The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 08-26-2002, 05:00 PM   #1
Bob Hinz
Registered User
 
Join Date: Aug 2002
Location: Maine
Posts: 6
Exshaust Gases in coolant system.

Have a 454 engine that seems to be building up a lot of pressure in the coolant system. took the heads off and had them checked and still have that same problem. Doesn't appear to be over heating as far as I can tell. Put on a new Termostat, water pump, hoses just for GP's. I was told that the block was bad and I was getting exshaust gases in the coolant system, but I have a hard time with that. The oil is clean and when I had the heads off, there was no evidence of coolant getting in to the oil. Using a 13 psi Radiator cap, maybe need a larger one? Help!!
__________________
Bob Hinz
Bob Hinz is offline   Reply With Quote
Old 08-26-2002, 05:10 PM   #2
jku72
Registered User
 
Join Date: Jan 2002
Location: cornville, maine
Posts: 659
If cracked, it is quite possible to get exhaust gasses into the water, but not have water in the oil. If the crack is small enough, a firing pressure of 500psi is a lot higher than 13 psi in the water system. The 13 psi may not be strong enough to force water through the crack(if there is one) but the 500psi is certainly strong enough to push air into the water. These can be hard to find.
But, hot spots can cause local boiling and overpressure as well, boiling it over. Anyone who ever owned a pontiac can verify this.
Check everything first, but there could be a crack.
jku72 is offline   Reply With Quote
Old 08-26-2002, 05:14 PM   #3
Bob Hinz
Registered User
 
Join Date: Aug 2002
Location: Maine
Posts: 6
What's causes hot spots and local boiling?
__________________
Bob Hinz
Bob Hinz is offline   Reply With Quote
Old 08-26-2002, 05:16 PM   #4
ChevLoRay
Old Skool Club
 
ChevLoRay's Avatar
 
Join Date: Jun 2001
Location: Benton, AR "The Heart of Arkansas"
Posts: 10,880
There are smarter people on here than me, but here is my 2-cents worth.

Get one of those cooling system pressure testers like the shops and stations use. Put it on your radiator, as if you were going to check the cooling system for leaks. Heck, go ahead and pressurize it before you do the following. After you have pressure-checked the cooling system, and you've tightened all of the loose hose clamps, fire it up. Leave the cap on the radiator. As the engine comes up to operating temperature, watch the pressure gauge. I'm going to guess that combustion gasses (which are hot) will leak into the coolant and drive the pressure upwards, past the normal point. There is more to this procedure than I remember, so maybe some of the others will help.

Water doesn't have to get into the oil, nor does oil have to get into the water, for you to have a problem. If the head gasket is blown, you can have the problem. Likewise, if there is a problem with the block or the heads (and you ruled-out the heads), then you could see the problem when the gasses (bubbles) appear in the coolant. I don't see how you could be losing compression into the coolant, without seeing the engine overheat. If you aren't getting oil in the coolant, and you aren't getting coolant in the oil, and you're getting compression gasses in the coolant, it should be relatively easy to figure out where the problem is, or could be. It make take magnafluxing the heads and the block to isolate the problem. Good luck.
__________________
Member Nr. 2770

'96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed.

'69 C-10 SWB; 350/TH400 - in limbo

The older I get, the better I was.
ChevLoRay is offline   Reply With Quote
Old 08-26-2002, 08:10 PM   #5
Zkast
Account Suspended
 
Zkast's Avatar
 
Join Date: May 2002
Location: Olathe, Kansas
Posts: 929
What leads you to believe there is too much pressure?

If you think there is possible combustion gases getting into the cooling system there are a few ways to check this.
Preferred method:
Find a local automotive repair shop that has a 4 or 5 gas analyzer. Have them run a check on the recovery tank and cooling system. If they have never done this? Ask them to try... look for HydroCarbons. Normal will be 0 - 10 ppm (parts per million), If you see numbers upwards of 50 - 1000ppm then you most definatly have a Head/block problem allowing combustion gases into the system.

The other way (less accurate) is whats called a block test.
It uses chemicals to check for hydrocarbons in the coolant. Beware though, i've seen cars with HC's over 200ppm pass this type of test and blow the coolant out after a few minutes on the highway.

Can you give a little more info on why you think there is a problem? Maybe there is more to this than meets the eye.
Zkast is offline   Reply With Quote
Old 08-29-2002, 12:49 PM   #6
Bob Hinz
Registered User
 
Join Date: Aug 2002
Location: Maine
Posts: 6
Smile

Had somebody else look at it. A combination of timing and carb problems. The exhaust headers would glow after at running for 5 minutes. Got it all fix and it runs great now. Thanks for all the help.
__________________
Bob Hinz
Bob Hinz is offline   Reply With Quote
Old 08-29-2002, 03:15 PM   #7
StingRay
Senior Member
 
StingRay's Avatar
 
Join Date: Mar 2000
Location: Saskatoon,SK,Canada
Posts: 2,476
I have a real good buddy that has a rad shop that without a word of lie can sniff out hydrocarbons in antifreeze with his nose. Some good experienced rad guys develope the talent over the years so try a good rad shop. They usually have mechanical/electronic sniffers as well but the nose is cheaper and in my buddy Darrens case more reliable.
__________________
Saskatoon, Saskatchewan
Canada
StingRay is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 07:40 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com