Weird knock from 7M

**Chivalry** · 22-08-2011, 05:17 PM

I'll just copy my post from toyotacressida.net as I didn't have much luck there. Will try to sort my alternator this week, but after a quick coast up the driveway to get the mail while the car was still cold, the knock is getting worse, but still goes away if electrical load is put on the motor (headlights, fan and rear defrost). It sounds like it's coming from the back of the block, and I know what that means

Any additional help/suggestions is very, very appreciated.

"G'day,

So a few days after I bought my Cressida, I noticed a slight knock from the motor at idle. Of course, the first thing I did was shit myself then had a shower and a cigarette. I was worrying that it could be a big end problem as I had seen numerous Cressidas in my search that had busted big end bearings. As I don't really have the money or appropriate tools to tear my motor apart at the moment, I kept it in my thoughts and hoped it would work out to be something minor. I noticed after 15-20 minutes of driving, even if the car had warmed up beforehand that the knock would dissipate at idle. I also noticed if you applied slight pressure on the accelerator at idle to pick it up 100-200rpm above idle speed the knock would become barely audible.

Anyway, after deciding it couldn't be a big end knock because it wasn't exactly a definitive sound and the car still drove well and had plenty of power, I thought about other possibilities. However, yesterday a mate came over and as we were leaving to go on a wrecking yard run for the day and the car was at the end of the driveway, I turned on the demist and fan as it was raining and windows were fogging up etc. Then as I turned on the headlights to pull out of the driveway, the knocking vanished completely at idle but the climate control panel lights went out - but the entire system was still working fine. When I turned the headlights/parkers off, the knock came back and the lights came back on on the climate control panel, I repeated this once or twice to make sure it wasn't a fluke. All my electrics work fine aside from my drivers seat being unable to go back and forth (still reclines and lumbar support still works), so my mate and I discussed this discovery a bit more.

Eventually we decided that my alternator could be stuffed, it seems to still charge the battery fine, but we couldn't think of anything else attached to the motor that would cause the knocking noise and be affected by auxiliary electrical load.

So could I be right in assuming that my alternator bushings could be shot, or could it be something else? I know I could always just borrow an alternator to see if the problem goes away, but that's more hassle then it is worth at the moment.

Any ideas?"

**madmont** · 23-08-2011, 11:10 AM

sounds like the harmonic balancer to me

**Chivalry** · 23-08-2011, 12:36 PM

I just checked the balancer, it does have play in it. Call me a mechanical noob but that isn't a good sign right?

**madmont** · 23-08-2011, 12:57 PM

not a good sign for the integrity of the balancer

**Chivalry** · 23-08-2011, 01:59 PM

Pick N Payless want $50 for 2nd hand ones, the lowest KM car they have (which I got my guard from) has 207,000KMs. Any idea what a good price for a new one would be? I found Toyota OEM ones for $556 but they are for 7MGTEs, apparently a different part number though.

Don't really want to spend over $500

**Cuzzo** · 23-08-2011, 02:08 PM

If you find a low km one at pick n payless wear large pocketed pants.

**Chivalry** · 23-08-2011, 02:18 PM

I thought mine had decent KM's with only 204,000KMs, but yeah I hear you man, the other one at PnP has 297,000KMs. Seems like the nicer ones are drying up now that all the P platers etc buy them. Any nice ones I saw while I was looking for mine are stupidly expensive. I'm still gutted I missed the champagne/mars bar Grande with less KM's then mine and in immaculate condition for only $3,000. My mate has an R31 Skyline, nothing special aside from the 500HP RB30/RB25 headed motor he built for it, he kept telling me to get a Skyline as he has excess parts (including turbos) to build another solid RB30 donk. He bought 3 of them a few years ago for maybe $4,500 all up. Now you're lucky to find good ones for good prices.

**thechuckster** · 23-08-2011, 02:50 PM

Find someone here with a BHD'd 7M, offer them coin for the balancer?

edit: fwiw, derekjay had a balancer for a 5MGE rebuilt recently, would suggest getting contact details of business name off him to get a price for doing yours,

**boxh34d** · 23-08-2011, 06:11 PM

Precision parts based in Wagga will do reco (and I think) replacement balancers for the 7M. From memory, it was around half the money of a genuine toyota one.

**CELICASUPRA7M** · 23-08-2011, 06:36 PM

Id be checking the keyway in the crank too when its appart.

**Chivalry** · 23-08-2011, 07:11 PM

Originally Posted by boxh34d

Precision parts based in Wagga will do reco (and I think) replacement balancers for the 7M. From memory, it was around half the money of a genuine toyota one.

8 months ago I could've just walked to Precision with balancer in hand and had it done, damn.

I'll see what I can work out this week and pass on anything I find out.

Cheers everyone, much help is much appreciated.

**88cameron88** · 23-08-2011, 07:36 PM

a knock coming from a 7m??.. that is not weird! lol
a bottom end knock in its early stages may be noticeable at idle and go away with some rpm as oil pressure rises. i have this issue with a 7m in a car that i have done 2 motors in. the motor still runs great, plenty of power, the owner takes it out at night and gets on the brake doing skids in the next street for 12 months now and the knock hasnt even developed.

i know its a bottom end knock because i fitted the bearings and i know for a fact that one is undersize.