Sporadic Engine Overheating

[kmfdmk]

My Supra's down because it's disappearing radiator fluid. 350 miles to Baltimore and it ate 3+ gallons of coolant. Every 50 miles (or less) the temperature gauge would spike, and then drop back down. If I continued to drive it would begin to over heat and I'd pull over bleed off the pressure (steam) and add in another 1/2 to 2/3 gallon of fluid. Didn't matter if it was ICE WATER (the $16 dollar race coolant) or Prestone Red fluid ($12/gal) or Prestone heavy duty or 50/50 or water. It all disappeared the same w/ engine temperatures at the same.

My original suspicion was that once it's up to temp & pressure the fluid escapes via a pinhole under high pressure and then eventually presents a low coolant situation. At such time a bubble of air flows through the collant passages and that's when I get that first little bawble/spike in the temperature. A quick neutral-rev of the engine makes the temps drop back down. However from this point onwards continuing to run the engine will result in yo-yo'ing up/down fluctuations in engine temp till the engine will stay warm to hot.

Now I'm not really sure; my gut feeling tells me that the head gasket may have been incorrectly installed. But it's still developing pressure running great and not leaking a bit. The engine was run to Baltimore with thermostat in place and a new I believe 13lb radiator cap. However I've since removed the thermostat and it still does the same overheating problem. I'm not sure if I should go to the trouble of pressure checking the radiator & hoses, or just buy a new 6MGE from Aaron @ RabidChimp. I feel bad because I only drove the car for about 3 months after I got it back. And it was in the shop for about 4 months before that, and it's sat for the last 4 months.

Any suggestions on things to check, look out for etc? I think it'd be worth it to at least check the radiator, replace hoses and maybe flow check the radiator as well.

Previously my 85 supra developed a leaky head gasket and was leaking oil. It never had coolant and oil cross-mix, and never lost compression. Oil would simply leak from the back of the head when the engine was @ RPM's going down the interstate etc.

The following were replaced at the same time/along with the head gasket:


Front Main Seal[/*:m:8d17c]
Rear Main Seal[/*:m:8d17c]
Front Crank Seal (in the Timing Cover, behind crank pulley)[/*:m:8d17c]
Front Timing Cover[/*:m:8d17c]
Timing Belt[/*:m:8d17c]
Cam Tower Gaskets[/*:m:8d17c]
Valve Cover Gaskets[/*:m:8d17c]
Intake Manifold Gasket[/*:m:8d17c]
Exhaust Manifold Gasket[/*:m:8d17c]
New lifters (two were cracked)[/*:m:8d17c]
New Water Pump[/*:m:8d17c]
New Thermostat[/*:m:8d17c]

[daveb91]

I would check the spark plugs if you have a leaking HG sometimes it will leave coolant residue caked on the plugs. Also check the oil sometimes the coolant will go into the oil. Does the exhaust smell sweet when warmed up?

[Racerx300zx]

Any oddities with the viscous clutch on the raditor fan?
Def do a pressure check, have you had a chemical flush done on the whole cooling system?
Were there any odd noises right before it started acting up, possiblity of the w/p losing a couple impellers, I check with the garage and make sure they used a yota w/p, the advance special I got for the z last year went about 2 weeks and wheel and impellers on the w/p shattered, yummy cast iron wheel, oddly the nissan part came with a machined steel wheel and impeller.
I'd def check the fan clutch, it could be worn, the quick rev spins it back up, catches, and cools better for a while, till it gets to critical temp and then craps again, trying, but not succesfully cooling, thus allowing the coolant to overheat, pour out the overflow, boil and evaporate. Aside from that, no ideas

[kmfdmk]

The head was measured, & milled, 10/1000's were taken off, and it was pressure checked for problems.

Dave - No sweet smell on startup, or after running it hard. I would def. recognize this due to a radiator burn in my childhood. Will *ALWAYS* remember the smell. So far no cross-contamination since the engine work. Oil still looks clean; not milky, and the radiator fluid still looks normal (no oilyness/ oil slicks) I'll have to check for the coolant residue on the plugs next time I get out to where I've got it stored.

Liam - No problems with the fan clutch as the clutch has been eliminated using a direct drive 6 blade fan from Advance Auto Parts that sounds like a friggin' jet engine. Used an Advance Auto water pump I believe. Hmm.. now that I think about it it *could* be a potentially defective water pump. If the bearings were going out of it it would work fine till it got hot and the bearings swelled, then binding and having the fluid simply boil out the overflow onto the engine. AND with the massive amount of airflow created by the aftermarket fan it would rapidly evaporate. This is an easy fix, I'll get tags on it and get it pressure checked. If it passes the pressure check, I'll have it chemically flushed, and then replace the water pump.

At this point I'm trying to figure out if I would be further ahead to sell my 93 Mercury Cougar to get some money (I'm hoping to get around $2000 to $2500 out of it) and then use that money to fix the Supra.

I don't know if I should invest in repairs on the Supra's current engine since I just sunk $800 in parts and labor this time last year to get it running. It has 192,000mi stock internals AFAIK w/ new HG and all the new stuff I stated above. OR If I would be further ahead to get one of the 6M-GE's that Aaron has over @ RabidChimp.com (http://www.rabidchimp.com/mk2sup_rcp_6mge.htm) and drop that in since it's pretty much a direct replacement. I just want it running again...

Any thoughts? With a potential $2000 to $2500 MAX do you think it a waste to look into repairing the stock 5M-GE? I'm looking at the medium term. I potentially leave for Puerto Rico to work for a while (like possibly a coupla years. I'll be there for 6 weeks, and then have 10 days off, wash rinse repeat for the next 5 years)... SO I want to get it running ASAP. I'll make enough $$ I can come back and drop in a 7M-GTE or a 1JZ-GTE later and just PAY someone to get it done.

[Don juan futon]

Atleast pressurize the system and see if you can't find any potential leaks. Why not? If you don't find any, yet continue to lose coolant, then your gut feeling of the head gasket sounds like the next place to look into. It's either burning it or leaking it if you're losing that much.