Cooling system gremlins!

[paradox616]

Hey,

im from Aus, i have a ma71 7mgte w/ w58 (targa)

Like all 7M owners i have an overheating problem.

first of all let me clear up a few things so i dont get "blown headgasket" responses

1) cometic MLS headgasket fitted
2) head machined, block wasnt, block was scraped of all gasket material
3) ARP headbolts fitted & torqued to 78ft/lb
4) new water pump fitted
5) new thermostat fitted
6) new radiator fitted (shroud for fan still exsists

my issue seems to be the temp rises to operating temp as per expected... however once at operating temp for longer than 5minutes or so the temp rises... ive bled the cooling system that many times, it appears the coolant system gets pressurised beyond normal operating spec, even with coolant this happens, ive checked and cannot find a single leak, and as far as i can tell there is no leak of coolant...

its as if there is a blockage in a water gallery causing the temp to build...


ive got a engine crane ready to pull my motor out and pull it apart but i thought id ask round see if anyone's experienced this, ive got a spare 7m but the guy who sold it to me rounded a headbolt (stock) so i cant remove the head... makes that block virtually useless

i suspected cracked head pressurizing the cooling system, or could my temp sender be shagged?

running the motor without the thermostat means it heats up slower but it still overheats.. im just stumped, any help would be great!

 

[IJ.]

Done a combustion gas test in the coolant yet?

As for the stripped bolt just drill the head with a 12.5mm bit so it pops off remove the head then undo the stud with vice grips.

 

[paradox616]

Done a combustion gas test in the coolant yet?

As for the stripped bolt just drill the head with a 12.5mm bit so it pops off remove the head then undo the stud with vice grips.

sounds like a sound idea, combustion gas test gets done by a radiator joint etc?

 

[IJ.]

You can buy a test kit and do it yourself, this will rule out a BHG as the suspect.

 

[grimreaper]

yes yes, dont do all that work if its not needed!

will it over heat at idle? highway? stop go? Does the overflow bottle over flow?

 

[paradox616]

well i took it for a hydro carbon test,

they confirmed that there is exhaust gasses in my coolant,

motor will come out shortly !

 

[IJ.]

Should be the very first test if a BHG is suspected

 

[paradox616]

yep!

how common is it to crack heads on 7m's?


should i

remove block, deck block & crack test, deck head & cracktest, fit new head gasket?


i bought a 7mge gasket kit from the states because finding them in Aus is like a fat man finding his penis.. and i couldn't find any GTE ones at the time

i used the intake gaskets because they were the same as the GTE,
the headgasket looks graphite, if my cosmetics infact damaged, would it be wise to use this or just get another one, im kinda thinking i should just fit a stock gasket for now if the cometics damaged, and if i blow it from just too much boost then ill do something about it?

 

[IJ.]

Not all that common to crack a head most times it's just bad prep work for the Mhg.

Yes you could use the composite HG but keep in mind it will still need careful preparation if you are going to bump the boost above stock.

 

[paradox616]

yeah, im planning 20psi in the future,

but 15psi for now, 20psi will involve a bigger turbo, i HOPE to push 14-15 through the ct26,

ive got a 600x300x80 fmic,

I will be getting the block checked and decked and the head decked and checked.. it should be obvious where the issue lies after i take it apart...

FYI i did a comp test on cyc6, 140 psi (10psi below what 8.5:1 is supposed to be) checked it 3 times, when i was removing the plug i heard the cooling system go GULP, as if i just released a vac seal


the motors already half way out, maybe a little work tomorrow and i should have it out of there!

i wish i was living in USA, 7m parts are sooooo cheap over there i bought a bunch of stuff when the aussie dollar was just about 1:1 bargin

 

[IJ.]

Where in AUS are you?

 

[paradox616]

Where in AUS are you?

The smokey city :1zhelp:

I'm from Melbourne East

 

[IJ.]

Northern burbs here

 

[grimreaper]

have the cam caps lapped and line bored while your at it, and the head hardness tested above all else first (usually IJ is all over this ).

good luck with it!

 

[paradox616]

well motors out already

i might tear it down tonight,

speaking to a machine shop.
im going to get the block decked, head checked, hone done, ill pick up a rebuild kit from the US and do new rings, pistons, bearings, timing belt.

does this kit look ok?
http://cgi.ebay.com/ebaymotors/TOYO...fTruckQ5fPartsQ5fAccessories#ebayphotohosting

ill probbly use a diff headgasket maybe another cometic if mines damaged.

would this kit be the same strength as stock spec? and if so how much power running a safe afr should it be good for?


here some pics

I know you cant see much but a machinest told me to check the clearance between the lifter shim and the cam at 0 lift, i did and there is a 0.25mm gap!!!! i pulled the cap off to check and there is no damage to the cap its self, inside the rocker covers looks clean as hell still

ill replace the cap with another i have from my spare motor and reuse my head... i assume it should be ok but ill get it checked out still,

BTW anyone know how to remove the valve springs in these heads?

 

[grimreaper]

you cant swap cam caps like that, they have to be machined for THAT head.

 

[paradox616]

you cant swap cam caps like that, they have to be machined for THAT head.

not swapping caps, head and cap look fine, a few small wear marks but no indication of damage but ive seen much worse,

i was talking about replacing the shim, as the shim in bouncing when the cam comes off lift

 

[paradox616]

ok well ive pulled the head off,

my cometic isnt damaged, i found no evidence of a bad blow out, or even where the water was leaking, i did find cyc 5&6 had a thin coat of oil (the rest were dry)

im going to reshim 2 valves aswell, i measure them all and 2 need reshimming...


i was also getting crossfire between cyclinders... intresting, ill post pics up soon...

EDIT: heres the pics