking he might as well try a "Hail Mary" fix in a bottle if he can determine which cylinder is blown, remove the spark plug and deactivate the fuel injector to apply it. The odds are not great this will get him to Spring, but what the heck. If he wants to keep the truck (it's in really nice condition and I know he likes it) I'm going to suggest he look for a relatively low mileage '05 Mustang 4.0L SOHC and do an engine swap. In the long run it'll be cheaper than buying a new/newer vehicle. He has another vehicle he can drive in the mean time if necessary.

Thanks for confirming what I already knew.
 






Personal Testamone

The magic in a bottle does exist, it is called Bars Leak Head Gasket & Cooling Sealant, I bought it at Advance Auto Parts for $44.99 because I had an old 1990Jeep Cherokee that had nearly 400K miles and I did not want to tear the head off to fix this issue which was basically the same as yours. This engine has been running for about 3 years since and has had no further coolant lose and is running very well. Your car is the best candidate for this stuff because it only leaks under certain conditions, meaning it is a very minor leak. Try it you will be amazed.
Mike
 






The magic in a bottle does exist, it is called Bars Leak Head Gasket & Cooling Sealant, I bought it at Advance Auto Parts for $44.99 because I had an old 1990Jeep Cherokee that had nearly 400K miles and I did not want to tear the head off to fix this issue which was basically the same as yours. This engine has been running for about 3 years since and has had no further coolant lose and is running very well. Your car is the best candidate for this stuff because it only leaks under certain conditions, meaning it is a very minor leak. Try it you will be amazed.
Mike

It's worth a try and a lot cheap (and easier) than replacing/rebuilding the engine with around 250k on it. He's got nothing to lose. The first step will be to ID the offending cylinder. For that he'll need to start with a compression test and/or a leak-down test on a stone cold engine. Thanks.
 






Years ago I had a 400 Pontiac that had freeze plugs that were rusted through and leaking severely.

I put Bars Leak through it and it stopped leaking for 1 1/2 years.

It's worth a try.

MT
 












Koda I have the same problem on my 2000 Taurus with the Vulcan engine. I parked it last year because of this. It still runs absolutely perfect but I just couldn't consider it to be a reliable (or salable) vehicle. You are correct the sealants won't work (compression >160psi vs. cooling system @ 16psi). I tried the sealer it did nothing but make a mess. I guess I'll trade it in on another Explorer someday :-)
 






Koda I have the same problem on my 2000 Taurus with the Vulcan engine. I parked it last year because of this. It still runs absolutely perfect but I just couldn't consider it to be a reliable (or salable) vehicle. You are correct the sealants won't work (compression >160psi vs. cooling system @ 16psi). I tried the sealer it did nothing but make a mess. I guess I'll trade it in on another Explorer someday :-)

RE 160 PSI vs 16 PSI... That's why it's so important to ID the leaking cylinder, remove the spark plug and disable the fuel injector before putting in a sealant. Then it's 16 PSI vs near nothing. I'm also considering using a cooling system tester/pump to make sure we get as much pressure as possible in the cooling system (I think a max of 20 PSI should be safe) as 16 PSI is where the radiator cap allows pressure to be released to the reservoir and not the achievable operating pressure.

BTW, I reconfirmed how my friend overheated his engine. It wasn't a stuck thermostat, it was a leaky radiator that caused a low coolant level and the overheating. I tell my daughters to NEVER keep driving if the temp gauge spikes for this reason. My eldest daughter and her husband already destroyed a Honda Civic engine by not pulling over when a hose blew.

In any event, we wont be doing anything until outside temps improve to at least the mid 50's. My thin southern blood doesn't like temps in the teens/twenties... LOL.
 






A stop leak might fix it, but my money is needing a new head.

Don't waste too much of your time on this. I've learned the only way people will learn is if they pay for it. If you help him source cheap parts and work for free, you're only encouraging him to not keep cars in good shape and continue ignoring gauges.

Good luck!
 






it stops bubbling once its warmed up?

try checking the cheap rubber hose between the radiator cap and the coolant reservoir.
if that hose leaks the radiator will suck in air as the engine cools off. then that same air gets pushed back out as the engine heats up and coolant expands.
a bad radiator cap can also do this.
test kits are available to check the coolant for exhaust gas.

if you do have to pull the head and find its warped, getting the surface cut to true it up will only fix the head surface. the top of the head where the cam saddles are is also warped. cam saddles out of line can cause cam breakage.


Perry
 






it stops bubbling once its warmed up?

try checking the cheap rubber hose between the radiator cap and the coolant reservoir.
if that hose leaks the radiator will suck in air as the engine cools off. then that same air gets pushed back out as the engine heats up and coolant expands.
a bad radiator cap can also do this.
test kits are available to check the coolant for exhaust gas.

if you do have to pull the head and find its warped, getting the surface cut to true it up will only fix the head surface. the top of the head where the cam saddles are is also warped. cam saddles out of line can cause cam breakage.
Perry

Radiator is new, cap is new, t-stat is new, hose to reservoir is good. There is no doubt in my mind that the head gasket is leaking exhaust into the cooling system. You can smell the exhaust in the coolant. I would not replace a head gasket on an SOHC engine with high miles. It's not worth it. If a sealant doesn't work and he doesn't want to replace the engine, this truck will be sold for parts or scrap, which IMO would be a shame.
 






Wanted to tell you I just 2 weeks ago used Blue Devil in my explorer with the same exhaust gas to radiator. It worked in mine. Very pleased. They have two type the pour and go I don't think worked but the slightly more expensive professional product worked nicely. O'Rielys had it on sale. Follow the directions and if you have a cap less radiator put all the product in the upper radiator hose then start the vehicle.
 






Wanted to tell you I just 2 weeks ago used Blue Devil in my explorer with the same exhaust gas to radiator. It worked in mine. Very pleased. They have two type the pour and go I don't think worked but the slightly more expensive professional product worked nicely. O'Rielys had it on sale. Follow the directions and if you have a cap less radiator put all the product in the upper radiator hose then start the vehicle.

Do you have to drain the antifreeze before or after you use one of these products?
 






Just from memory the Blue Devil Pro directions are.

1. Drain coolant
2. Remove Thermostat
3. Flush system with appropriate coolant system flush
4. Fill system with plain water
5. Pour in product slowly. OR if no radiator cap pour in upper hose all at once
6. Crank engine and turn on heat
7. Let run for 50 minutes

OR the Blue Devil pour and go is just that, pour it in and let it idle for 50 minutes.

Pour and go did not work for me but I did some other things after I put it in and may have messed something up.

Pour and go about $40
Pro about $55

From what the guy said on their info line I called these products do not have granules or other particulates but rather a chemical that reacts at the site of the leak due to heat.

I also believe that they offer a 100% money back guarantee if it does not work for you.
 









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Koda I have the same problem on my 2000 Taurus with the Vulcan engine...I guess I'll trade it in on another Explorer someday :-)

Do it sooner rather than later. Those engines perform great, but the transaxles are notorious for having ****ty torque converters. My sister's 2000 Taurus stripped the splines out of the torque converter at 75,000 miles, leaving her stranded.

The splines are literally cut into a washer that's tack welded to the converter body. Cheap as *^%$.
 






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