4a problem, maybe Broken/damaged valves???????

[maxhag]

hey guys,

I just thought i would get some opinons before i rip the engine apart or toss it out altogether..

My question is:

What would be the symptoms of broken/damaged valves in a 4A?



The story:
I was driving my 4a (in good cond, 280,000km, reg serviced) to work and i was just driving granny style (60kph) when suddenly lost engine power and it began to 'rattle' when i was to rev it. I pulled over..


After limping the car home, and inspecting the engine, this is what i have noticed.......

1. Only running on 2 cyl (cyl 1 and 2 NOT WORKING)
2. Spark to all plugs is ok
3. No engine rattle on idle or slow gradual revving BUT rattles when you give it a sudden rev.
4. Engine DOES NOT blow any smoke (fuel or oil) but exhaust smells very 'fumey'
5. Headgasket???? Water is perfect, no sludge etc..... Oil looks fine........
6. Idles smoothly (for only running on 2 cyl)

Any ideas?

I was thinking the valves but i havent delt with damaged ones before.............


thanks

J Riftin

[ke70dave]

prolly good idea to do a compression test before ripping it all appart, also check if theres any bubbles in radiator

also are you getting any blow-by out of the top of your crank cover, if your valves are buggered youll be getting alot of air out of there

[Gunner]

rocker assembly, most probably. pull your rocker cover off and have a look, a bent, stretched or brocken valve would do more then a rattle whil revving, i would think anyway.

pull the rocker cover off and have a look.

[slydar]

could also be broken crank. early 4ages do break crank shafts.

pairing of 1 and 2 kinda suggests this.

these engines have also been known to remain driveable with broken crank shafts.

sounds odd. sounds kinda bad though. luckily wrecker engines are not too expensive.

[slydar]

<div class='quotetop'>QUOTE (gunbz-r @ Dec 30 2007, 02:54 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=460502)</div>
rocker assembly, most probably. pull your rocker cover off and have a look, a bent, stretched or brocken valve would do more then a rattle whil revving, i would think anyway.

pull the rocker cover off and have a look.[/b]

there are no "rockers" in any 4age engines.

gunbz-r. you would be better off reading a little more and posting a little less.

[maxhag]

yeah, i did pull the cam cover off and checked springs etc...... all looks fine......

I was also thinking the same thing with the Crankshaft, but i thought it couldn't possibly run like that....


No bubbles in water...

[slide86]

comp test would be the best thing for this.

my daily had the same problem. turns out the head gasket blew between cyl 1 & 2. causing the compression to jump between cylinders . it was also only running on 3 & 4 cause of it.

i say comp test it and it should give you an indication as to whats going on in there

[maxhag]

will do this arvo....

I thought there would be other signs of the headgasket blowing ......

thanks guys.

Can someone also tell me the touque settings for the head when i put it back on....

Adios amigo's


J Riftin

[4A-GE Power]

If you had a broken or cracked valve the engine would still run but it definitely would not have dropped two cylinders completely unless a number of valves had gone. I'd say slide86 is on the right track with the headgasket. I believe 4AGE's do have a head gasket problem like 7M's do. Worse case the crank is gone but it would have had to be hammered for it to break coz they are pretty strong. torque specs as per Toyota 4age manual: torque all bolts to 22ft-lb in a criss cross pattern. then tighten a further 90 degrees and another 90 after that.

[maxhag]

its a 4a (SOHC) Not 4age. do they run the same cranks?

[4A-GE Power]

Oh woops. i just assumed you were talking bout a ge. You wouldn't think they run the same cranks. I know the main and big end journals are the same size

[Gunner]

so slyda ur tellin me on a 4ac, that the cam runs straight on top of valves? they have arms.

oh u said ge, i know they dont have arms, most twin cams dont.

[Gunner]

not being patronising or whatever, but how'd u test what cylinders are running? check and make sure all the shims are there, tho that'd make noise down low, but check it. and feel all the rockers for play.

u'd have to be unlucky to snap a crank, and i would imagin it would of made a fair bit of noise when it let go. i see it as a bit odd for a crank to sheer driving normally at 60ks, could happen but i dont see it as likely, if u were revin it hard or had it really loaded up yeh but cruisin at 60?

[maxhag]

If it is the headgasket, what is the 'Rattle' when throttle suddenly applied?????????

I can understand losing compression, but whats the noise?

[Gunner]

cause its not your headgasket, have u checked comp yet? pull the rocker gear out, go over it make sure nothings bent or worn, then look in all the cavaties in the head for any debree, check your valve springs, make sure they are all sitting square and are all the same height. maybe theres been a hotspot or a dry one, and a valve or two have grabbed in the head, and are stuck partionally open, theres your comp lose, and would explain a rattle sort of noise uptop, if the pistons are tappin the valve, then the noise is louder at the higher speed due to the higher frequincey it would make.

another thing, maybe the valve springs have sagged/gone soft, then at a highr rpm valves have come in contact with piston tops, which would kill comp, and cause the rockers not to sit right in the shim.(this one happened to my b6 single cam)

the latter is more likely, but somethins let go in your head

[maxhag]

Compression test results:

CYL
1 - 60
2 - 62
3 - 158
4 - 156

The head is now coming off....

[maxhag]

Just got the head off...... The headgaskt was rooted between 1 and 2 cyl........

[Gunner]

ah yeah thats good, still why was it rattling?

[maxhag]

Toymods boyz reckon the noise was 'detonation'........

[slide86]

<div class='quotetop'>QUOTE (Maxhag @ Jan 1 2008, 05:59 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=461423)</div>
Just got the head off...... The headgaskt was rooted between 1 and 2 cyl........[/b]


i am the king of the world

[slydar]

<div class='quotetop'>QUOTE (4A-GE Power @ Dec 30 2007, 03:43 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=460535)</div>
If you had a broken or cracked valve the engine would still run but it definitely would not have dropped two cylinders completely unless a number of valves had gone. I'd say slide86 is on the right track with the headgasket. I believe 4AGE's do have a head gasket problem like 7M's do. Worse case the crank is gone but it would have had to be hammered for it to break coz they are pretty strong. torque specs as per Toyota 4age manual: torque all bolts to 22ft-lb in a criss cross pattern. then tighten a further 90 degrees and another 90 after that.[/b]

all sorted now i guess.

but i would like to add re above quote -

4ag's dont really have a head gasket problem. never seen one with a blown head gasket first hand.

and cranks in big ports are known to break occasionally. you might guess thats why they made them stronger in the later engines.

that is my experiance anyway.

[maxhag]

How much does it usually cost to get a head machined?

[ToySprinta]

noramlly around $160 for a head service

[maxhag]

<div class='quotetop'>QUOTE (4A-GE Power @ Dec 30 2007, 04:43 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=460535)</div>
torque specs as per Toyota 4age manual: torque all bolts to 22ft-lb in a criss cross pattern. then tighten a further 90 degrees and another 90 after that.[/b]

i found this on the net. It has the torque specs for toyota engines. It IS DIFFERANT then what you have said...

http://aarc.epnet.com/application/8586/8586.htm

It says to do them up to 40-47 ft-lbs for BOTH the 4A-C and the 4AGE.........

any help?

[Gunner]

ah k, i suppose thats reasonable lol