I'm new to this forum, so hello everyone! Thanks to the internet I found you guys. The shop I normally use won't check/pressureize the cooling system for fear of blowing the headgasket, if that's what it is. The shop is a tune-up shop basically. Is there a way to tell for sure it is the headgasket without pressurizing anything?

Problem first appeared as I pulled into parking lot at work. Engine was clacking really loud and I discovered it was about 3/4 gallons low of coolant even though the temp guage never reached half way to the red mark. Topped it off with coolant drove home 15 miles, still clacking and was about 1/4 gallon low. Next morning drove 15 miles to the shop and the motor was running really quite/normal. Clacking returns when coolant level gets low/below ad in the overflow reservoir...Clacking disappears when filled with coolant. Meanwhile I've noticed that my temp guage stays much cooler with my heater off and runs hotter with it on. I don't see any coolant leaks even though the timing cover and waterpump area looks like I've got an oil leak. My timingchain was replaced about a year ago.

Engine has 166,000 miles. I'm beginning to think it may be more feasable to get a remanufacture engine put in if it really is the headgasket. I can't do the work myself and the price of labor will kill me.

Notice experience dictates that I jump directly onto the worse case senerio! Any suggestion is greatly appreciated!

Hey, welcome to the board.

I'm chasing a coolant leak, also. Problem with leaks near the block is that they evaporate rather quickly. One thing a co-worker suggested is that you can put a dye in the coolant which will leave a trace where it leaks. You can then view it w/ an ultraviolet light (black light). I just picked some last night, like $4 at Napa. Heard it works well, you may need to do it in the dark to see it better, from what I hear.

Might help....

A couple of things you can check out easy enough for yourself if you want to. First pull the plugs and check them for any build up or moisture if it has been sitting a while that would indicate coolant leaking into your cyl.
Leave it run in your driveway for a while and see if you can locate any leaks, place a sheet or piece of cardboard under it when it's parked to help in your search.
You may need to vent your system also, I wouldn't expect it to be making clanking noise if the overflow was not completly empty (I may be wrong on this one). Make sure you park it on a slight upward angle and run your heater while you vent.
The temp. difference when running and not running your heater was mentioned before, something to do with the heater return dumping close to the thermostat and it's cooler form going thru the heater core, therfore keeps your thermostat closed longer so engine runs hotter.

Sorry this is sooooo loooong, hope it helps.

HAve the shop hook up the pressure gauge to the radiator and see if the engine itself it pressurzing the system. That is watch for the pressure to rise due to the engine compression leaking into the cooling system, if indeed that is the problem. Another way to check that is a chemical test of the coolant checking for exhaust gas contamination:
- http://www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm

And running hot with the heater on is a common 22RE (I assume) problem with a fix from Toyota:
- http://www.4crawler.com/4x4/CheapTricks/index.shtml#Thermostat

Thanks for the suggestions. I'm going to get some of that uv dye stuff from NAPA this afternoon and I'll check my sparkplugs this weekend.

One thing I remembered was when I first started the engine yesterday morning...still cold...I loosened the radiator cap, but put it right back on because coolant was being forced out. Not extreme pressure, but enough so I didn't want that much coolant spilling on my carport floor. Should it force coolant out like that when it's cold, or could air trapped in the system cause it?

Normally it is the heat of the water in the cooling system that builds up pressure. When you hit 212F (at sea level) you get 14.7psi which just equals atmospheric pressure and plain water would boil. When the water cools the pressure falls. If there is pressure remaining when cold, that means something added pressure to the system and that there is some trapped air or gas in the system holding that pressure.

I had a HG leak in an old VW diesel engine and before I knew it was there, I would always hear a hissing sound when I shut it off and there was always pressure in the cooling system. Since it always did that (bought it used) I thought that was a normal "diesel thing". But as it turned out, a cooling passage in the head had eroded out so that it was too close to the cylinder opening in the HG and a small leak developed there. Would only allow engine compression into the cooling system but not allow the pressure in the cooling system to leak back out. Under heavy engine loads, the cooling system would overpressurize and the rad cap would blow, venting a pint or two of coolant in the process in the form of steam (only would happen while driving). Temps would remain normal until such time as the coolant level had dropped sufficiently to cause overheating.

That's probably where my coolant is going...out the reservoir's overflow tube and onto the highway. One check for the waterpump in this book I have was to get it to operating temp and squeeze the top radiator hose and feel for a swoosh when you release it. The top hose on mine is so pressurized you can't squeeze it together. If the headgasket is blown would the pressure be constant, or a pulse as the piston operates up and down? I pressure I feel is constants. Maybe I didn't squeeze it hard enough, but I'd really have to bear down to pinch it all the way together. The lady I work with's boyfriend has a shop and Monday is going to check it out with some of the stuff that turns yellow when exhaust gasses are in the coolant. If so he's going to replace the head gasket.

What I have seen is that the HG leak is often like a 1-way check valve. Lets the gas under several hundred PSI cylinder pressure into the cooling system, but not the 15 psi liquid coolant into the engine. Of course, over time, the size of the leak increases to the point coolant can dump into the cylinder.