how hot until she blows
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
The main fan did come on. I don't have another fan that Im aware of. I did replace the thermostat with a new one before we fired it up. It also has new freeze plugs for what thats worth. We made sure it was full of antifreeze before we started it and did use a 50/50 mixture.
So discoloration in the spark plugs indicates piston wear or just a head gasket leak? There is definitely moisture in the oil....it showed over filled only after the break in and there seems to be coolant coming out of the exhaust. We pulled a valve cover also and there is indication of moisture in the cover as well.
Do you think I am looking at another head gasket job? Do you think it was my temp that caused this or some other problem? This sucks.
So discoloration in the spark plugs indicates piston wear or just a head gasket leak? There is definitely moisture in the oil....it showed over filled only after the break in and there seems to be coolant coming out of the exhaust. We pulled a valve cover also and there is indication of moisture in the cover as well.
Do you think I am looking at another head gasket job? Do you think it was my temp that caused this or some other problem? This sucks.
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
Does the oil look like chocolate milk?If so don't run the engine anymore unless your doing a block test(to see if hydrocarbons are in coolant).If you run the engine with coolant mixed with oil,it can damage all your engine bearings.You may have installed the intake incorrectly causing coolant to leak into engine through the "engine valley".If the block test,tests good(no color change),pull intake & see if anything was installed wrong or theres a crack on/in intake.Once you fix the problem,do a very through coolant flush & flush the engine with a oil flush additive as well.Aluminum engines or headed engines don't handle over heating like a cast iron engine.Keep us updated on what you find
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
some of you may throw up a 
, but my son's 85 hit 296 (dash indicated) due to a water pump failure. new water pump, and she's running okay. ran a compression test, and the readings were around 168, average across 8 cylinders. L98's, at least iron head L98's, are pretty tough little motors.
, but my son's 85 hit 296 (dash indicated) due to a water pump failure. new water pump, and she's running okay. ran a compression test, and the readings were around 168, average across 8 cylinders. L98's, at least iron head L98's, are pretty tough little motors.
Racer
Joined: Mar 2011
Posts: 296
Likes: 0
From: Derby (Wichita area) KS
Ok gentlemen, I don't mean to jack your thread but maybe one of you could shed some light on this for me...
I believe I have a head gasket leak on an 89 which I suspect got hot at some point (how hot I do not know as I just bought the car but it runs fine, sounds good).
no visible water in the oil, does have visible external coolant leak near the # 7 cylinder...drivers side, near the firewall.
Can any of you tell me approximately how many shop hours I'd be looking at to R&R both head gaskets? I already have a quote for machining & a pretty good feel for parts. Reason being I have a friend who offered to do the reapair for me (very skilled professional mech)- when I asked him what he'd charge, he said it was up to me. I value his friendship so I don't want to cheat him but I tend to be a tightwad hence my delima.
Thoughts?
I believe I have a head gasket leak on an 89 which I suspect got hot at some point (how hot I do not know as I just bought the car but it runs fine, sounds good).
no visible water in the oil, does have visible external coolant leak near the # 7 cylinder...drivers side, near the firewall.
Can any of you tell me approximately how many shop hours I'd be looking at to R&R both head gaskets? I already have a quote for machining & a pretty good feel for parts. Reason being I have a friend who offered to do the reapair for me (very skilled professional mech)- when I asked him what he'd charge, he said it was up to me. I value his friendship so I don't want to cheat him but I tend to be a tightwad hence my delima.
Thoughts?
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
Ok gentlemen, I don't mean to jack your thread but maybe one of you could shed some light on this for me...
I believe I have a head gasket leak on an 89 which I suspect got hot at some point (how hot I do not know as I just bought the car but it runs fine, sounds good).
no visible water in the oil, does have visible external coolant leak near the # 7 cylinder...drivers side, near the firewall.
Can any of you tell me approximately how many shop hours I'd be looking at to R&R both head gaskets? I already have a quote for machining & a pretty good feel for parts. Reason being I have a friend who offered to do the reapair for me (very skilled professional mech)- when I asked him what he'd charge, he said it was up to me. I value his friendship so I don't want to cheat him but I tend to be a tightwad hence my delima.
Thoughts?
I believe I have a head gasket leak on an 89 which I suspect got hot at some point (how hot I do not know as I just bought the car but it runs fine, sounds good).
no visible water in the oil, does have visible external coolant leak near the # 7 cylinder...drivers side, near the firewall.
Can any of you tell me approximately how many shop hours I'd be looking at to R&R both head gaskets? I already have a quote for machining & a pretty good feel for parts. Reason being I have a friend who offered to do the reapair for me (very skilled professional mech)- when I asked him what he'd charge, he said it was up to me. I value his friendship so I don't want to cheat him but I tend to be a tightwad hence my delima.
Thoughts?
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
agree with the others, north of 250 is the danger zone. you can fracture the cast top rings and experience oil breakdown. even if you're using redline which could handle the heat the gasket and rings won't. i'm not sure you would really see any skirt or cylinder damage though. cast pistons really don't expand much. if you did it would be from the breakdown in the oil
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Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
unless you have performed a leakdown it's hard to say 100% the top rings in these old engines are cast iron, not tool steel like many modern motors. they can fracture fairly easy
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
That was like 9 years ago. I think I would know by now if something happened. Absolutely nothing happened to the motor.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
it's completely possible that nothing happened but only a leakdown will really tell you
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
I've been driving this car for the last 9 years plus. Oil consumption is normal. I have even compression across all 8 cylinders measuring just a few PSI under 200 on all of them and the head gasket is not blown. I have zero coolant loss.
I have fixed more overheated vehicles where I had to replace valves, rebuild/resurface the warped cylinder heads on them, and in some cases even re-ring and hone the bottom end than I can remember at this time. This isn't my first day. I know what happens to motors when they overheat. I've seen it. I've fixed many. Nothing happened to my car which even surprised me. I was only at 280 ish for a short while. When I popped the hood and noticed the fan was not spinning I got back on the open road to force air through the radiator and brought the temps back down quickly. I avoided driving in traffic until I fixed the fan problem.
The OP asked how how till the head gasket blows on these cars. I can't give an exact answer. What I can say is that I hit at least 280 degrees on the guage at least two times on the same day with mine and my head gasket didn't blow nor did my compression readings change or suffered any engine damage.
I have fixed more overheated vehicles where I had to replace valves, rebuild/resurface the warped cylinder heads on them, and in some cases even re-ring and hone the bottom end than I can remember at this time. This isn't my first day. I know what happens to motors when they overheat. I've seen it. I've fixed many. Nothing happened to my car which even surprised me. I was only at 280 ish for a short while. When I popped the hood and noticed the fan was not spinning I got back on the open road to force air through the radiator and brought the temps back down quickly. I avoided driving in traffic until I fixed the fan problem.
The OP asked how how till the head gasket blows on these cars. I can't give an exact answer. What I can say is that I hit at least 280 degrees on the guage at least two times on the same day with mine and my head gasket didn't blow nor did my compression readings change or suffered any engine damage.
Last edited by 86PACER; Mar 17, 2011 at 11:39 PM.
Thread Starter
Racer
Joined: Jul 2007
Posts: 462
Likes: 21
From: Kansas City Missouri
In looking at how to proceed, given that I have antifreeze leaking into the oil.......if I have to yank off the heads again, do I have to get them machined? I was told that is a good idea, but they are brand new. The motor has only been ran for 12 minutes. Opinions?
Also, I have heard of new heads being warped. Apart from this, any thoughts on why a brand new set up would have leaked? We torqued everything to spec...used the right gaskets...etc.
Also, I have heard of new heads being warped. Apart from this, any thoughts on why a brand new set up would have leaked? We torqued everything to spec...used the right gaskets...etc.
Racer
Joined: Mar 2011
Posts: 296
Likes: 0
From: Derby (Wichita area) KS
If you have to go to the trouble of pulling the heads you should have them checked for flatness at a shop. Obviously something's wrong with the original repair for it to fail in 12 min, might be that the heads are just fine as they were machined prior to reassembly right? In that case maybe some other reason the gasket did not hold, possibly debris or maybe incorrrect installation or torque sequence...etc.
Race Director
Joined: Jul 2000
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From: Out Where the Buses Don't Run, Eglin AFB/ Niceville FL
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The electric fans quit on my 89 once in traffic. I hit 263* before I could breakaway and get air flow. I drove another 2 miles home. Aluminum heads and no damage. It scared the crap out of me when the red warning light lit up. I would not recommend over 245* and only briefly. I hit that few times in traffic in Phoenix in the summer.
