head gasket replacement

[potatoe]

i have an '85 with a worn headgasket and was wondering what all i needed to do to replace it. halp plox.

[YellowJacket]

Take it to your local toyota dealership.

[potatoe]

thanks alot buddy. im not incompetent; i just moved from vws to an mr2 like 3 days ago.

[randomxzero]

Haynes Manual to know the pattern to take off/put on the camshafts and the pattern to take off/put on the head bolts...
Torque Wrench...
12 Point 10 mm Socket... for the head bolts and Tensioner...
10mm socket...
12mm socket...
14mm socket...
17mm socket...
small flathead screwdriver...

Head Gasket of course..
Camshaft Seals..
Valve cover Gaskets...

i just did mine in February and this is mainly what i used..

[potatoe]

thanks dude. im not used to head gaskets as bugs dont use em i wasnt sure if i would need to machine it flat for a nice seal or not. so its a straightforeward job then?

[randomxzero]

ya i forgot ha resurface head..
only took like 5 min to resurface and 20 bucks..
but other than that ya pretty straight job..
the book would make things so much easier
it tells you step by step you should get it...

[potatoe]

ok. i wasnt sure if i wanted to invest in another book because i have 3 vw books and most of the time im unsure of something the book doesnt say ****, but since i have less mr2 knowledge than vw i guess it couldnt hurt. thanks man

[tjmr2]

Read the BGB and thoroughly bleed the coolant at the radiator and heater before restarting the car. These engines are famous for over heating the head if air gets in the system and isn't properly bled out.

[potatoe]

yeah, i think i need to get on the head change pronto because its starting to smell really bad like its burning something and it feels hot, but the guage doesnt show it as being that hot.

[muffinman]

BGB
Free File Hosting Made Simple - MediaFire

[lsgheero]

bgb = big green bible lol i would dl that its the dealer service manual much more indepth then a hayne/chiltons could ever hope to be.

[boycelaforest]

I just took the head off my car yesterday. What a job.
Drain fluids.
Lift car, remove exhaust and exhaust manifold, remove intake manifold and piping, cam gears, valve cover, cams, take out headbolts.

[Jackstand Queen]

Unless you hear a loud blapping sound from the head, but not coming from the exhaust flange.

And unless there is oil contaminating your coolant

And unless there is coolant foaming up your oil

YOU DON'T NEED TO REPLACE YOUR HEAD GASKET.

[dirocyn]

Originally Posted by Jackstand Queen

Unless you hear a loud blapping sound from the head, but not coming from the exhaust flange.

And unless there is oil contaminating your coolant

And unless there is coolant foaming up your oil

YOU DON'T NEED TO REPLACE YOUR HEAD GASKET.

I don't know about that. But those are sure symptoms. I'd also consider a head gasket replacement if:

There is coolant loss but no leak under the car, and the exhaust smells sweet, or

There is low compression in two adjacent cylinders, or

you need to have the head off for any reason (valve repair, etc.)

[Jackstand Queen]

Thanks Dirocyn:

I'd forgotten about the sweet smelling exhaust, and missing coolant mystery hole. And I didn't think of the adjacent low pressure cylinders possibility.

Good thinking man.

[toyotaspeed90]

cylinders don't have to be adjacent... if one has low compression it can be leaking compression out the side, to an oil or coolant passage, etc.

You will need a deep 10mm as the cam bolts that hold the valve covers are long

you don't have to remove the intake manifold to get the head off, just make sure you get the support bracket unbolted.

you don't have to have it resurfaced if it isn't a problem.... have a very good and straight straightedge to check both the block and the head. When I have done HG's on toyota's in my own garage I have yet to find an A series that required a resurface.

[potatoe]

hmm. i get the coolant disapearing and an odd exhaust smell, i dunno about it being sweet though. and the other day it shot what smelled like oil out of the seal and onto the exhaust manifold. hadnt thought to check the compression for some reason.

[micker2]

Originally Posted by potatoe

yeah, i think i need to get on the head change pronto because its starting to smell really bad like its burning something and it feels hot, but the guage doesnt show it as being that hot.

Mine is doing something like this too, but I believe I have a coolant leak somewhere. When I top off the coolant before a drive, it's fine for several days. And then it starts leaking somewhere. The recirc tank gets full, but it doesn't recirc back into the coolant lines.

And, as potatoe mentioned, the gauge doesn't show it as being hot at all. Actually, now my gauge isn't working, but it started to get a bit hot a couple months ago and the gauge was at least moving but wasn't showing how hot it was. Where is the temp sensor for this thing? Is it the same one as the switch on the front of the radiator, or is that just to kick on the radiator fans?

Thanks much.

[YellowJacket]

Originally Posted by micker2

Actually, now my gauge isn't working....Where is the temp sensor for this thing?

temperature sensor gauge photo - aw11mr2 photos at pbase.com

[YellowJacket]

Originally Posted by Jackstand Queen

Unless you hear a loud blapping sound from the head, but not coming from the exhaust flange.

And unless there is oil contaminating your coolant

And unless there is coolant foaming up your oil

YOU DON'T NEED TO REPLACE YOUR HEAD GASKET.

Not true. While those can be tell-tale symptoms, they are only an indicator of specific scenarios of a BHG. They are not mandatory to diagnose a BHG as you indicate.
I have a BHG with none of those symptoms.

Also MR2 expert, RMeller, says

You can have a coolant leak in the exhaust side of your head gasket that is too small to find easily, that maybe just blows a small plume of steam when it is hot. When the car cools, the closed system goes to partial vacuum and takes in air at the leak which accumulates at a high spot, like the head. Then you get local boiling and the coolant blows.

Another MR2 Expert named Ron has this to say

I had the unfortunate luck on two engines. It was caused by a blown head gasket below cylinder #4. Coolant would leak out only after the engine got hot after running for an extended period to time. In my case it was about 40 minutes of freeway driving and less time if the temperature was above 80 degrees. The tear in the head gasket lead from the #4 cylinder to the outside of the engine, missing the oil passage. No coolant was detected mixed with the engine oil.

A small amount of coolant would weep out of the engine but would evaporate on the hot engine and there was never enough that it would drip on the ground. There was always a lingering, somewhat sweet smell of burnt coolant which I could not track down.

When the engine got hot enough, the hot gases would blow into the coolant passage and over-pressurize the cooling system. The hot pressurized gasses would eventually blow past the radiator cap and into the overflow bottle as steam. The steam would somewhat filled the bottle above the normal fluid level but the majority of the steam and suspended coolant would get discharged out of the cooltant bottle overflow tube. Initially it was hard for me to believe what was happening because I did not observe any wetness along the inner walls of the engine bay below the cooltant bottle overflow tube. I confirmed what was happening by making a paper towel tube and zip-tying it around the end of the overflow tube. The coolant was discharging out of the tube and some landed on the muffler which was also contributing to the burnt coolant smell. In both cases this situation only occurred while I was driving. It would not happen when I tried idling and reving the engine in my driveway or when I drove the car around the neighborhood at residential speeds.

It has happened to me twice on stock original engines. I have read of only one other incident so it could be very rare.

A long time ago, someone had a similar problem and it turned out to be a hairline crack in the cylinderhead to one of the coolant passages. When the engine got hot, the crack would widen and pressurize the cooling system. The crack did not leak coolant when the engine was cold and the compression tested within specs.

I forgot to mention that a board member reported that he had a leak in one the coolant hoses where it fits onto the radiator. Same type of situation. When the engine was operating at highway speeds it created enough pressure in the cooling system to blow coolant out pass the clamp. Before you diassemble the engine, check all the coolant hoses and fitting for leaks that may be heppening when the engine is operating at higher rpms. There is also a weep hole underneath the water pump shaft that starts to leak when the water pump bearing begins to fail.

In the second engine I took apart, I also found pieces of sealant the previous owner had used to seal the water pump clogging some of the smaller coolant passages in the head gaskets. The semi-crescent shapes with corresponding two small holes in the head gasket are passages for coolant to flow between the block and cylinder head. In one of the engines I was working on, I found pieces of sealant clogging these holes.