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Author
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Topic: UPDATE!!!!!...Can't find where leak is coming from 1990 5.0
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Just_a_GT
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Member # 10372
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posted
 
 
A family member has a 1990 5.0. It has an explorer intake. The car was obtained thru a trade with this problem. Originally they thought it was the headers. They replaced the headers with new gaskets and the problem is still there. It's like a loud exhaust leak, air escaping somewhere behind the driver side cylinder head. The car also idles very low like it has an vaccum leak. I haven't had time to examine the car very well but has anyone experienced something like this. I have a feeling it might be something to do with the manifold. I am looking into buying the car and would like to resolve the problem. Just want some input so when I go check te car I an try to fix the problem and drive it home. When I looked at the car a couple weeks back I stuck my hand behind the manifold by the exhaust flange an I could feel the air escaping. Could it be the exhaust still??
[ 2013-10-23, 12:33 AM: Message edited by: GR8WHITE281 ]
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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cemelevu
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Member # 10601
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sounds like a leak at the flange.
Posts: 474 | Registered: Jan 2011
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sleeping stallion
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Member # 8162
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Check the back of the heads where they have the tubes hooked up for smog purposes maybe they took it off
We had a similar problem
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1990 coupe HCI Boost
SEMPER FIDELIS
Posts: 1650 | From: Modesto ca | Registered: Jan 2008
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nasty93
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Member # 8935
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Sounds like an exhaust leak.tighten that shit up.
Posts: 464 | From: windsor ,ca | Registered: Feb 2009
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Wht86drop
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Member # 12104
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Also check the PCV. It could have popped out or the grommet could be bad
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Jalapeña Red 86 GT Vert
Yellow 72 Chevelle
Rio Red 97 Cobra
High-Output Generations CC
Posts: 1669 | From: East Palo Alto, Fiji Islands | Registered: Jun 2012
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92_5.0
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Member # 7624
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posted
quote:
Originally posted by sleeping stallion:
Check the back of the heads where they have the tubes hooked up for smog purposes maybe they took it off
We had a similar problem
I would suspect this to be the case also. There are two 3/8 bolts I believe.
Posts: 1629 | From: bay area | Registered: May 2007
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Just_a_GT
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Member # 10372
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posted
quote:
Originally posted by sleeping stallion:
Check the back of the heads where they have the tubes hooked up for smog purposes maybe they took it off
We had a similar problem
Would this cause the low idle where it almost dies?
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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Just_a_GT
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Member # 10372
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Thanks for the input. Ill update the situation later on.
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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SIC9250
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Member # 8216
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posted
quote:
Originally posted by sleeping stallion:
Check the back of the heads where they have the tubes hooked up for smog purposes maybe they took it off
We had a similar problem
This..
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Coyote_Mach1
Posts: 6959 | From: in the drivers seat. | Registered: Feb 2008
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Just_a_GT
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Member # 10372
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posted
Picked up the car and had some time to diagnose the problem this weekend.
Found the leak is coming from under driver side header port number 3. Could the head be warped ? Driver side header had a mr gasket piece of crap paper gasket that was blown Out on the last port. Switched to a better gasket and the noise did get a little quieter. I'm going to use silicone on the header and see if that stops it. Friend of mine recommended it since he had his 5.0 with straight silicone no gaskets on his headers, never leaked.
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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NK2186
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Member # 12319
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posted
quote:
Originally posted by GR8WHITE281:
Picked up the car and had some time to diagnose the problem this weekend.
Found the leak is coming from under driver side header port number 3. Could the head be warped ? Driver side header had a mr gasket piece of crap paper gasket that was blown Out on the last port. Switched to a better gasket and the noise did get a little quieter. I'm going to use silicone on the header and see if that stops it. Friend of mine recommended it since he had his 5.0 with straight silicone no gaskets on his headers, never leaked.
Sometimes the header flange can get warped. An old man once told me to just cut the flanges on the header if this ever happened. But i would only do this if it was a last resort. try running a copper gasket with some new ARP header bolts.
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90 LX 5.0 - Stolen/stripped
89 LX 5.0 - Stolen and missing as of 7-24-13. LIC# 4HIP151 :(
99 Cobra
00 Exploder
Posts: 400 | From: Haystack | Registered: Aug 2012
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Tom Renzo
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Member # 13165
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We normally cut the header flange between the flanges if possible. Sometimes you can not do this. You have to make sure te flange has individual bolts. Another words for example on a small block chevy we cut twice. One near the front and one near the rear. Reason being there is only 6 bolts holding the manifold. So if for example you have 8 bolts one on each side of the port you can do this.We also use high Temp silicone that is sensor safe to seal them as long as they are good headers and have a machined surface. Thanks and good luck
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I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
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Just_a_GT
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Member # 10372
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posted
My brother in law figured it out. Well it turns out the leak is between the head and the block by cylinder 7. Which makes sense because it is definately an air leak and it definitely sounds like compressed air being pushed out. Put a rag up to where the leak comes from and the noise dies out. So I will be doing a compression test to confirm.
The car does not over heat and the oil does not look like it has water in it. So looks like a head gasket swap is going to fix my issue unless you guys have an alternative fix.. I'm thinking maybe torquing the head down, it might not be all the way seated.
Anybody ever had a similar issue??
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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SacStangDriver
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Member # 8304
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leakdown is better then comrpession
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Need sidework done at great prices? I work on all makes and models from engine work to gears. Check engine light problems too. 916 912 3493
Posts: 1217 | From: sacramento | Registered: Mar 2008
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Tom Renzo
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Member # 13165
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posted
quote:
Originally posted by GR8WHITE281:
My brother in law figured it out. Well it turns out the leak is between the head and the block by cylinder 7. Which makes sense because it is definately an air leak and it definitely sounds like compressed air being pushed out. Put a rag up to where the leak comes from and the noise dies out. So I will be doing a compression test to confirm.
The car does not over heat and the oil does not look like it has water in it. So looks like a head gasket swap is going to fix my issue unless you guys have an alternative fix.. I'm thinking maybe torquing the head down, it might not be all the way seated.
Anybody ever had a similar issue??
NOPE if the head is leaking compression it will be the first time in 48 years i have heard of it. And if in fact it does this i will be the first to be shocked. As far as the head not being all the way flat with the block is another thing that will shock the hell out of me. What is most likely happening is the header is not seating on the head. And or the gasket is blown out between the header and the head. So do your compression test and popst the numbers. If in fact you have a dead cylinder i once again will be lost for words if it is not seating because of a blown head gasket. That will also be a first for me. WOWWWWWWWWWWWW!!!
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I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
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Just_a_GT
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Member # 10372
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posted
^^^^^^^^^^^ I'm stumped too. It's unheard of but I'm positive it's coming from the head and the block . When I put the rag up to the leak I feel the heat coming from the gas burning inside the cylinder. There is noticeable oil that seems to be coming out of that gap where it's leaking.
For sure it is not the exhaust I have ruled that out. I'm positive it's not it.
Did compression test on 5-8
I did the test with the car cold
#5- 115
#6-115
#7- 115
#8- kept jumping around it would go from 70-90-120, then I would purge the tester and it would stay at around 90
I feel the leak between head and block right under exhaust port for cylinder 7, I would have thought cylinder 7 would be acting funny but no it's number 8
I will do leak down test when I get a chance
Any ideas fellas?????
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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Tom Renzo
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Member # 13165
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Dont waste you time leaking it down. Pull the head and post photos. I am o0ne person that wants to see this personally Thanks
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I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
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Just_a_GT
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Member # 10372
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posted
quote:
Originally posted by Tom Renzo:
Dont waste you time leaking it down. Pull the head and post photos. I am o0ne person that wants to see this personally Thanks
Yea that's what im leaning towards. Just doing a rebuild on it.
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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Just_a_GT
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Member # 10372
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posted
Pulled the heads. Driver side gasket is split by cylinder 7. Car ran fine. Drove it home from San Jose when I bought it
I also found one piston damaged because porcelain off a spark plug fell in the chamber
Will post some pictures when I have a chance
I will be pulling the block and doing a rebuild, might as well lol
Might thow in a set of heads and some better pistons
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1990 GT 308 edelbrock alum heads Daily driver
2000 GT CAMMED 281ci
Posts: 697 | From: Winton, CA | Registered: Oct 2010
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Duncan Motors
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Member # 7045
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posted
[ 2013-10-29, 01:37 PM: Message edited by: Duncan Motors ]
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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