[ThomasToTots]

Hey I got my new head gasket in the mail today. its from cnsautosports and I have had good luck with them in the past. but anyway I am looking at the new headgasket and there is something I do not understand. look at my head.

now look at my old head gasket

Se the build up on the gasket? my water jackets were clogged and now I think I know why. the jackets are long open spaces as you can see. the head gasket. old and new

both barely have little holes for the coolant passages. ALL the headgaskets for my car I find online (felt pro, barret something, etc) all match. and only have little holes. So tell me If you can mechanics. WHY? would would you want to block the flow of coolant in the block? look at the build up/blockage it caused

please tell why they make them this way. or where I can find one that doesn't thankyou -mike

 

[mcx]

i think it delays the coolant in the block so it can absorb the heat properly.

 

[ThomasToTots]

let me think about that for a moment. Im training to be a mechanic and we just went over cooling systems. coolant starts in the block (just a starting point) engine turns on and the thermostat is closed. the pump circulates the fluid in a closed system threw the block. threw the jackets and pipes. then when it reaches the proper temperature the thermostat opens and the coolant starts flowing threw the radiator as well. which helps lower the temperature of the coolant. ok thats basic. Im trying to rememeber my thermodynamics lessons. yes if the coolant stayed in the place longer it would absorb more heat . but its job is to cool the engine. wouldnt we want it to be effeciant and leave the temperature regulation to the thermostat? the confining of the jackets would increase pressure there. and I know the system is a pressureized system but other than making the water pump work harder and thereby robbing the engine of power why would the smaller hole improve proformance of the engine? (Im honestly asking because I dont understand)

 

[ThomasToTots]

ok thinking back to my heat exhanger lessons from the navy. the key to improving effectiveness of most heat exchangers is surface area. fins and baffles. more area that the coolant flows over the more heat it absorbs in a single pass. the jackets are wide above and before the gasket in order to maximize the cooling the coolant does as it flows. if the coolant is flowing too quickly it will not reach heat saturation point and it will not be that effective. if the holes are there to slow down the coolant to absorb more I guess I could see it. What is says to me though is that the system useing the crankshaft to dictate the speed of the pump is a crude but effective control system.

 

[marc780]

If i can make a guess, the dirty passages are maybe due to not changing the coolant often enough and not the restriction of the head gasket? If you are not sure if the head gasket hole sizes are correct then buy an OEM gasket from Toyota, or at least compare it to the one you have, and this might put your mind at ease.

You can be sure the toyota engineers designed the head gasket that way for a good reason, even if we're not sure what the reason is...maybe an email to Toyota about this issue would be a good idea.

 

[ThomasToTots]

I did compare it to all the ones I could find but I am going to go by toyota parts and ask to see one. Some people can take things on faith I desire to understand why. Its possible that it was ment to be this way for a reason. You are correct that not changing the coolant often enough will cause sediment to build up in the system blocking passages etc. But when you have such a small hole in such a crutial area of cooling I would imagine a blockage there would be catastrophic. and there was sediment in alot of the passages but if you look closely at the head pic. you will see the majority of my water jackets where caked in sediment that had built up at the gasket.

 

[white90dx]

The holes are designed specifically to route the coolant in the right places and speed. You want the correct flow of coolant around the cylinders to keep the whole motor at a constant temperature. Notice the larger holes are on the far end of the motor from the water pump?

Don't mess with success. I personally have owned one Camry that made it to 267k miles unopened (crashed) and another to 309k miles unopened (blown with a turbo by the previous owner).

-Charlie

EDIT: PS. You are going to need a new block!

 

[fredk]

it slows the coolant flow down to let the head heat eavenly

 

[ThomasToTots]

ok dont mess with the head gasket. Gonna need a new block huh?

 

[Skiermang]

My untrained eyes say those coolant passageways look really coked up in the block.

 

[ThomasToTots]

a view of the block after a light cleaning

 

[Doctor J]

Thanks for great pictures!
You have to clean it much better then that. DO NOT USE 3M SCRATCH PAD OR ABRASIVE BLOCK, JUST USE CHARCOAL LIGHTER FLUID, AND RAZOR SCRAPER (you may have to dull the corners of the blade.
Use new bolts for the head;
I would still use the OEM head gasket and aftermarket for the rest of stuff.
Leave the drain for the block open and flush the block after reassembly.
Put a stopper into the oil feed hole from block to the head (below the oil pressure switch on the head right next to the head bolt.
Get a tray to fit the head in, pour about 1/2 inch deep of odorless mineral spirit in there and dip the head into the tray. After 5 hours use wide blade scraper clean the head. Using straight edge, check the head for out of flatness (.002 inch any direction!!)
NEVER EVER USE the BELT SANDER to resurface head

 

[ThomasToTots]

thankyou. it was just a quick cleaning not preping the block for assembly. Shop called and head is ready for pickup

 

[fredk]

you really shouldnt mess with the carbon on the pistons because the pieces gets in between the piston and the wall and buggar things up, and the carbon around the edge helps the rings out to a degree

 

[Doctor J]

After receiving the head from the shop recheck it for flateness, especially near the ends

 

[ThomasToTots]

well fred I figure I am going to clean then anyway but ill keep that in mind. I got the ok from the wife. Im gonna yank the pistons and rebuilt the bottem half the engine. new oil pump, new rings new bearings.

 

[ThomasToTots]

well just an update. the new rings are on and the pistons are back in place, next is the oil pump. then its reasembly time. good times good times. post script. I plan on taking some good photos before the head goes on so you guys can see. Just out of curiosity, I took the pistons out 1 at a time, cleaned them, examined them, measured them, then ringed them and reinstalled them. so I know they are in the same order and position as when I took them out. why are my pistons inscribed with 3b ,2b,2c,3c? that might not be the order but they didnt count up and there was 2 bs and 2 cs. Its not fireing order . any ideas?

 

[Doctor J]

Those marks are the size groups.
On my 79 Supra the block was stamped near each cylinder.
Yours excellent photos + good write-up could make terrific repair process manual (that's what I am doing now after completing my degree)