Blown Gasket or Bad Head?

[REadMenace]

I've been losing coolant in my 83 SR5 wagon, so I brought it to my Brother's shop for a check-up. He did a compression test which resulted in us discovering that pistons 2 & 4 are low and leaking into the cooling system. He's asked me to poll you guys and see what was more common -- blown gasket or cracked head.
This is my DD, I no longer have the luxury of walking to work, so getting a new head or replacing the gasket is pretty high priority.

Thanks for your feedback.

-Will

[dlb]

head gaskets are more common, judging from the many posts i've perused here. regardless of which it is, the head has to come off. if it is cracked, you should be able to see it upon close inspection.

did you overheat it before you noticed it losing coolant? a head gasket could go due to age but a head should not crack unless subjected to something extreme.

[Petros]

Welcome to the List!

Too bad about your T4wd, but cracked heads are pretty rare, I have never seen one. I have really badly overheated several toyotas, including a number of 3a engines. Never damaged a head, worst was I had to resurface it after a really bad overheat, but no cracks. That happened when the temp needle was pegged while I was carrying on a conversation and I was not watching the temp. The rad hose blew off, stupid me, do not try to save money by cutting off the bad end of a hose, they are that length for a reason! I must have drove it 4 or 5 miles with no water in it. The head need to be resurfaced. I have replaced 12 or 13 toyota head gaskets, most of them 3a engine, and never found a crack and only twice found it warped.

Have your mechanic use the procedure I have outline in the repair guides section (you might print it out for him). the service manual is written by a guy who never handled tools, and clearly did not know this car very well. My instruction will save time and money, and it will give you a few minor mods to make it more durable.

I recommend that if you get the head off, and find the head is still true (flat within spec), I would not bother resurfacing or crack checking, it is a good head. You would waste time and money checking for cracks on a Toyota head that did not even get hot enough to warp it. You could spray some dye check on it if you want to feel better, it does not cost much, but I would be perfectly confident in the head if it passed a visual inspection.

You might also need a valve job, that might be one of the source of low compression. It is pretty rare you have a head gasket fail in both number 2 and number 4 cylinder at the same time (one and two are the most common because they run a bit hotter). So inspect the exhaust valves (it is worth removing them to look at them when the head is off since there is some evidence they could be bad. If you do a valve job replace the exhaust valves, do not regrind them. the exhaust valves are not very thick and regrinding them will make them thinner and lead to valve failure (and possible very severe engine damage, I have seen it on many of these engines, including mine!). they do not cost much, so if you want the engine to last REPLACE the exhaust valves, do not regrind. the intakes can be reground no problem.

If there are no other problems with the head, the head gasket can be replaced in about 3.5-4 hours following my procedure. And you will only need a head gasket and a head pipe gasket (you leave the intake/exhaust manifold/carb, etc on the head). these only cost about $25 from Autozone or Napa. So do not wast your money buying a head gasket set, you get way more than you need. Even if it does need to be resurfaced and a valve job, I would just buy the head gasket, the intake/ex. manifold gasket, and the valve stem seals. IT saves you about half the money over buying a complete kit.

Only once did I find a water leak not caused by the head. And I have never seen it on another car of any type (I have been working on old cars for 38 years, including as full time mechanic for a number of years). That was where the wrist pin came loose in the piston, and drifted into the side wall of the cylinder and cut into the water jacket after many miles of rubbing on the cylinder wall. This is pretty rare for any car, especially a Toyota. I would not count on it, but there is a very small chance of something similar, or any number of odd-ball type failures that could cause water to leak into the combustion chamber. I would say you have an '85 percent chance it is only the head gasket, and only a bit higher it is anything more than a head gasket and warped head and or bad exhaust valve.

Good luck, let us know what you find.

[REadMenace]

I bought the car 2 years ago -- it wasnt firing in the #3 cylinder and was smoking heavily. When we tore the engine down, we discovered that #3 had critically failed, breaking into several pieces. We went through the long process of tearing the engine down and rebuilding it. We replaced the critical components and overbored the cylinders to correct the damage #3 had incurred at failure. When the engine was finally assembled we discovered that the head was warped, so we had it machined. For the last year and a half the Terc has been a reliable DD, I'm disappointed to have this issue so soon into it's new life.

We identified it as being the head or gasket as when cylinders 2 & 4 were at top-dead-center and pressurized air began to bubble out the radiator cap.

A final note, I realize that I have two accounts here by mistake. This one I created when I was an aspiring Terc owner, the other (WmSchaefer) I created after I purchased the Terc, as the password recovery system was not working. I'd love to straighten that out before I anger the Terc4wd gods.

-Will

[dlb]

petros has gone through a lot of head gasket troubles too. he has done extensive work on his 3A engine (overboring cylinders, flat top pistons, i can't remember what else) and it seems that 3A's don't like to be pushed. it's possible that something was overlooked when you rebuilt the engine but it's also possible that the overbored cylinders are too much for the rest of the components to handle. how much did you bore them out, do your remember? stock, they're 77.5 mm. 4A's are 81 mm.

were i in your shoes and had that engine history, i would consider putting in a new-to-you engine, and if you're going to do that then you may as well put in a 4A since it bolts in directly and has a nominal power increase.

[Petros]

-- it wasnt firing in the #3 cylinder and was smoking heavily. When we tore the engine down, we discovered that #3 had critically failed, breaking into several pieces.

what exactly does "critically failed" mean? the piston broke up? (I have seen that, too much piston slap from wear in the bore will cause the skirt to fail), or was the exhaust valve embedded into the piston top? Your head could be damaged whenever you have broken parts in the combustion chamber, the piston can push the loose pieces into the head and punch holes in it. I have seen that, but it is not really a crack, it is puncture damage. If it ran fine for a year and a half, I doubt that is your issue, but it is remotely possible that it would show up until now. A weakened internal wall thermal cycled and finally failed? It usually does not work that way, put it is remotely possible.

Again it is really odd that you have blown both the #2 and #4 cylinder head gasket. Far more common is to have one and two blown out between them, and into the water jacket.

If there is any question about the head you should just replaced it, you can get a used one from Picknpull for about $35 (you have to remove it yourself).

how far did you overbore it? There was a Technical Service Bulletin warning about boring .040" because of thin cylinder walls. I have overbored mine that far but I did not have any problems. The symptom is coolant leaking into the cylinders. If that is the case you have two options, sleeve the bore down, or replace the block. Complete short blocks are about $100 from PicknPull.

IT is too bad it is giving you so much trouble after a complete rebuild. I have rebuilt mine several times to sort out the changes I did. A hassle but now I have over 100k on the rebuild.

[toughtercel]

I had 2 crack block , (1) I had to replace motor two weeks after I bought the car , seller don't tell honest problem , (2) drove the car while coolant ran out , I replace the head and water still get into cylinder (junk it) . Like Petros mention ,it cheaper to find motor in scrape yard, If I were you , I look for "if there is " rusty,beater 80-86 Tercel for sale (cheap) and test drive it and let the motor idle for 20-30 min, then you know ,you have good engine to swap it instead of Auto Part Yard , You might buying crap motor from there too.It 50/50 chance .