Please not another popped head gasket.........weird temp issues yesterday!


Authorized Seller
Aug 10, 2010
bloomingdale, illinois
summary... owned my sup for 14 years. i know the tell tale signs of popped head gasket.:icon_evil
just took my supra out of storage this summer after its been parked for almost 8 years, only driven occasionally in those 8 years (like 40 miles a summer)
, did a auto to 5 speed swap, clutch masters stage 4, fidanza wheel, arp bolts, rebuilt r154, c's short shifter, new precision 62/65 billet with turbonetics divided housing, sp racing quick spool valve, all new fabricated downpipe and custom mid pipe, aem wide band, new warlboro fuel pump, big end fuel psi reg with gauge, reflowed the RC engineering 550 injectors to be safe, car has JE pistons,ARP main/rod bolts, ARP head studs, metal headgasket. old/outdated hks piggyback vpc/gcc/fcon/fcd etc...
started tying up all loose ends on car that ive never addressed. floormats/front bumper lower trim, new speedo cable, new brakes, stainless lines, replaced rear metal brake line that runs from front to back.
car made 440 at the wheels at a modest 18 psi. car falling on its face on the big end with stock cams
been running 1/2 and 1/2. 100 octane/93 octane and cars been running great.

the weather has just turned cold here in chicago and my heat wasn't working. troubleshot it down to the heater control valve wasn't opening, so i temporarily hooked vac straight to it so i would have heat. i did this on fri. drove the car for approx. 20 miles with no problems.
yesterday i was driving into work on the hi way and did a pull in 3rd gear a little bit/nothing crazy. immediately after my temp gauge shot up.:nono:
chilled out/blasted heat/temp came down/ . i immediately looked in rear view when i noticed the temp spike expecting to see smoke but there was none.
got to shop let car cool, checked coolant and was super low. guessing almost 1/4 gallon?
absolutly no smoking so the car isnt burning it
now that heater control valve is open, that account for drastic coolant level change?
topped off coolant, drove car home (15) miles/hi way/open throttle at times, everything seemed fine.
parked car at home for 2 hours, and hopped back in for a ride, drove not even 1 mile and temp gauge almost pegged, pulled over shut off engine, popped hood, everything looked/smelled normal. WTF. let electric fans run for a bit, fired engine back up, temp gauge back to normal. drove for about 3 miles and parked it back at home.
same oem style radiator since ive owned the car since 1996
replaced water pump once since ive owned (guessing 50k on this pump)
just replaced thermostat to oem toyota

so...either I have alot of air in the system (possible,but ran up to temp with cap off yesterday when topping off)
faulty temp gauge/sending unit (unlikely)
bad water pump? (wishful thinking/possible)
radiator? (wishful thinking,but i guess very possible)
head gasket starting to go south? :: angry ::
inspected all hoses, replaced lower hose, and small hoses off back of thermo housing.

any ideas?

god i hate that feeling of desperation/jaw dropping when you watch your engine temp gauge sky rocket!

Devin LeBlanc

Apr 7, 2010
Las Vegas NV.
Sounds like air in the system.. When the gauge spikes and jumps fast that usually means its not in water, I would jack the car up in the front, turn the heater on and fill the coolant that way.. Did you cut the little valve out of the thermostat and make sure it points straight up? This will help a lot with burping the system..


Supramania Contributor
Authorized Seller
Dec 13, 2007
Abbotsford, BC
x2 on air in the system. Did you notice any waterfall sounds from the heater core?


is sofa king
Authorized Seller
Jan 17, 2006
Sedro Woolley, Washington, United States
I used to take a Pop bottle and trim it down, Take anti chafe tape and make a sealed funnel.That way the waterline is well above the Rad. I found that this keeps air from entering the system when the coolant drops. I have done this on at least five different motors in the last 6 months and never had a air problem.

I did notice that you have Electric fans. DO you have a shroud? With the age on them are they performing like new still? Loose connections? Maybe you could splice a light into the line to see if their is any current changes? Just throwing out ideas good luck and no wammies


New Member
Authorized Seller
Sep 12, 2008
Melbourne, Australia
Metal headgaskets do not "pop" Infact i'd be willing to bet you'll break the head first before the head gasket, I had one that didnt seal properly last about 9000km before i pulled it off, the gasket "looked fine" apart from the viton was eaten away.

Given you had new pistons installing it'd be safe to assume you got the block decked and head decked for the MLS headgasket, Is this correct?

As mentioned air in the system will cause this.


New Member
Authorized Seller
Oct 21, 2010
powell river bc
i agree with air in the system. remember to have the heater turned all the way up so it can fill aswell.

and those spill free funnels are the best!!