Engine/Transmission (1998.5 - 2002) in english please...

[favord]

Help me out with this one. Took my truck into the local Intermtn. Cummins to have head gasket checked out. I was pretty sure it was faulty after blowing out all the coolant, overheating, etc. while towing a heavy load in the mtns. this weekend.



I'll just post their report: "checked blowby. found engine has 10" of blowby which is the maximum published limit by cummins specs. the elevated blowby could be due to the fact that there is 10psi more boost being fed to the engine than factory spec allows. checked for combustion in coolant. no evidence at this time there are any problems"



I guess I'm still not convinced I don't have a problem... hard to see antifreeze all over the engine compartment and not think somethings wrong. Apparently my engine is fine for stock parameters... but I'm not running stock parameters. I need the truck for towing fairly regularly and am not real enthused by this report - I'm not gonna hit the road with a lot of confidence. I think until I get this figured to my satisfaction I may do the unthinkable and de-tune a little by switching back to the factory boost elbow and limit my boost.



Anybody have any other interpretation of these findings. They didn't seem to impressed by my mods to the truck.



Thanks for any info.



Doug Favor

 

[illflem]

How much boost you running? You won't gain anything but heat over around 36 psi.

You might want to replace your radiator cap and make sure the line to the coolant reservoir is clear. Of course make sure the radiator isn't full of bugs and your fan clutch isn't shot.

 

[favord]

Thanks. My max boost is around 32#. Radiator cap sounds like a good idea. Radiator does look clean to me. How do you check fan clutch??



Do I gather from your comments you would feel the head gasket is sound to my boost level from the comments the Cummins mechanics gave me? I guess I felt like they told me my motor is sound to factory specs only... above that they didn't or couldn't comment I guess. . ?

 

[illflem]

With your engine off and cold the fan should spin with slight resistance but not freewheel. Before it overheated you should have heard the fan engage like a fighter jet taking off.

From your description of what Cummins did it almost seems like they only checked the engine but not the cooling system??? My feeling is your boost level and head gasket (from Cummins tests) is fine.

 

[Hohn]

Originally posted by favord

. . checked blowby. found engine has 10" of blowby which is the maximum published limit by cummins specs. the elevated blowby could be due to the fact that there is 10psi more boost being fed to the engine than factory spec allows. checked for combustion in coolant.

The 10" number is inches of mercury (Hg). It's a measure of pressure. Standard atmospheric pressure is about 14PSI, or 29. 92 inches of mercury. It comes out to about 4. 7PSI.



They're saying that your crankcase is pressurized by 4. 7psi more than it should be (under ideal conditions), and they're attributing it to your running more boost. .



Hohn

 

[ynot]

Actually, they are saying it has 4. 7psi TOTAL, not over spec. It has 10 in. Hg. total monometer pressure, which is the highest alowwed spec by the engineers on a stocker. Tweaked motors have tons more (I can blow the top off my "cath-all bottle" at 50psi and over). These engines have lots of blow-by at high boost, as do most other diesels. No biggy. A good manometer reading has to be done under full load, so if they were just revving it up on the floor, the test was inaccurate anyway. If your head gasket let go, you'll be leaking oil down the side of the block real soon... To bottle check the motor, you have to duplicate the scenario at time of failure. Block the radiator with cardboard to reach the temp it was at, then load the engine. You can use a dyno (prefered method), or attach a hose to the radiator overflow hose and run it into the cab thru the window. Insert hose into the bottom of a clear glass or plastic "Coke" bottle half full of water, duplicate heat and load, look for air (gas) bubbles blowing into the water. That will show cylinder pressure leaking past the gasket into cooling. Cylinder pressure leaking past to the oil side (crankcase) will just start making things leak oil that didn't before. If it has more than 100,000 miles on it and you're usually towing heavy, it probably let go. Wash the motor down real good and run it a day. You'll see water or oil leaking out around the #1 or #6 corner of the head gasket if it puked. Not too bad to fix, just a lot of hanging over the top side and hand tools. Not enough clearance to blow thru it with good air tools. Hope that helps. Good luck... T

 

[willyslover]

and to add to Tony's response... a stock gasket with your mods. looks like it should be a good replacement... . 32 lbs of boost isn't that big of a deal on a stock gasket in a 98. 5... just be sure to follow the torque recomendations... and a retorque after running a couple cycles of the hills

 

[Idaho CTD]

You might have an oil analysis done to see if it is leaking into the oil. I think they (DC) pressurized my coolant system to 18psi for testing so that might be another possibility.

 

[Hohn]

Originally posted by ynot

Actually, they are saying it has 4. 7psi TOTAL...

That's what I was saying. Ideal being zero pressure.



Hohn

 

[jtisdale]

I agree...

Originally posted by Idaho CTD

You might have an oil analysis done to see if it is leaking into the oil. I think they (DC) pressurized my coolant system to 18psi for testing so that might be another possibility.

Get the oil analyzed. But in the mean time, find someone with a coolant system tester. This handy little unit will pressurize just the coolant system and then you can look for external leaks. However, but the sounds of your post, you already know you have one.

It may be possible for the coolant to only leak "out" and not "in". Maybe someone will hypothesize on this theory.

 

[Hohn]

I would guess that contaminated coolant is far more likely than coolant in the oil. The coolant operates at less pressure, and would seem to be more likely to be the victim than the culprit.



my 0. 02



Hohn

 

[jerrethomas]

Originally posted by ynot

Actually, they are saying it has 4. 7psi TOTAL, not over spec. It has 10 in. Hg. total monometer pressure, which is the highest alowwed spec by the engineers on a stocker. Tweaked motors have tons more (I can blow the top off my "cath-all bottle" at 50psi and over). These engines have lots of blow-by at high boost, as do most other diesels. No biggy. A good manometer reading has to be done under full load, so if they were just revving it up on the floor, the test was inaccurate anyway. If your head gasket let go, you'll be leaking oil down the side of the block real soon... To bottle check the motor, you have to duplicate the scenario at time of failure. Block the radiator with cardboard to reach the temp it was at, then load the engine. You can use a dyno (prefered method), or attach a hose to the radiator overflow hose and run it into the cab thru the window. Insert hose into the bottom of a clear glass or plastic "Coke" bottle half full of water, duplicate heat and load, look for air (gas) bubbles blowing into the water. That will show cylinder pressure leaking past the gasket into cooling. Cylinder pressure leaking past to the oil side (crankcase) will just start making things leak oil that didn't before. If it has more than 100,000 miles on it and you're usually towing heavy, it probably let go. Wash the motor down real good and run it a day. You'll see water or oil leaking out around the #1 or #6 corner of the head gasket if it puked. Not too bad to fix, just a lot of hanging over the top side and hand tools. Not enough clearance to blow thru it with good air tools. Hope that helps. Good luck... T

if u can find a well known mechanic he may have a headgasket checker i think that's what snap-on calls it. it has two or three stages of fluid in it. you put a rubber tip over where the raditior cap goes and squeeze the bulb. it almost looks like a turkey baster thing. the fluid reacts to carbon dixiode i think, which is not usually present when the head gasket is "good" one of my friends has one of these and they really work good.

 

[ynot]

Hohn, oil in the water only happens when the pressure port of the gasket ruptures, or it breaks a head bolt and totally lets go between water and oil ports (or the oil cooler pukes), which is rare. Drain down oil is static. They rarely mix anyway, unless it really lets go, then it isn't even drivable... Jerret, those testers are pretty junk. There has to be mass amounts of carbon to detect, in which case it is naked eye visible as a black gummy film on the cap. Best way to find it is duplicate the failure scenario, however possible... jtisdale, leaking coolant goes where it wants to. It will move around the plates of the head gasket, but to leak back inside, it has to move past another broken seal area. To put water in the oil, there MUST be TWO broken seal areas of the gasket, one oil, one water. That's why they leak to the outside. One ruptures (coolant or oil), and it goes to the lowest pressure point to escape, which is out, as there is no perimeter seal on a B head gasket. Hope that helps... T

 

[Shooter]

Do not overlook the t stat

I had a similar problem. Only puked coolant on pass side of engine while towing 5+%grade above 2200 rpm in 80*f . coolant temp would rise to 210, fan would come on and collant would cool down to 200. After a few grades the temp would rise and not come down below 210 and would steadily rise. Coolant loss would be substancial in a short time. No heating and collant loss below mentioned paramiters.



It was the thermostat gasket ( O ring ) that would start leaking at high temp and pressure. kStatic pressure 18psi test at 80* ambient revealed no leak. 18. 5psi leaked like a sive . Retorqueing the themo housing would not seal the leak. Replaced stat, no more problem.

Don't overlook the t stat. It is probably time to replace it anyway, Itis only about $13 and takes 10 min with no draining coolant and about 1/2 gal collant to top off after replacement.

 

[Shooter]

Do not overlook the t stat

I had a similar problem. Only puked coolant on pass side of engine while towing 5+%grade above 2200 rpm in 80*f . coolant temp would rise to 210, fan would come on and collant would cool down to 200. After a few grades the temp would rise and not come down below 210 and would steadily rise. Coolant loss would be substancial in a short time. No heating and collant loss below mentioned paramiters.



It was the thermostat gasket ( O ring ) that would start leaking at high temp and pressure. kStatic pressure 18psi test at 80* ambient revealed no leak. 18. 5psi leaked like a sive . Retorqueing the themo housing would not seal the leak. Replaced stat, no more problem.

Don't overlook the t stat. It is probably time to replace it anyway, Itis only about $13 and takes 10 min with no draining coolant and about 1/2 gal collant to top off after replacement.



Standard cooling pressure test is done at 18psi and red line is 20