random knock

[sluttychunks1]

my car has a random knock. its not constant! it doesnt make any knocking noises at idle. it happens when i rev it up a little. while i rev it up it only knocks at a certain rpm range. it started last week when i left for work. i work 15 miles away from my home. when i was about a mile away from work i turned off the highway and my car died. the stock temp gauge showed it was about 3/4 on the temp gauge. i let it coast to a parking lot. i could notice some smoke from my hood so i popped it. there was alot of smoke. i could hear my coolant boiling. no leaks of any kind. there was plenty of coolant in it before i left to work. the only thing i checked so far was my compression. it was 180, 175, 175, 180. what else could this be? its not a constant knock. its not the turbo as i just replaced it about 1000 miles ago. any help would be much appreciated.

 

[jking29]

Does the knock happen at the same speed as the engine is running or does it sound faster than the engine?

 

[93_tsi_fwd]

Does it sound exactly like this? The video inside this link.

http://www.dsmtuners.com/forums/showthread.php?t=264989

 

[sluttychunks1]

it kind of sounds like that yes. its kind of hard to hear. ill try to get a video of my car... im going to try to add a little oil seeing as its a little low. my oil inlet line does leak a small amount. so i do keep a close eye on the level. i do have a problem with coolant evaporating. i did not mix my coolant with any water at all. the knock does not go with the motor. its only in a certain rpm range. im going to check it out tonight. just got done working and i may change my oil if necessary. the noise sounds like theres a loose piece of metal just knocking around. it is loud but again its only in a certain rpm range. ill check things over and get back on a little later.

 

[itzadawdge]

where is the knock coming from like wht side of the motor???

 

[sluttychunks1]

it kind of sounds like its coming from the head. i have an extra motor i started rebuilding. just going to finish rebuilding the motor and than rip this one apart and rebuilt it. going to start this weekend when i dont have to work. im thinking its either a spun bearing or a bent valve. pulling the oil pan tomorrow before work to look.

 

[300hpGS-T]

check the bolts on your water pump pulley, mine came loose once and started making a wierd knocking noise like nuts bouncing around in the valve cover (thats the best description i can come up with.) and it kinda makes sence seeing that your car overheated.

 

[sluttychunks1]

well coolant is just randomly missing too. i had to put coolant in 3 times within 2 days. my engine is full of some oil and grime. i bought it with a blown head gasket. and i noticed the other day my water pump is super clean.. i really dont got much time during the week to work on it. TGIF. im going to check out some more things tonight. what would be the cause of my coolant boiling? thermo or pump right?

 

[sluttychunks1]

i have noticed a few bolts coming loose too. they just start to fall off. a nut off the downpipe, the lower bolt on the alternator. theres a few more too. this car has been nothing but problems for me. fix one thing 3 more go wrong. joys of a dsm.

 

[sluttychunks1]

Problem is 2 spun rod bearings. Cylinder 1 and 4. Cylinder one looks like it just started spinning and 4 is kinda nasty. The cause? My t25 that blew awhile back. When i dropped the oil pan i noticed a bronze tint to some of the oil. I drained the rest of the oil out of the pan and found a bunch of metal chunks and shavings. 3 pieces of t25 bearins, some retaining clips that broke, and some metal from rod bearing # 4. cylinder 4 on the crank is not too good. It started to make rins in the crank. im going to file it down with some emery cloth and put in some new rod bearings and see how she is while i finish building my spare motor. Thank you for your help and advice to all.