ON Topic: 88 Supra overheating...

yes it is dude. the solution is classic bromothymol blue - starts blue, turns yellow if the gasket is failing.

[now you can reconsider paying $50 for a bottle of reagent that only really should be costing you a couple of bucks.]

works because the CO? in combustion product [about 15%] bubbles through the coolant, dissolves and forms carbonic acid, and reduces the pH.

"solutions of carbon dioxide in water"

two weeks, true. but having changed it sooner can mask the problem, particularly in early stages where gas leakage can be slight.

T-Stat?

If the head gasket is leaking and you value the engine AT ALL - DO NOT continue driving it. You WILL cause further damage. Ride your bicycle for a week - a head gasket replacement on even a 7MGE is only a good day's work for a decent do-it-yourselfer. Add a day for the machine shop to check (and possibly plane) the head and you should be able to do it over 3 days - working evenings.

Not the stuff I've used over the last 30 years. It was accurate even when the pH was way high.

OK - I checket out your reference - it is NOT checking the pH of the coolant. It is detecting CO2 by bubbling air from the cooling system through the reagent (which you have correctly identified) and if the air contains CO2 it is absorbed in the water the reagent is disolved in, forming carbonic acid, and changing the colour of the fluid.

From your reference- Bromothymol blue is mostly used in measuring substances that would have relatively low acidic or basic levels (near a neutral pH). It is often used in managing the pH of pools and fish tanks, and for measuring the presence of carbonic acid in a liquid.

A common demonstration of BTB's pH indicator properties involves exhaling through a tube into a neutral solution of BTB. As carbon dioxide is absorbed from the breath into the solution, forming carbonic acid, the solution changes color from green to yellow. Thus, BTB is commonly used in middle school science classes to demonstrate that the more that muscles are used, the greater the CO2 output.

From the instructios for the leak detector kit- To do the test, add the blue detector fluid to the (block-tester) plastic container according to the directions, and place it onto the radiator filler neck. The squeeze bulb is placed on top of the reservoir and squeezed repeatedly (Some block testers, have a tube that connects to a vacuum line instead of a squeeze bulb). Squeezing the bulb will draw air from the radiator through the test fluid. Block tester fluid is normally blue. Exhaust gases in the cooling system will change the color of the fluid to yellow, indicating a combustion leak. If the fluid remains blue, exhaust gases were not present during the test. The vehicle should be started and at operating temperature before performing the test. Vehicles with head gasket leaks may overheat, and purge hot water and steam out of the radiator. Perform this test, at your own risk, and do not do the test, unless you are experienced and are wearing clothing and equipment to protect you from burns, or injury.

Actually, that is the major cause of overheating that results in blown head-gaskets on Toyota M Series engines

But it didn't! I looked for tools, opened the hood. Looked for more tools, undid the bolts holding the shroud on the bottom. Found some tools, undid the hoses. Then had a coffee and a cig, undid some more bolts, looked for more tools, sprayed the bolts with penetrating oil, had another cig, undid the shroud, and of course, broke an ear off it removing it, yanked the old one, put in the new one, went grocery shopping, redid the hoses (after chanting "replace the bottom hose first" 50 times), filled it, had another cig and coffee and then had supper.

Going to get a t-stat and cap from Toyota Monday, and then test it out.

So I took it out of the garage, moved it to my work apron out back, had it running for about 7 minutes. Opened the bottle and took a good whiff...

What does it mean if it smells like exhaust...? :(

you can use it either way. if the system is bubbling, then the gasket is leaking. and don't need a reagent to tell you that!

otoh, if you use the reagent to test the coolant, and you can, then you have your result.

it's also used for testing radiator leaks at $50 per quart as opposed to $5.

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Nothing good.

That's what I thought you were going to say...

Not necessarily true. If you have air trapped in the system it will bubble like crazy as it warms up, and sometimes even blow all the antifreeze back out - without there being ANY leakage in the system

But if the PH of the coolant is "off" in the first place, the reagent will show you have a leak when you don't, using it your way.

Using it the right way, it won't lie.

Nothing stopping you (or me) from buying it for $5 instead of $50 and still using it the right way - to tetect CO2, not coolant pH.

It means PARK IT AND PULL THE HEAD.

ok, so i'm guilty of presuming that we're not talking novices here and that we know how to bleed a cooling system.

"off"??? not unless you've got a beer pump attached to your cooling system.

not true. early stage head gasket can persist for quite some time. one of my cars took roughly a year and ~30k miles between the overheating event that initiated failure and the exhaust venting into the coolant badly enough to be visible. and even then, it was only a small amount, and only when hot, not cold. all this would have been resolved with a pH test early on. if you're worried about a false positive, change the coolant, and re-test a couple of weeks later.

a decrease in coolant pH is /caused/ by CO?. i thought the cites were self explanatory. would you like more explanation?

And they don't know how to check for a damaged head gasket - RIGHT!!! Bleeding the cooling system requires different procedures on different cars. Some can be extremely difficult to "burp". Ever bleed the cooling system on a Renault R12???? And the Supra M engine is a BIT more difficult than some, although much simpler than many others. On some you need to remove a hose - and different hoses on different vehicles. Some need filling through the expansion bottle - all kinds of different ways -

We ARE talking to novices in this group

In many cases a 50% mixture of tap water and glycol is very high in pH

- and depending on the water source, it can be very low. Low PH (acid condition) causes corrosion in the cooling system. High pH (alkalinity) causes scale build-up in the cooling system. Correct buffering of the coolant prevents both problems - and ONLY a correctly buffered system can accurately be checked for leaks by testing the coolant with Bromothymol Blue. On the other hand, using it in a "sniff tester" as described to detect CO2 in the air coming off the top of the rad you can accurately determine if there is a combustion leak into the cooling system, regardless of the pH of the system before the test.

I'd be much more worried about a false negative - and leakage on a COLD engine is much more common than on a hot engine, when it is intermittent.Starting with a cold engine, with the sniffer tester connected and run untill warm under a light load (fast idle in drive on an automatic, or A/C on and headlights on high beam) will catch even a small elusive leak with fair reliability. And changing the antifreeze to resolve the uncertainty is totally un-necessary (even in your scenario), Antifreeze is routinely "reconditioned" by running ithrough a filter and the pH corrected by the addition of buffering agents. Antifreeze is a hazardous waste which must be properly disposed of - and it is also not inexpensive. Recycling the coolant is the responsible thing to do - as well as the economical thing to do.

When an engine warms up, the parts expand and the clearances decrease, causing many minor coolant leaks, both internal and external, to temporarily stop with the engine at operating temperatures.

That's what I thought you were going to say...

well /i'm/ not.

two things:

1. you shouldn't be filling the cooling system with tap water in the first place. it should be de-ionized/distilled. for precisely the contamination/corrosion reasons you cite.

1. who is supposed to be buffering these solutions in the first place? and for what conditions??? certainly not the end user. this is not a "one size fits all" situation.

yes in theory, but in practice, only in the later stages of gasket leakage. at which point, it's pretty danged obvious what's going on anyway.

i'm not. just change the coolant. it's a few bucks.

untrue. early stage leakage is usually only manifest when hot. we want to catch this thing as quickly as possible.

indeed, but later stages. in which case, bubbles in the coolant should be making the problem obvious anyway.

you can't recover ethylene glycol by filtering dude. sorry. and buffer with what? buffering with inorganics increases corrosion rates.

c'mon clare. it's $7 or $8 for a gallon. anyone not prepared to spend that on an accurate diagnosis needs more than their gaskets testing.

that might be something available to those working in large shops, but not the man on the street. besides, the "environmental hazard" is primarily to biosystems like dogs who like the sweet taste. while more so, its toxicity is not unlike that of alcohol. mmm.

not head gaskets - other way around. restricted linear expansion causes them to bow in the middle - hence warping. that's why it's usually the middle pistons where the leakage is evident. and if you can see bubbling when cold, the gasket is already pretty far gone. [maybe your experience is skewed - most shops only get to see late stage leakage since owners usually never notice early and thus never take their vehicles in.]

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Delay this fix and you'll get a nice crusty spot of corrosion on the block where the breach is. At that point, the new gasket may or may not hold; it's a crapshoot.

Boy, you two are just FULL of wonderful news!

The car has been sitting since Thursday. I have a very small garage so I'm looking to see if a friend of mine has a space I can use. How long can I wait before ripping it apart?

Once I get it apart, is there any suggested limit where I need to get it back together by? I understand "ASAP" is the best, but...

NEVER use de-ionized water in a cooling system. Distilled is great - and most tap water is acceptable. Virtually every dealership in the country uses tap water.

The garage when it is installed by a garage. I have never had the pH come out where it belongs with a 50% mix of antifreeze and ANY water. Many times it's been close, but USUALLY the pH is too high.

A false negative on many cars will cause engine damage before you realize you have a problem. ONE OUNCE of glycol in the crankcase of a Ford 3.8 can trash the bearings.

I've been a mechanic since 1969 - and I've seen more engines leak coolant only when cold than only when hot. The only reason you see it more when hot is because when hot the system is under pressure. Pressurize the cold system and generally it leaks more, and sooner, than when hot.

It is done ALL THE TIME. The coolant is filtered and a buffering agent is added to bring the pH back to spec.

Up here it's generally $14 per gallon. to the man on the street.

My experience may well be skewed a bit, because I've wrenched professionally for many years. (with many of those years on Toyotas) Many head gasket leaks have absolutely nothing to do with restricted linear expansion and bowing, and everything to do with gasket material failure, corrosion, head bolt torque, and many other causes. On the "M" engine, in particular, early head gasket failures were attributed to shearing of the gasket because of the large differential in expansion rates between the aluminum head and the cast head. Toyota got that problem pretty well sorted out by the time the 4M engine was introduced. Most of the 3M engines were also good - but the 2M (Early Crown ) engines had a significant head gasket problem. From 4M on up, the ONLY head gasket failures I ever saw were due to uverheating from blown hoses, leaky rads, and sticking aftermarker thermostats.

Our dealership saw just about every vehicle we serviced a minimum of twice a year - and the vast majority 3 or 4 times a year. We did not have many failures of any sort.