Head gasket? Cracked intake? HELP!!!!

zb99gt · Mar 6, 2009

im new to the forums, i have a 99 gt and was wonderin if you guys could help me diagnose my problem. i just bought the car and noticed the heat wasnt very hot so i checked my antifreeze and the tank was empty. went to fill it and noticed some brown paste looking stuff on the walls of the inside of the tank like the guy that owned the car before me may have put bars leak in it. i filled the tank and the heat started workin fine again but now the antifreeze will like boil over and push out around the cap as soon as it gets to normal running temperature. the car doesnt overheat, it always stays within normal range almost right in the middle of the gauge. ive heard the 4.6's rarely go through head gaskets and that alot of times its a cracked intake. has anyone had a problem like this? any help appreciated!! thanks
*forgot to add that theres no antifreeze mixing with the oil*

SONIC02 · Mar 6, 2009

Did you try a new cap?

zb99gt · Mar 6, 2009

no didnt do that yet il try that tonight.

eliteJAE · Mar 6, 2009

I had the same exact symptoms, I had a bad head gasket, it eventually blew.

Don't trust the temp gauge they're dummy gauges and don't react to changes very well.

Do you know how to get into the diagnostic mode in the odometer screen? It shows temps in real time. You definitely have a bad head gasket or intake gasket, sounds like a head gasket to me. Whenever it starts spewing coolant out of the rad, check the temp in diagnostic mode and it'll probably be high.

Don't run the car too hard and check the coolant often, I didn't know anything when it happened to me, but you're describing everything that happened to me.

Pm me if you need more info, people say the head gaskets don't fail much on 4.6's but mine sure did and I have experience with it lol I tried evry other thing you can think of to stop the coolant from gushing out, including a new cap, nothing worked until I replaced the bad head gasket when it blew.

zb99gt · Mar 6, 2009

dang, yea im not sure how to get it into diagnostic mode il look it up thanks for the help

MustangLife · Mar 6, 2009

It might be the head gasket/intake gasket. But always look for the best case scenario first. For something like that don't expect the worst and assume that. Coolant spewing out of the top. Like what was said earlier. It is a 9 year old car, its not new anymore. It could be the original radiator cap. Change that first, its a cheap part. 2nd the radiator could be clogged up, hince the brown goo you saw. Sounds like the guy probaly never had the radiator flushed. Your system needs a good flush. I had a car about 10 years ago with a clogged up radiator. It needed to be rodded out. I eventually just bought a new factory radiator for like $130 or something like that. Hope this helps

eliteJAE · Mar 6, 2009

to get into diagnostic mode, push and hold the odometer reset button without the key being in the ignition, then as youre golding the button put the key into the ignition and turn it to the ON position, right before actual crank, where all the accessories turn on, and it should make the gauges sweep after some seconds.

after the gauges sweep, youre in the diagnostic mode, and you cant let go of the odometer reset button. now just push and release the odometer reset button t cycle through the menu.

GDawg · Mar 7, 2009

Could be the common problem of cracked intake manifold that happened to a lot of our plastic manifolds through 2000. Do you have the plastic coolant runner?

GT Tommy · Mar 7, 2009

Coolant boiling over!

zb99gt said:
im new to the forums, i have a 99 gt and was wonderin if you guys could help me diagnose my problem. i just bought the car and noticed the heat wasnt very hot so i checked my antifreeze and the tank was empty. went to fill it and noticed some brown paste looking stuff on the walls of the inside of the tank like the guy that owned the car before me may have put bars leak in it. i filled the tank and the heat started workin fine again but now the antifreeze will like boil over and push out around the cap as soon as it gets to normal running temperature. the car doesnt overheat, it always stays within normal range almost right in the middle of the gauge. ive heard the 4.6's rarely go through head gaskets and that alot of times its a cracked intake. has anyone had a problem like this? any help appreciated!! thanks
*forgot to add that theres no antifreeze mixing with the oil*

Sounds to me like your thermostat is not openning far enough. I would start with replacing it! Or temporarily remove it to see if the coolant still boils over. If after you remove it your problem goes away, then you will know that your thermostat is the problem. It may be a good idea to go with a 180 degree thermostat when you replace it. Good luck, Tommy.

zb99gt · Mar 7, 2009

GT Tommy said:
Sounds to me like your thermostat is not openning far enough. I would start with replacing it! Or temporarily remove it to see if the coolant still boils over. If after you remove it your problem goes away, then you will know that your thermostat is the problem. It may be a good idea to go with a 180 degree thermostat when you replace it. Good luck, Tommy.

il try that tomorow, i was gonna buy a new cap but fords not open until monday so i think im gonna try the thermostat thing tomorow and flush the system too. thanks for the help

zb99gt · Mar 7, 2009

GDawg said:
Could be the common problem of cracked intake manifold that happened to a lot of our plastic manifolds through 2000. Do you have the plastic coolant runner?

yea it has the plastic coolant runner. today i looked down by the intake and could see that there was some sort of liquid sitting under the intake (probably antifreeze). so i think its time to start tearin it down and just look for cracks if its not the thermostat or clogged radiator

GT Tommy · Mar 7, 2009

Coolant leaking around intake manifold!

I don't want to alarm you, however, I just replaced my son's intake manifold. It was leaking coolant just behind the thermostat housing base. The pictures provided here, are of the actual intake which I removed from my son's 2003 GT Mustang 4.6 engine. The 1st picture is of the bottom view of the intake manifold, specifically of the thermostat housing base. You can see where the O ring is not seated where it belongs. This caused the coolant to leak through the base of the thermostat housing. To check if your coolant is leaking in the same area, you have to fill your reservoir to the full mark, then start your engine and watch and look for coolant leaks. Look just behind the thermostat housing base. You may need a flash light to see the coolant leaking out in that area. It's just a small gap there, so you have to look good. The 2nd picture is also the bottom view of the passenger side of where the aluminum channel cross over piece bolts to the intake manifold. As you can see, the O ring gasket was not seated properly in that location as well. Make sure you click on the pictures to make them larger. I have read of numerious Mustang 4.6 intake coolant leaks in this same locations. It is quite possible, that you have a leak in the same area. The coolant would leak and end up in the valley below the intake manifold. The coolant would also leak and run towards the back of the engine, giving a false impression that there was a leak at the back of the engine as well. However, it was leaking mostly at the thermostat base, where the aluminum base sits on the plastic portion of the intake manifold. Hope this is not the case for you, but, it's good to check it out. The reservoir has to be full for you to see the coolant leak in the thermostat area. Once the reservoir is empty, the coolant will not longer leak in that area, because of the height difference between the two locations. Check it out and let the rest of us know what you find. Good luck, Tommy.

zb99gt · Mar 7, 2009

GT Tommy said:
I don't want to alarm you, however, I just replaced my son's intake manifold. It was leaking coolant just behind the thermostat housing base. The pictures provided here, are of the actual intake which I removed from my son's 2003 GT Mustang 4.6 engine. The 1st picture is of the bottom view of the intake manifold, specifically of the thermostat housing base. You can see where the O ring is not seated where it belongs. This caused the coolant to leak through the base of the thermostat housing. To check if your coolant is leaking in the same area, you have to fill your reservoir to the full mark, then start your engine and watch and look for coolant leaks. Look just behind the thermostat housing base. You may need a flash light to see the coolant leaking out in that area. It's just a small gap there, so you have to look good. The 2nd picture is also the bottom view of the passenger side of where the aluminum channel cross over piece bolts to the intake manifold. As you can see, the O ring gasket was not seated properly in that location as well. Make sure you click on the pictures to make them larger. I have read of numerious Mustang 4.6 intake coolant leaks in this same locations. It is quite possible, that you have a leak in the same area. The coolant would leak and end up in the valley below the intake manifold. The coolant would also leak and run towards the back of the engine, giving a false impression that there was a leak at the back of the engine as well. However, it was leaking mostly at the thermostat base, where the aluminum base sits on the plastic portion of the intake manifold. Hope this is not the case for you, but, it's good to check it out. The reservoir has to be full for you to see the coolant leak in the thermostat area. Once the reservoir is empty, the coolant will not longer leak in that area, because of the height difference between the two locations. Check it out and let the rest of us know what you find. Good luck, Tommy.

thanks for all the info tommy, il try what you said tomorow morning. was your sons mustang pushing the antifreeze out of the overflow?
thanks alot

GT Tommy · Mar 7, 2009

Additional Info on the Edelbrock Intake Manifold!

Yes, at one time, his coolant was backing up wanting to come out from the reservoir cap. Then not long after that is when he noticed that he had to consistantly fill his reservoir with coolant. That's what made him look for a leak. And he finally found the leak behind the thermostat housing base. Here is a link I just found concerning the Edelbrock intake. Looks like this one can be used for fuel injected engines as well. Check it out. Yes, let me know if you find any coolant leaks. Check your dip stick as well. If your oil is of a creamy color, that is not good! My gut feeling is you have the same type of leak my son's engine had. Good luck, Tommy.

Ford 4.6L EFI intake manifold Edelbrock 28385 Victor Jr. EFI

GT Tommy · Mar 7, 2009

Mustang Intake Coolant Leak!

I wanted to share another picture with you all. This picture is from someone else that I met on the internet. He has the same exact coolant leak that my son had on his intake manifold. It is in the same exact area. Notice the O ring is damaged. Also notice that the plastic coolant port has melted downward. You know, the more I think about it, the more I think the culprit is a defective thermostat that is causing the leak around the thermostat housing base, as well as a design flaw. If the thermostat is stuck in the closed position, the coolant then gets trapped inside the engine, it has to go somewhere, it then forces the O ring out of position causing a coolant leak in that area. This makes sense. The water pump will constantly pump the coolant up to the thermostat, and if the thermostat does not open, because it's stuck for what ever reason, then the nearest weak point will give way, which is the O ring seal at the base of the thermostat housing. There has to be a design flaw in that area. The plastic intake at the base of the thermostat housing where the O ring sits, is only 1/2" thick. When ever the thermostat freezes up, the plastic intake at the O ring seating surface probably gets so hot, that it becomes soft (like in the picture provided) which would then allow the O ring to move from it's seating surface causing a coolant leak in that area. That has to be it! Well, that's how I see it anyway! Something to think about. Good luck, Tommy.

zb99gt · Mar 7, 2009

GT Tommy said:
I wanted to share another picture with you all. This picture is from someone else that I met on the internet. He has the same exact coolant leak that my son had on his intake manifold. It is in the same exact area. Notice the O ring is damaged. Also notice that the plastic coolant port has melted downward. You know, the more I think about it, the more I think the culprit is a defective thermostat that is causing the leak around the thermostat housing base, as well as a design flaw. If the thermostat is stuck in the closed position, the coolant then gets trapped inside the engine, it has to go somewhere, it then forces the O ring out of position causing a coolant leak in that area. This makes sense. The water pump will constantly pump the coolant up to the thermostat, and if the thermostat does not open, because it's stuck for what ever reason, then the nearest weak point will give way, which is the O ring seal at the base of the thermostat housing. There has to be a design flaw in that area. The plastic intake at the base of the thermostat housing where the O ring sits, is only 1/2" thick. When ever the thermostat freezes up, the plastic intake at the O ring seating surface probably gets so hot, that it becomes soft (like in the picture provided) which would then allow the O ring to move from it's seating surface causing a coolant leak in that area. That has to be it! Well, that's how I see it anyway! Something to think about. Good luck, Tommy.

yea that does make sense. il start tearin it apart tomorow and let ya know if i find anything and maybe take a few pics. thanks for all the help

Killa · Mar 9, 2009

I got exactly same problem, but my a little different, I did PI intake swap on my 98gt with adapter, I dint knew I need 2 set of gasket, 1 is NPI gasket that go on the bottem of the adapter, and PI gasket on top of the adapter, doest your smoke at all ?

GT Tommy · Mar 9, 2009

Engine smoking after intake install?

KillaGT, no, the engine is running really well. No smoke at all. Are you saying that you currently don't have any gasket between the adaptor and heads? If you don't, I would think this is why your engine may be smoking. If you don't have any type of gasket between your adaptor and heads, if I were you I would not run the engine and get the appropriate gaskets for that area and install them right away before you damage your engine. What type of material is the adaptor made of? Is it aluminum? You can't have metal to metal contact. I'm surprised you don't have vacuum leaks as well! You probably have coolant leaking into the exhaust ports. That could be where the smoke is coming from. So, what is your status right now? Thank you, Tommy.

Killa · Mar 9, 2009

GT Tommy said:
KillaGT, no, the engine is running really well. No smoke at all. Are you saying that you currently don't have any gasket between the adaptor and heads? If you don't, I would think this is why your engine may be smoking. If you don't have any type of gasket between your adaptor and heads, if I were you I would not run the engine and get the appropriate gaskets for that area and install them right away before you damage your engine. What type of material is the adaptor made of? Is it aluminum? You can't have metal to metal contact. I'm surprised you don't have vacuum leaks as well! You probably have coolant leaking into the exhaust ports. That could be where the smoke is coming from. So, what is your status right now? Thank you, Tommy.

I only using 1 set of PI gasket on top of the adapter, yes I do have a whisling sound coming from the intake adapter area. about 2 week ago I did learn that I need both set of gasket for the adapter. but when I order my HPS adapter, they told me only using 1 set of PI gasket. and I think I have a very small leak, cause I only add coolant every 2-3 month or so. im currently have alot other thing in life to worried about, I think imma let my machanic doing the intake gasket for me. but im in process selling this mustang soon ( read my other thread ).

GT Tommy · Mar 9, 2009

KillaGT said:
I only using 1 set of PI gasket on top of the adapter, yes I do have a whisling sound coming from the intake adapter area. about 2 week ago I did learn that I need both set of gasket for the adapter. but when I order my HPS adapter, they told me only using 1 set of PI gasket. and I think I have a very small leak, cause I only add coolant every 2-3 month or so. im currently have alot other thing in life to worried about, I think imma let my machanic doing the intake gasket for me. but im in process selling this mustang soon ( read my other thread ).

Yes, you need that gaskets between the adaptors and heads. I don't care what any body says, you need them! The sooner the better. That would take care of your problems. Make sure your adaptor ports line up with the ports on your head. That goes for the gasket that you purchase as well. Your O ring gaskets on the intake side should still be good to reuse. You said you have the PI intake, that is the one with the integrated O ring gaskets on the intake, correct? You probably will need a new set of spark plugs as well. Take care of this problem before you sell the car. You don't want the buyer coming back to haunt you! Do it right! Good luck, Tommy.

Head gasket? Cracked intake? HELP!!!!

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