'Diesel rattle' in my 350...?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

7900_Blazer

Full Access Member
Joined
Jun 15, 2021
Posts
151
Reaction score
104
Location
Texas
First Name
Francis
Truck Year
1975
Truck Model
Blazer
Engine Size
350
Not sure how to describe the 'rattle' I'm hearing coming from, I believe, the front of the engine at idle - not a consistent rattle. The rattle does not 'come and go'... but also is not consistent - so not something like rubbing as the engine turns....

Again, a bit of backstory... bought the truck from a guy in Denver - have replaced a ton of stuff getting it road-worth... the seller communicated it had a solid engine... with a torque cam upgrade.

After many months off work, I'm finally where I can drive it and the engine definitely has a 'rattle' in the front at idle. Kind of reminds me of a diesel rattle at idle, or maybe a really really bad water pump type rattle but the water pump spins freely and feels solid.

The truck has good oil pressure - 60+ when cold... never gets below 30 even when hot and at idle.

Thoughts?
 

Captcorvette

Full Access Member
Joined
May 2, 2021
Posts
192
Reaction score
498
Location
Dubai
First Name
Capt
Truck Year
1981
Truck Model
CK30
Engine Size
350
Does the truck have very old gasoline in it? Very low octane? When shutting the engine off does it die immediately or "diesel" a bit like it is trying to run then stop? Can you record the noise and send it in a file?
 

7900_Blazer

Full Access Member
Joined
Jun 15, 2021
Posts
151
Reaction score
104
Location
Texas
First Name
Francis
Truck Year
1975
Truck Model
Blazer
Engine Size
350
Does the truck have very old gasoline in it? Very low octane? When shutting the engine off does it die immediately or "diesel" a bit like it is trying to run then stop? Can you record the noise and send it in a file?

Thanks for your help.

Truck probably had some 'old' gas... but I put 10 gallons or so of premium in it the first time I was able to drive it a few miles as a test (4 days or so ago).

No, it doesn't 'diesel' when shutting off the engine.

Yes, I can grab a video this evening and post the link here.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,338
Reaction score
3,568
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
Fuel pump? Timing chain?? Is tgenoise constant, or will it come and go with engine speed? Take the belts off, is the noise still there? If so, it’s not a belt driven accessory.

Does the noise change shifting from park into gear? You said the noise appears to be coming from the front, a broken flywheel can make a funny rattling sound.
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,734
Reaction score
9,523
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
At idle...in gear? In park?
Does it change with engine rpm (ever) or no?

We're gonna need some pix of a 79 blazer pliz.
 

PrairieDrifter

Full Access Member
Joined
Dec 28, 2014
Posts
3,420
Reaction score
4,479
Location
North Dakota
First Name
Mason
Truck Year
84,79,77,70,48
Truck Model
Suburban k10, bonanza k10, c30 C&C, c10, gmc 1/2ton
Engine Size
350, 350, 350, 350, 350
Yup, front accessories or timing chain.
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,734
Reaction score
9,523
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Woah. What's the change between videos?
What belt? The water pump?

I thought "timing chain" at 0:04 and counted that sound 4 times before the first video ended. Faint at 07, 08, and 09. But that don't make no sense.
 

PrairieDrifter

Full Access Member
Joined
Dec 28, 2014
Posts
3,420
Reaction score
4,479
Location
North Dakota
First Name
Mason
Truck Year
84,79,77,70,48
Truck Model
Suburban k10, bonanza k10, c30 C&C, c10, gmc 1/2ton
Engine Size
350, 350, 350, 350, 350
Seems like water pump to me. Could also be the alt, spin those over by hand.
 

Snoots

Full Access Member
Joined
Jan 23, 2013
Posts
8,158
Reaction score
15,957
Location
Georgia
First Name
Roger
Truck Year
1973
Truck Model
Jimmy Sierra
Engine Size
350
Water pump.
 

Jawzjeep

Honk if parts fall off
Joined
Jun 5, 2021
Posts
442
Reaction score
819
Location
Washington
First Name
Joshua
Truck Year
1991
Truck Model
Suburban
Engine Size
350
If you haven't found it yet try putting a broom handle or a wood dowel against your ear then set the other end on the block in different places. CAREFULLY! It helps to narrow down the location.
 

78C10BigTen

Full Access Member
Joined
Apr 12, 2017
Posts
15,475
Reaction score
23,678
Location
pennsylvannia
First Name
Ted
Truck Year
1978
Truck Model
C10 BIG TEN
Engine Size
350
Well what i see only leaves 2 choices.... water pump or alternator. Only 2 things not turning after belt was removed...
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,698
Reaction score
11,148
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
If you haven't found it yet try putting a broom handle or a wood dowel against your ear then set the other end on the block in different places. CAREFULLY! It helps to narrow down the location.
Yes you can also use a rubber hose, which will transmit the sound just fine, but won't get thrown at you if you hit something moving. Still need to be careful. Also I think it's likely to be the water pump as well.
 

Jawzjeep

Honk if parts fall off
Joined
Jun 5, 2021
Posts
442
Reaction score
819
Location
Washington
First Name
Joshua
Truck Year
1991
Truck Model
Suburban
Engine Size
350
Yes you can also use a rubber hose, which will transmit the sound just fine, but won't get thrown at you if you hit something moving. Still need to be careful. Also I think it's likely to be the water pump as well.

Yeah your right. Over been beat by a rubber hose though? Either way its hurts to not be careful.
 

Latest posts

Forum statistics

Threads
41,847
Posts
903,385
Members
33,362
Latest member
Dhatch84
Top