Bad Head Gasket?

[supradjza80]

Hi everybody,

Well it appears to me that it is now my turn to replace the 7mgte head gasket in my car. However the car acts pretty oddly so I figured I would throw this thread up just in case anybody had some ideas regarding it.

First off, I take my car out onto road racing tracks and this is the ONLY time that the cooling system has EVER acted up. My first event was at Road America on April 18th, where on the stock radiator I had a couple times where the coolant gauge spiked up to just below the red zone on the coolant gauge but would promptly drop (maybe a second or too later) down to the Normal zone. The car had filled the overflow but after cooling off all water went back into the radiator and the overflow was at normal height. Checked oil and it was all oil and still at the correct level, checked coolant and it was still all coolant, no oil floating on it.

I finished that track day and then drove the car approx 2k miles on the street to and from work, as well as doing many "fun" things on the street. The car never missed a beat, ran great, never mixed oil and coolant and Oil and coolant levels were consistent day to day. I pressure tested the coolant system and it tested normal, with the car not doing any of the BHG things I thought it would, I now started thinking my heat spikes were likely caused by my 17 year old radiator, so I purchased a Mishimoto replacement.

Fast forward to yesturday when I was out on Blackhawk farms raceway with the car. The car was filled with basically a 10-20% mix of coolant and de-ionized water (mostly water). During my first session, with the heater off the car never warmed up once, I thought "sweet problem fixed gtg". During my second session, it had got a little warmer out and since I did not want to worry about coolant temps going up I turned the heater on full blast during the session. On my 4th lap we were back to having momentary temp spikes on the gauge, but the gauge never sat at the redzone, just would spike up to 3/4 or 7/8 and drop down within a period of 1-3 seconds.

Came in at the end of the session and the car needed about .5 gallons of water (20 minute session). Talked to the people there with me, they said no smoke out the tail pipe, and I could see with the car sitting there that there was no white smoke coming out of it. Checked oil again, and it was again perfect. Needless to say I had this happen for another 2 sessions before I said ok enough I KNOW this isn't right and therefore do not want to risk it. On my final session when I came in the cooling system had no pressure (I could squeeze the upper hose no problem...I have a brand new 87-88 toyota cap on the mishimoto radiator). So therefore I know that there is some leak in the system blowing off pressure, I am guessing it is the head gasket. I thought it was most likely going to be cylinders 5/6 so I pulled the plugs but both plugs looked fantastic and do not have that nice steam cleaned look I would expect from a BHG.

Needless to say I let it cool down, checked the levels and drove it home. coolant system was perfectly fine on the highway home, and held levels perfectly just like it did during the 2000 miles preceding this track event.

Just in an effort to NOT pull the head needlessly I am wondering if anyone has any other ideas of what could be causing my track day headaches. The car is really fast out on the track, but not having consistent temps kind of ruins it

Other facts on the cars cooling system

OEM Thermostat - Replaced last Spring
Original water pump
Mishimoto radiator with stock shroud and fans
everything else is stock or OEM components

If you have read this far and have any useful comments regarding the need to either pull or not pull the head let me know.

Thanks,
Dave

 

[enjoyer]

Mine does the exact same thing. It's been almost a year now. Still can't find what's wrong....

 

[CyFi6]

Get a good water temperature gauge and stop using the stock gauge which is very inaccurate would be my first tip. Install the aftermarket gauge sensor in the water neck around where the stock sensor is.

When you talk about the pressure being gone after driving, it might be normal. Mine would do this. If you think about it, as the coolant gets hot it expands and pressure builds. Well after driving a lot, then coming down to an idle my coolant temps would rise to maybe around 200deg, then with it running i pop the hood open and that helps get rid of a lot of heat, within a minute or so temps dropped down to around 183, well with the temp dropping the coolant started to contract therefore all the pressure in the system went away.

During normal driving coolant temps fluctuate a lot more than you would think, and the stock gauge doesn't show it. Stock gauge shows you being completely warmed up before you ever hit 190, and shows you being overheated well after 210deg.

 

[arknotts]

Get a good water temperature gauge and stop using the stock gauge which is very inaccurate would be my first tip. Install the aftermarket gauge sensor in the water neck around where the stock sensor is.

When you talk about the pressure being gone after driving, it might be normal. Mine would do this. If you think about it, as the coolant gets hot it expands and pressure builds. Well after driving a lot, then coming down to an idle my coolant temps would rise to maybe around 200deg, then with it running i pop the hood open and that helps get rid of a lot of heat, within a minute or so temps dropped down to around 183, well with the temp dropping the coolant started to contract therefore all the pressure in the system went away.

During normal driving coolant temps fluctuate a lot more than you would think, and the stock gauge doesn't show it. Stock gauge shows you being completely warmed up before you ever hit 190, and shows you being overheated well after 210deg.

+1. I would get a better gauge so you know exactly what your coolant temperature is at. This way you can closely monitor the fluctuations. I have my sensor (temporarily) in the upper radiator hose. Therefore it will only read accurately once the thermostat opens, but because of this I know exactly when it does open (the temperature will rise very quickly up to ~180-190). Like CyFi6 said, the stock temperature gauge only tells you when you are close to overheating. My stock gauge reads fully warmed up way before the thermostat opens. Good luck.

 

[87M-GTE]

Dave

Are you on the stock headbolts? I can't recall.
My car did this for awhile, then it started pushing coolant out of the system.
If it starts doing that, I would say the HG went.

Also, considering that you do "enjoy" your car quite a bit, and it is on the stock HG, wouldn't be too far fetched.

You could do a leak down test on the car, much more accurate than a compression test.
It is esentially a boost leak test. You put pressurized air into the cyl and listen for leaks.

Here is a write up I copied for my own use. I am in no way responsible for this write up..

An engine leak down or "cylinder leakage" test is similar to an engine compression test in that it tells you how well your engine's cylinders are sealing. But instead of measuring pressure, it measures pressure loss.
A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. You can start with cylinder number one and follow the engine's firing order. Remember to put the piston at TDC before you test that cylinder.
To conduct the test, you need some sort of a "leak down tester". This is usually a threaded coupling attached to a leakage gauge. This tester is screwed into a spark plug hole and compressed air (80 to 90 psi) is then fed into the cylinder.
An engine in great condition should generally show only 5 to 10% leakage. An engine that's still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.
The neat thing about a leakage test (as opposed to a compression test) is that it's faster and easier to figure out where the pressure is going. If you hear air coming out of the exhaust side port, it indicates a leaky exhaust valve. Air coming out of the the intake side or throttle body would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn.
A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.
A cylinder that has poor compression, but minimal leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, worn valve stem seals, etc.
If all the cylinders have low compression, but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.
If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire or coil).

note:
All technical info is posted to offer you some "GENERAL" insight. So take it with a grain of salt. The information posted here is very BASIC. We will not be held liable for any of the information provided. We do our best to provide accurate, complete, and timely information. However, we cannot guarantee the quality, content, accuracy, or completeness of the information. You should always confirm information from another source to gain sufficient technical insight.

Hope this helps

Sam

 

[grimreaper]

The upper hopse should remain hard for a period of time after shut down. I noticed similar pressure lose and the rad. cap wouldnt hold more the 3-4 psi. Test the cap.

 

[levirolla]

Mine temp spiked for 2 years before mines blew. It would go up, then drop back to normal real quick. Turns out I had a coolant leak in the back off. When mines finally blew it spiked and air was getting in the system and started blowing smoke the next day.

 

[supradjza80]

Guys,

Thanks for all the responses, it seems cars with my symptoms were generally in the very early stages of blowing the Head Gasket. I did decide to pull the head after testing everything else in the cooling system. After verifying the correct operation of all components it was clear the water loss and loss of coolant pressure when the car is just coming off the track could only have been coming from the head gasket. When it came time to pull the head I was expecting some loose head bolts, but there were non. I was also expecting to see some damage to the firing rings but there was also no damage there. There were a couple areas away from the cylinder that didn't look perfect so I am guessing under the stress of the track I was forming a small leak and my cars symptoms confirm this.

Right before the head came off I did check compression, it was like usual 175 across every cylinder + - about 2 lbs. I have tested the compression 4 times on this motor and it has always been within just a few psi for all cylinders.

HOWEVER, after pulling the head I noticed that I had some scoring on my cylinder bores, in fact 5 and 6 had about 1" wide scoring perpendicular to the wrist pin location on the piston. The scoring is at least partially started in near the same locations (perpendicular to wrist pins and through the entire length of the bore) in each cylinder and it seems like it is on both the intake and exhaust side (which side is worse depends on cylinder). I can feel the scoring but my nail does not catch on it. I can verify that the cross hatching is gone in certain locations of the cylinder wall. Right now i am thinking its time to pull the block and freshen it up as well, however I am wondering what others think about it. Hard to believe what I am seeing considering the car has always had such great, even compression since I have owned it.

I will take some good macro pictures of the cylinders today and get them posted up in here. Any advice is appreciated, calling on IJ

 

[IJ.]

What was the ring end gaps set to Dave?

 

[supradjza80]

Stock? I really don't know, as far as I know I bought the car with 80k miles, head gasket replaced, bottom end never touched.

 

[IJ.]

Ahhh ok

will wait for the pics then

 

[supradjza80]

Better pictures are coming with photobucket. I just tried that attachment tool and don't like it too much.

 

[supradjza80]

Here we go, here is a link to more

http://s327.photobucket.com/albums/k463/supradjza80/

6 drivers side

5 passenger side

The rest

 

[CyFi6]

Can you feel any gouges/scratches?

 

[supradjza80]

Yes you can feel it, however your nail does not get caught on them.

 

[87M-GTE]

It doesn't look that bad.
Based on how well the car ran/the compression test conclusions I think it would be fine to clean the block up really good, mil the head go OEM HG with ARP studs.

What are your plans for the car? nothing too crazy right Dave? lol

Sam

 

[supradjza80]

Right, my plans are nothing to crazy for this car since I am looking at mk4's to ADD to the garage . But If people thought it was worth it to pull it right now and have the block and head done, I thought I would just do it. Waiting to hear what Mr. Grumpy has to say about it:naughty:

 

[IJ.]

Damn....

Come on guys "doesn't look that bad" WTF are you smoking... :nono:

Dave: My educated "guess" after trashing my 7M in much the same way is it's a combination of lean and high AIT that's ran the cylinder temps high enough to close a couple of the ring end gaps

 

[supradjza80]

hmm, my wideband has never shown anything above 11 under boost, and based on the fact that at least all cylinders are beginning similar wear marks it looks like they would all be suffering similar fates. Well I will pull ii out and see what we have. Based on the head gasket firing rings having no damage I thought it was unlikely that detonation was a cause.

IJ, do you recommend ring end gaps which are larger than the factory manual suggests? Wouldn't you expect low compression on the offending cylinders?

 

[IJ.]

I do the old school 4 thou per inch of bore top and 5 per inch 2nd and if I'm running the engine hard I add another 4 thou to the total and so far so good.

You appear to have caught it right at the start and it doesn't look too bad as far as closed gap damage goes so the comp figures would probably be okish, mine was a real hard pull to 8000 and when I pulled it down the Plug ground was gone and the ring was about half as wide as when it went in and the cylinder was trashed totally (brand new block)

Do you have any way to log AIT's?