Real time help - what are the 5 large plugs on the head's top?? (1 Viewer)

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IdahoDoug

IdahoDoug

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Aug 8, 2003
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I've found the leak, but I'm absolutely baffled. Remove the valve cover and you're looking at the twin cams on top of the head. Between the cams are 5 one inch diameter metal plugs with huge allen heads (female). My rearmost one is seeping. What are these and what's below them?

They appear to be there for machining purposes and are then plugged, but I don't know. They are between the cylinders if that helps - not above them - which is why there are 5 on a straight 6.

Anyone?

DougM
 
Doug, Could they plug water jackets in the head? Could be the water passages between the cylinders be specific to that given cylinder in the head? ie. water flows across the head not down the length? Don't know I've never seen the head off, just a thought.

BTW, how many hours in your HG replacement? I've considered as a PM
 
I can see them in the FSM cylinder head section, but no mention of what they are, nor are the pictures very detailed ~ just 5 circles shown between the valve guides. Are these what you're looking at?

I could sorta buy Andre's idea, but why would a horizontal coolant flow passage need five access ports so close together? That doesn't make a ton of sense to me, unless they really were just there to assist with the machining of the head. :confused:

When you took the head off for the gasket R/R, there wasn't anything on the block side of the head that would indicate a need for access of any kind, I'm guessing. It doesn't look like it from the picture.

You may just have to pull one and see what's underneath a la the hatch on LOST. Just make sure the numbers 4 8 15 16 23 42 aren't etched in the side of the head first.
 
They're called "plug, cylinder head" and there's a gasket sealing them. Cheap parts.

Doug, from your descriptions of coolant losses I think that you really ought to go ahead and re-remove the head and have it magnafluxed, measured, and generally made correct. Don't rely on a discovery of a minor topside seepage being the solution to your problem, much as you'd like to. The cylinder should have gone in the first time around and still needs to be brought to spec.

Consider: You yourself said that once the cams are removed you are within five minutes of removing the head when you "explained" why you weren't going to retorque the head. Don't the cams need to come away in order to change the plug?

edit to add: an overheated aluminum head will often leak from more than one place. Warpage can change every specification, change the shape of openings, alter the fit of attached parts.

(I know, you SAY that it's never been overheated)
 
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Doug, if indeed there is a gasket as honk says I'd replace it and button it up. I'm sure the head is fine and it's gasket is as well. From your description on how the engine is running I'd think it would have to be.

At this point he is nowhere near the 5 minute mark of removing that head. Still lots to go.
 
I diasagree honk, that all heads need to go in for pressure testing. While the pressure test would of cought this leak, or more testing before pulling the head would of caught this. Not all machine shops are set up to test this head. Unless the shop has done a coupe of these head they will not have the tools (specfic to the head)to test for pressure. The biggest mistake doug has made is not to measure the trueness of the heads surface when the head is off. He also has no loss of compression at this time, I do not think his head is warped. I beleive this is another of those little things that can creep up in the process of assemebly. Most of the 1fz head I have seen have not been warped and I tested for trueness in the shop with a true bar, look for visually sign of cracks between the valves. This is something I will have to check for inthe future, leaking cylinder head plugs.
This big nut is like the steel plugs on the side of the block, for the casting process to make the head. Instead of a steel freeze plug type thing, toyota went with a threaded part for better realiabity(and these are inside the engine). Well this one failed, some thing for all that has the head off to take a look at. As for retorqueing the head, all you really need is to pull the valve cover, remove the distributor, cam drive gear and remove the cams, no need to pull all the intake and exhaust stuff off. I personally would just repair this and see what happens. I think doug has found is source of the leak.
Doug, You did look every where else in the three oil drain to the block and the front timing cover area? If there is a seal there, I would also use some sort of mild lock tite or thread sealant of some sort to aide in the sealing of this. later robbie
 
Doug, in retrospec if you had discovered this first would you still have replaced the HG?
 
Morning all. Got a fast pressure oriented morning going on, but I think this is what the problem was from Day 1. At 12PSI it spits a drop every15 seconds. I'm going to fix this plug and button it up. I'm nowhere near head removal - did some creative removal to quickly get the valve cover off to run this coolant pressure test and it may have saved me a bunch of work. Had to find a creative way to block the open coolant lines, etc. I've got just 2 hours of disassembly into it.

DougM
 
90430-27005 is the part number for the gasket under the core plug, I would replace all of them while you are at it. List is $2.77 a rattle.
 
Doug

Just for fun, I ran some volume numbers. Assuming 60 drops per teaspoon (US standard apparently) your leak works out to about 2/3 of an ounce per hour at the 12 psi. That translates to about 24 hours of run time per pint - not a very big leak. Of course this all assumes my math is correct.

Tom
 
Dan,

Thanks - they're on order. Strange, huh??

Tom,

When the engine heats up, that leak may be faster or slower but I'm more intrigued by knowint that the US standard is 60 drops per teaspoon. I'll be tossing that one around in the kitchen tonight - heh. I'm having a heck of a time finding a hex to fit that plug. NAPA stops at 10mm for sockets, which is what I need - it's too deep down in for an allen wrench. Ditto Sears and every parts store I stopped at. A buddy of mine thinks he has one large enough. I think it's either a 14 or 17 - guessing. My 18 is too big, my 13 is too small....

DougM

DougM
 
Hexagonal bar stock?
 
IdahoDoug said:
Dan,

Thanks - they're on order. Strange, huh??

Tom,

When the engine heats up, that leak may be faster or slower but I'm more intrigued by knowint that the US standard is 60 drops per teaspoon. I'll be tossing that one around in the kitchen tonight - heh. I'm having a heck of a time finding a hex to fit that plug. NAPA stops at 10mm for sockets, which is what I need - it's too deep down in for an allen wrench. Ditto Sears and every parts store I stopped at. A buddy of mine thinks he has one large enough. I think it's either a 14 or 17 - guessing. My 18 is too big, my 13 is too small....

DougM

DougM
Click to expand...


what? you have no socket between 13mm and 18mm?
what kind of mechanic are you?
time for new tools! :)
 
Use a class 10.9 bolt nut combo, make sure the nut is locktite down with red. Just prep the surfaces with acetone for good adhersion. It's suggested that a cure time of 24 hours is needed for maximum strength.

Done right this will easily hold up to what you need.
 
Yea a simple 17mm bolt with a couple of nuts bound against each other on the other end or weld a nut on one end. then use a socket on the one end. If 17 is the size, could be done with a 16mm bolt head as well. quick trick. sorry about last night, I was in bed when you callled. later robbie
 
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