• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

D9G D343 Pressure in Cooling System

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
Last fall the D9G (SN:66A7869) that we've been running with started burping out coolant from the pressure relief cap when in operation. We thought that we were having a heating issue and because we were close to the end of the job we just brought the machine back to the shop to give it a once over.

We pulled and replaced the relief cap after finding that it was corroded. We also found a few other leaks on the cooling system we then repaired and thought we were all set. We had a new job come up and decided to put the machine back to work pushing pans. Before taking off to the job I put the machine out back to push against some dirt mounds to get it up to temp. Sure enough the relief cap starts to burp out coolant. The odd thing is that the motor was not hot, not even close to being hot. What I did notice is that the cooling system pressure gauge was showing high pressure in the system. When the pressure gauge would get up into the high side, it started to burp. I let the machine cool off and checked the coolant level and the color only to find the radiator full and that it was still green as new. I ran the machine some more and the pressure gauge would build up pressure as I ran the machine, burp a little, and then stop for a while until I really worked the machine hard with long hard pushes against the mound and cycling the motor rpm up and down like you would pushing pans. If I stopped a for a few minuets the pressure would come down to normal. At idle the machine would show normal pressure.

So here is the question is this a simple case of a bad head gasket? Could it be a bad seal on the precombustion chambers in the head? I would think that if the head gasket was blown I would see soot in the coolant and the pressure would stay elevated? I'm a little stumped here. What do you guys think?
 

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
Do you have a kit to test for the presence of combustion gases in the coolant.?
I don't, however a quick google search says I can get one pretty quickly and cheap. What should I look for on the test results?
 

excavator

Senior Member
Joined
Oct 16, 2006
Messages
1,445
Location
Pacific North West
Nige and a few others on this forum likely have much more knowledge on these than I do but if I remember correctly the D343 was known for cracking heads, usually a bunch of tiny cracks that were very difficult to repair. I worked on one in an old 988, sent the head in to be welded up and when I re-installed it we still had a slight amount of bubbling. I called the company in Portland, Oregon who did the head and they told me to get 4-5 tubes of silver solder and dump it in. It worked, not necessarily the right way to do it but like I said, it worked. I'm not suggesting you try to repair your machine with silver solder but you might want to be prepared to find a cracked head when you pull it.
 

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
Nige and a few others on this forum likely have much more knowledge on these than I do but if I remember correctly the D343 was known for cracking heads, usually a bunch of tiny cracks that were very difficult to repair. I worked on one in an old 988, sent the head in to be welded up and when I re-installed it we still had a slight amount of bubbling. I called the company in Portland, Oregon who did the head and they told me to get 4-5 tubes of silver solder and dump it in. It worked, not necessarily the right way to do it but like I said, it worked. I'm not suggesting you try to repair your machine with silver solder but you might want to be prepared to find a cracked head when you pull it.

Hopefully it doesn't come down to this but this is good to know that these engines have known problems with the head. Like many older machines, I am finding that parts are becoming scarce.
 

Bluox

Senior Member
Joined
Jun 19, 2010
Messages
1,960
Location
WA state
Hopefully it doesn't come down to this but this is good to know that these engines have known problems with the head. Like many older machines, I am finding that parts are becoming scarce.
Drain about 2 gallons of water out of radiator and try it.
What do the temp gauge read?
Did you replace the pressure valve under the bolt on cap?
Did you replace the water regulators in the head?
That tractor should have a D353 engine.
You don't need any testers just warm up the motor shut it off and fill the radiator full ,start motor and watch for bubbles.
Bad Bob
 
Last edited:

Coaldust

Senior Member
Joined
May 9, 2011
Messages
3,292
Location
North of the 60
Occupation
Cargo Tanks, ULSD, RUG, Methanol, LPG
Once you confirm the presence of combustion gasses, I would consider pulling the pre-cups and inspect. Could be gaskets, a cracked pre-cup or a “worm hole”.
 

Coaldust

Senior Member
Joined
May 9, 2011
Messages
3,292
Location
North of the 60
Occupation
Cargo Tanks, ULSD, RUG, Methanol, LPG
You can often remove all the mystery about diagnosing combustion gas in the cooling system with the Cat bottle test. Plus, obtain quantitative data you can compare to spec. A 5-gal bucket, Nalgene bottle and some 3/8” tubing. Cheap and relatively easy.

0183616E-658C-450B-86C6-6EDDD6AA69A5.jpeg
 

Cmark

Senior Member
Joined
Jan 2, 2009
Messages
3,176
Location
Australia
I give another vote for checking the precups.

img_0882-jpg.223738


https://www.heavyequipmentforums.com/threads/cmarks-random-photo-thread.77839/page-9
 

John C.

Senior Member
Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
Plugged radiator cores can cause the high pressure on the top of the radiator as well. They will also cause a vacuum or lower pressure at the inlet of the water pump causing boiling coolant that is never seen on the temperature gauge. I agree that D9 engines were D353 models. I also agree on the pre-cups.
 

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
Drain about 2 gallons of water out of radiator and try it.
What do the temp gauge read?
- We are only getting up to about 170F to 180F based on the after market gauge we installed. Its a universal gauge and the gradation on the lower end are difficult to read accurately but the dial was under 190F without question.
Did you replace the pressure valve under the bolt on cap?
- Yes. We bought an entire assembly from Cat. part number 7S-4327
Did you replace the water regulators in the head?
- This we have not done
That tractor should have a D353 engine.
You don't need any testers just warm up the motor shut it off and fill the radiator full ,start motor and watch for bubbles.
- We did check the radiator for bubbles and were not seeing any when checking the coolant level after having pushed against some piles and the coolant was not bubbling.
Bad Bob
 

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
Once you confirm the presence of combustion gasses, I would consider pulling the pre-cups and inspect. Could be gaskets, a cracked pre-cup or a “worm hole”.
If we get confirmation of the gasses in the coolant then we will definitely pull these out to check them out.
 

Bluox

Senior Member
Joined
Jun 19, 2010
Messages
1,960
Location
WA state
When you check for bubbles fill the radiator running over full.
The correct temp. gauge shows the temp corrected for pressure read on the pressure gauge.
If the precups are leaking they leak both ways so you would be using water and at some point the motor would Hydo lock.
Have you pressure checked the cooling system yet?
If you find no bubbles drain radiator down about 2 or 3 gallons and run it to see if it still purges water.
Bad Bob
 

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
When you check for bubbles fill the radiator running over full.
The correct temp. gauge shows the temp corrected for pressure read on the pressure gauge.
If the precups are leaking they leak both ways so you would be using water and at some point the motor would Hydo lock.
Have you pressure checked the cooling system yet?
If you find no bubbles drain radiator down about 2 or 3 gallons and run it to see if it still purges water.
Bad Bob
Were working on getting the scrapers all back going, we've had a rough week these past two weeks on failures, and once they're up we'll start trying out these checks.
 

631G

Senior Member
Joined
Apr 27, 2008
Messages
336
Location
Georgia
Occupation
Civil Superintendent
Well we finally got the old D9 into the shop and get the chambers pulled out. Sure enough they were pitted and corroded pretty well. Not as bad as this but close enough. Replaced all 6 of them and the glow plugs for good measure. Costex had all the parts and not priced as bad as I thought having compared to what Cat wanted for them.

Bad thing is that we still have pressure in the radiator. So head gaskets here we come. Good times all around…
More to come.
 
Top