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
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
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: 13,144
Likes: 348
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.
