Radiator Knocking Problem
Thread Starter
|
Senior User
Joined: Aug 2006
Posts: 255
Likes: 0
From: Pendergrass, GA
Radiator Knocking Problem
After my truck heats up you can hear a knocking coming from the radiator, I imagine they are air bubbles moving around.
Does anyone know what I can do to fix this? I am thinking it might be a problem caused by the thermostat. Was gonna replace it later today.
I have a 351M in a '78
Does anyone know what I can do to fix this? I am thinking it might be a problem caused by the thermostat. Was gonna replace it later today.
I have a 351M in a '78
Cargo Master
Joined: Oct 2010
Posts: 3,417
Likes: 32
Sounds like its time for you to flush the block. I drain the coolant when its still warm. Fill it up with a gallon or two of vinegar the rest with water and run her till shes hot. I.E. basically to get the thermostat to open. Then let the truck sit over night. Flush her out good in the morning. Next I take the radiator out lay it on its front with the cap on and put about 2 gallons of vinegar in it. You will have to top it off with water and let it sit over night. This will dissolve most of the deposits in the radiator. Put it all back toghether flush with water again. Then I fill her up with distilled water and antifreeze mix. I'd bet that you have deposits in the water jacket and radiator that are trapping air.
Thread Starter
|
Senior User
Joined: Aug 2006
Posts: 255
Likes: 0
From: Pendergrass, GA
Yeah. It was a little low and I filled it up, and it just blew out what I filled up. It needs a reservoir to solve that.
Thread Starter
|
Senior User
Joined: Aug 2006
Posts: 255
Likes: 0
From: Pendergrass, GA
Sounds like its time for you to flush the block. I drain the coolant when its still warm. Fill it up with a gallon or two of vinegar the rest with water and run her till shes hot. I.E. basically to get the thermostat to open. Then let the truck sit over night. Flush her out good in the morning. Next I take the radiator out lay it on its front with the cap on and put about 2 gallons of vinegar in it. You will have to top it off with water and let it sit over night. This will dissolve most of the deposits in the radiator. Put it all back toghether flush with water again. Then I fill her up with distilled water and antifreeze mix. I'd bet that you have deposits in the water jacket and radiator that are trapping air.
Trending Topics
Thread Starter
|
Senior User
Joined: Aug 2006
Posts: 255
Likes: 0
From: Pendergrass, GA
It's the radiator. It continues to do it even after I shut off the engine. LOL
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Senior User
Joined: Jun 2005
Posts: 321
Likes: 0
From: Atlanta
Are you sure you don't have a head gasket leak pumping air into the system? When I first rebuilt my motor I had one and it would bubble and burp pretty substantially running the motor and after I turned it off.
Thread Starter
|
Senior User
Joined: Aug 2006
Posts: 255
Likes: 0
From: Pendergrass, GA
I replaced the lower radiator hose with a flex hose that has a spring in it and I now have much cooler temps, but still have the knock. So I put 2 gallons of vinegar in it yesterday and drove it a few miles and gonna drain it this morning. Hopefully that will solve it.
Hotshot
Joined: Jan 2011
Posts: 13,120
Likes: 345
From: THIS IS SPARTA!, ...Mo.
The only time I've heard a radiator knock was when the engine over heated. Then there's a distinct and loud "knock" that sounds like metal breaking. Are you sure your temp. gauge is accurate? Is your water pump pumping? I'd look to see if your engine is really running hot or not. Flushing the system may help with cooling, which in turn will help the knock. Good luck.
