Rb25det Belts Change

[GTSBoy]

Something coarse-ish. 180 is good.

[silviaz]

I just checked my belt, it wasn't super loose but I could bend it past 90 degrees a small amount so I tightened it up and for the first time ever my car didn't crank first time, had to crank it again lol. Don't know if that was because I tightened the belt or if it's my starter motor going out (been having slow starts for some time).

Coulda also been when I was recording I didn't crank the key properly and it didn't save the recording lol.

 

Is that a thing if you overtighten a belt it struggles to start?

Edited January 29 by silviaz

[GTSBoy]

1 hour ago, silviaz said:

or if it's my starter motor going out

This almost never happens these days.

1 hour ago, silviaz said:

Is that a thing if you overtighten a belt it struggles to start?

No.

Clean your battery terminals and make sure they are tight. Use sandpaper on a dowel if you have to, to get oxidation off the inside of the terminals, particularly on the -ve. Check the earth cable from battery post to chassis ground and engine ground. Make sure the contact surfaces are clean - including the threads on the bolts that anchor them - because that's where a lot of the contact occurs. Wire wheel on a drill is a good thing for this. Make sure the crimps on those cables are all sound.

Assuming none of that causes an improvement:

Check the battery voltage after it has been resting for a while. If it's at the lower end of the range, put it on charge for a while, then see if it will crank better.

[silviaz]

2 minutes ago, GTSBoy said:

This almost never happens these days.

No.

Clean your battery terminals and make sure they are tight. Use sandpaper on a dowel if you have to, to get oxidation off the inside of the terminals, particularly on the -ve. Check the earth cable from battery post to chassis ground and engine ground. Make sure the contact surfaces are clean - including the threads on the bolts that anchor them - because that's where a lot of the contact occurs. Wire wheel on a drill is a good thing for this. Make sure the crimps on those cables are all sound.

Assuming none of that causes an improvement:

Check the battery voltage after it has been resting for a while. If it's at the lower end of the range, put it on charge for a while, then see if it will crank better.

Will do. Suprised if it's not the starter motor considering it's 30 years old. Will get a volt meter though. Battery is close to new.

 

Cheers for your help, always appreciated.

[joshuaho96]

15 hours ago, GTSBoy said:

You can also get belt dressing in a spray can which can help to settle a belt in that otherwise wants to slip.

Everything I found online said never use it because it'll dramatically reduce belt lifespan. 

1 hour ago, silviaz said:

I just checked my belt, it wasn't super loose but I could bend it past 90 degrees a small amount so I tightened it up and for the first time ever my car didn't crank first time, had to crank it again lol. Don't know if that was because I tightened the belt or if it's my starter motor going out (been having slow starts for some time).

Coulda also been when I was recording I didn't crank the key properly and it didn't save the recording lol.

 

Is that a thing if you overtighten a belt it struggles to start?

No, but I have seen excessive v-belt tension cause the audible bearing noise from excessive radial load in things like alternators. So don't overdo it. Ideally you set it to manufacturer spec using a proper belt tension guage. I tried the "clicker" type gauges but those cheap things are trash. They read way too low even when you're careful.

[silviaz]

11 minutes ago, joshuaho96 said:

Everything I found online said never use it because it'll dramatically reduce belt lifespan. 

No, but I have seen excessive v-belt tension cause the audible bearing noise from excessive radial load in things like alternators. So don't overdo it. Ideally you set it to manufacturer spec using a proper belt tension guage. I tried the "clicker" type gauges but those cheap things are trash. They read way too low even when you're careful.

Funny thing is when i flexed the belt it seemed like it had the same tension as before. Like I didn't tighten anything lol. Will start the car again tommorow and see what happens

[GTSBoy]

12 minutes ago, joshuaho96 said:

Everything I found online said never use it because it'll dramatically reduce belt lifespan.

It's certainly not the first choice, but it is a perfectly good bandaid when the alternative is to anger f**k the thing with a blowtorch.

13 minutes ago, joshuaho96 said:

I have seen excessive v-belt tension cause the audible bearing noise from excessive radial load in things like alternators

It's not just noise. It f**ks bearings.

[silviaz]

23 minutes ago, GTSBoy said:

It's certainly not the first choice, but it is a perfectly good bandaid when the alternative is to anger f**k the thing with a blowtorch.

It's not just noise. It f**ks bearings.

I'm almost at a point where I feel like changing the alternator. Need to check the stuff you mentioned first though.

Edited January 30 by silviaz

[silviaz]

nvm this comment

Edited January 30 by silviaz

[joshuaho96]

1 hour ago, GTSBoy said:

It's certainly not the first choice, but it is a perfectly good bandaid when the alternative is to anger f**k the thing with a blowtorch.

It's not just noise. It f**ks bearings.

Yep, in my case as soon as I started hearing weird noises I backed off the tension until it sounded normal again. Delicate balance between enough tension to avoid that cold start slip and too much damaging things.

[silviaz]

On 1/30/2025 at 11:39 AM, GTSBoy said:

This almost never happens these days.

No.

Clean your battery terminals and make sure they are tight. Use sandpaper on a dowel if you have to, to get oxidation off the inside of the terminals, particularly on the -ve. Check the earth cable from battery post to chassis ground and engine ground. Make sure the contact surfaces are clean - including the threads on the bolts that anchor them - because that's where a lot of the contact occurs. Wire wheel on a drill is a good thing for this. Make sure the crimps on those cables are all sound.

Assuming none of that causes an improvement:

Check the battery voltage after it has been resting for a while. If it's at the lower end of the range, put it on charge for a while, then see if it will crank better.

I went to Repco to get them to test the battery using their tester (not a volt meter), alternator shows 14.3v when running, and when the car was off after the it was on full load I think it was 12.6v but the guy said it was all good. Terminals are all clean, no corrosion.

Though I coulda sworn when I tightened up my alternator belt the car idles a bit higher and the steering wheel shakes a bit until it's warmed up.

I wanted to confirm for the earth cable/s, are you referring to the 2 wires that are bolted onto the frame rail under the battery? I might be overthinking this a bit.

[GTSBoy]

19 minutes ago, silviaz said:

I wanted to confirm for the earth cable/s, are you referring to the 2 wires that are bolted onto the frame rail under the battery? I might be overthinking this a bit.

Yes. It's either "2 wires", or 1 wire, depending on how you look at it. It is the connection that ties the battery -ve to both the chassis and the engine. Every electron that goes in or out of the battery goes through those 2 small spots (on the inner guard and on the engine block). If those are not clean and tight, then shit starts to suffer.

22 minutes ago, silviaz said:

when the car was off after the it was on full load I think it was 12.6v

Yeah, but measure it again cold in the morning, after it has had hours to rest. You can't usefully test the charge state of a battery immediately after it has been running because the alternator puts a surface charge onto the plates that takes a while to soak in and balance out. It will always read higher, and potentially look properly healthy, when fresh off of charge. But hours later it can look a lot less healthy.

It's also worth measuring the battery voltage while cranking, although this can be difficult with a typical DMM because the screem update rate is so slow on most of them. An analogue voltmeter is actually a better tool for that.

If the voltage drops too far while cranking, it is a sign of a poor battery. Although I don't think we're necessarily looking for a weak battery here - just wanting to exclude it.

[silviaz]

6 minutes ago, GTSBoy said:

Yes. It's either "2 wires", or 1 wire, depending on how you look at it. It is the connection that ties the battery -ve to both the chassis and the engine. Every electron that goes in or out of the battery goes through those 2 small spots (on the inner guard and on the engine block). If those are not clean and tight, then shit starts to suffer.

Yeah, but measure it again cold in the morning, after it has had hours to rest. You can't usefully test the charge state of a battery immediately after it has been running because the alternator puts a surface charge onto the plates that takes a while to soak in and balance out. It will always read higher, and potentially look properly healthy, when fresh off of charge. But hours later it can look a lot less healthy.

It's also worth measuring the battery voltage while cranking, although this can be difficult with a typical DMM because the screem update rate is so slow on most of them. An analogue voltmeter is actually a better tool for that.

If the voltage drops too far while cranking, it is a sign of a poor battery. Although I don't think we're necessarily looking for a weak battery here - just wanting to exclude it.

Ah yep, will do. Cheers!