Engine Problem!!! Mk1, 1989 help!!!

[mikeym]

Hey guys,

I just recently bought an toyota mr2 mk1... its a 1989... the engine had a loud knock when i bought it.... so for the past 3 weeks my dad and I have been working on it and just finished up yesterday...

(please bear with me i don't know very much about the whole process, but i'll try to explain the best i can)

we took off the oil pan and examined the rod bearings... the were shot on 3 of the 4 pistons... we also checked to see if the rods were bent, they were not....

my dad said he noticed the journal for one of the rods (for the bearing to fit on the camshaft) was pretty worn. he said it shouldn't have been a huge problem tho, it wasn't a really really tight fit but it wasn't totally sloppy either....

we put the engine back together and it sounded great! everything was running fine... so we moved on to the body and finished cutting out some rust, body puttying, sanding and spraying....

we took it out for a ride yesterday we went about 3 miles and then stopped to get gas... we noticed the engine was pretty hot.... and checked the radiator fluid, it was pretty low but there was some in there yet....

on the way back we noticed a knock developing.... as we got home my dad manually rev'd the engine from the back of the car and at high rpm's the knock is loud as hell.... but idling and giving it a little gas it sounds great....

he was thinking maybe the thermostat is gone bad or not kicking on and the cars not cooling itself.... could that cause a knock?!!?

it doesn't sound like the valves at all....

please help if you can.... i'd like to fix it with the least work required...

thanks guys!

~mike

[86AW11]

make sure you burp the coolant properly, mr2 or haynes manual for procedure. i like mobil1 15w50syn oil. change that thermo its cheap!

[mikeym]

^that has nothing to do with the engine knock at high rpm's tho... right?

but i'll make sure i do that properly....

thanks for replying, any idea what that knock is?

~mikeym

[4AGmk1toytech]

sounds to me like its more of the con-rod bearings..
really rare valves knock unless its bent and your engines an interference engine(which the 4AGE isnt)..it'll just make ur car run shitty..
also another possibility(worse case scenario) is head gasket shot..common on mk1s..happen to mine,twice actually..2nd time i just decided to rebuild the whole thing.
when i ripped the head apart..saw a nice blown out gap between cylinders 3 and 4 on the gasket..wut happens is when cyl. 3 is on its compression stroke..the air/fuel is compressed but leaks thru the gasket goin into cylinder 4 and then cylinder 4 goes into its comp. stroke(1,3,4,2 firing order)...in another words..cyl. 3 is "supercharging" cylinder 4 ..haha..and it detonates cyl. 4 like a mofo.

[ToyotaTechGeek]

another thing to remember is that when you just replace bearings w/o doing a re-build, you could still have shavings and what-not in the engine. so, this could cause problems down the road. you can also have bad wrist pins, or a blown ring land, or a couple of other things like stretched con rod bolts, etc.

[mikeym]

thanks guys...

i think because the journal on #4 was shot it just flattened the bearing out again...

thats my guess...

how long could the car run with 3 good pistons and a 4th with a shot bearing?

its gonna chew the hell outta the crank...

i'm hoping to drop in a new engine in awhile if i can save up enough money...

~mikeym