white smoke only at idle when it feels like

[CoJo6.5T]

ok i replaced the starter the other day and after that fiasco i had to manually turn the motor over a couple times to make it turn over smooth but as i was doing it manually i heard a slawshing is that normal? and while it was running at an idle it pores white smoke but you drive it and it goes away after it reaches operating temp it stops no power loss but as soon as you start it up it has like a lope for just a second but it dosent do it all the time only if it sits for a while im confused it also while driving temp sores almost too 250 and just drops back down as fast as it went up it has a brand new thermostate,radiator,cross over housing,and it still bubbles into the resivor tank? im confused it might be the head gasket idk has any one else had these symptoms and know wat it is :confused:

[grancito]

Blown head gasket, or more likely cracked head. A blown head gasket will get worse in a short time, cracked head will normally continue to bubble air at the same rate.

[CoJo6.5T]

ok my next question is wat dose it mean when white smoke comes out of the dip stick it always did a lil bit but now its pretty rough

[grancito]

White smoke? or steam from water in the oil? Smell the exhaust white smoke to see if it is sweet, coolant smells sweet. Hold a mirror over the dipstick tube to see if water condenses on it. If the problem is progressing rapidly, it is a blown head gasket, but you will probably find cracks in the heads as well. You should have mentioned the bubbling in the coolant before, it is necessary to have all of the symptoms to diagnose correctly.

[Husker 6.5]

Yeah, Grant. I concur. I'd put money on at least one crack between intake and exhaust seats in one cylinder, if not more. It cascades, once you over heat and crack one, each time it overheats after that the original crack gets worse, and others develop in other cylinders from the stress.

[CoJo6.5T]

its only wen it starts thanks for the help or wen it sits for a while then as soon as it blows out going down the road it is done the longer it sits the more there is i cant really smell anything but raw diesel i might just take a compression test because if i drive it every day or like i said don't let it sit it is perfectly fine its only wen it sits overnight some times or a whole day is even thicker but take it a mile down the road and its all gone? thanks for your input i just want yo weed out all the small fixes first before i tear the heads out of it how hard is it could a back yard mechanic do it i have never took this ruck to a shop for any thing but paint and really don't want the bill for something that is just time consuming

[gregallen]

just a thought it sounds to me like one or more of the injectors are leaking down while it sits. Is it using water?

[gregallen]

probably not injectors i didn't read the entire post, didn't catch the part about bubbles in the rad. I used a product called Steel Seal ( just google it )on a 2005 duramax that i bought it was bubbling in the rad. and using about a gal. on water in 500 miles. i was a sleptic but decided to try it and it worked for me. I bought it with the problem intending to fix it and sell it. I sold it to a local and still see it driving around over a year and a half later. it might be worth a try.

[CoJo6.5T]

thanks that is alot of good news i really dont wanna tear the head off and its worth a shot but will it hold 15 psi of boost

[Husker 6.5]

Regardless of which product you buy to use as a stop leak, it is temporary at best. You have been up to 250* more than once and I'll guarantee that you've toasted one, if not both, heads. Trust me, BTDT with my '94. I used Morosso's glass block sealer to stop a leak. It held, right up to the first time it ran hot again (which '92-'96's were prone to do due to an undersized water pump) a few months later.

The temp went up a few months later to about 220* while I was pulling a Bobcat up a grade. About 12 miles later the heater started blowing cold (it was winter) and the temp gauge started climbing rapidly. I pulled over and dumped a spare gallon of antifreeze in and limped it off at the first off ramp into a station. Two gallons of water and antifreeze and all three jugs refilled with water later I pulled back on. In the 60 miles back home I went through 8 gallons of water. On the highway wasn't bad, but when I got to town and had to idle off-throttle in traffic it was pouring into the cylinders and the gauge would shoot up into 250*+ territory and I'd have to pull over and dump a couple of gallons of water into it.

Inspection of the passenger side head told the story. The initial crack was between the valve seats on #2. Yes, the sealer had sealed the crack. The problem is that sealers do only that, seal. You can not chemically rejoin the metal that cracked, only mechanical means (heat/welding) can do that. What's the weakest point in the casting? The crack. The crack in #2 had just opened up past the point where the sealer had sealed the initial crack and widened out. In addition, because of the heat stress from the multiple overheating cycles, #'s 4 & 8 also cracked across their seats as well as #'s 3 & 5 in the driver side head.

Basically, what I'm saying is this. If you use a sealer, know that no matter what the claim, it is a temporary solution for a mechanical problem. If you want it (sealing) to last as long as possible you must address the the overheating issue at the same time and upgrade your '94 to '97+ cooling specs with the '97+ high output water pump and dual thermostat crossover pipe with 180* thermostats at a minimum. Assuming that your radiator's core isn't clogged nor the exterior if full of crap blocking airflow, that should be enough to keep the engine together long enough to put two new heads on. You need to do both, because even if neither one (head gasket) or one isn't leaking, it has been heat stressed and it will fail eventually. $350 for a second head and doing them both at once is far cheaper than having to tear everything down a second time (with another gasket set) to replace the head when it fails later. Trust me, been working with 6.2/6.5's since the mid '80's.

[gregallen]

holding boost wont be a problem cause the duramax produces a lot more than the 6.5

[CoJo6.5T]

thank you but my true question is with a new radiator and crossover and thermostate why heat up then shoot down rediculously fast like it never happend just seems alot like a bad thermostate to me but you sound like all of you know alot about blown head gaskets and cracked block all i know is that no motor that is truely over heating rases that high and then drops perfect with out ever showing any sighns just wierd wat do you guys thinks thanks for the help any advise helps

[grancito]

Cylinder gases in the cooling system causing no coolant to heat the thermostat until steam is produced.

[Husker 6.5]

Cylinder gases in the cooling system causing no coolant to heat the thermostat until steam is produced.

And by then the temp gauge, with the sender in the front of the driver's head, is reading 230* or higher. The thermostat then finally opens and you get a surge of coolant and the gauge drops some, then the air pocket builds back up in the head and the temp climbs and the head stresses more and either the original crack widens, or more seats crack or both. It's a nasty negative feedback loop, once it overheats and either the head cracks or a head gasket blows to a coolant passage, every compression stroke you get 330 to 650+ psi (depending on boost pressure) of air being forced into the cooling system which creates air pockets in the heads and thus hotspots that stresses everything even more. At the same time, on the intake stroke, the coolant at 15 psi or more squirts into the cylinder, creating more room for air to be forced into the cooling system on the compression stroke following. At shut down, the coolant leaks into the cylinder(s) and that is the copious white smoke you see at start up.

See my comments earlier on this thread, CoJo. To get proper cooling, especially running with a performance tune and marine injectors, you must use the 97+ 130gpm water pump and dual thermostat crossover to flow enough coolant through the heads to keep them from overheating on '96 and earlier engines. You should also be running a 4" exhaust from the down pipe back, a straight 3" is only 1/4" larger than stock. It won't evacuate the exhaust from a tuned and injected motor efficiently, the back pressure will elevate the exhaust temp a hundred or so degrees and you won't spool up the turbo as fast.

You have been describing the perfect symptoms of a cracked head/blown gasket, you just seem to refuse to accept the reality. Do a cooling system pressurization test with a full cooling system (open the air bleeder on top of the thermostat housing when filling, when coolant starts running out without spitting, shut the bleeder and top the reservoir to the proper level). I'm willing to bet that the system won't hold 15psi, and that after it drops to zero if you pull all the glow plugs and use a light and mirror you will find coolant in at least one cylinder.

[Husker 6.5]

holding boost wont be a problem cause the duramax produces a lot more than the 6.5

It's not a question of how much boost pressure 6.5 vs. Duramax runs, it is a question of static compression and dynamic compression. Think back to Chemistry and Physics class in High School.

Follow the math. One Atmosphere is approx. 15 psi at sea level. A 6.5 runs 22:1 compression ratio (for math simplicity) while a Duramax runs about a 17.5:1 comp. ratio. So, at idle (0 psi boost) a 6.5 has 22 times 15 equals 330 psi static cylinder pressure. A Duramax is 17.5 times 15 equals 262.5 psi static cylinder pressure.

Now lets add boost. A 6.5 at 15 psi boost is one atmosphere of boost pressure, so 30 psi times 22 equals 660 psi dynamic cylinder pressure. A Duramax runs about 20 psi boost stock, so 35 psi times 17.5 equals 612 psi dynamic cylinder pressure. The Duramax actually runs LESS dynamic cylinder pressure than a 6.5!!

So, as you can see GregAllen, the dynamic cylinder pressures between the 6.5 and Duramax are virtually the same, with the 6.5 running almost 50 psi more and that is not a factor per se for your Steel Seal working in a 6.5; however, sealers of any sort are temporary at best in a 6.5 for the reasons I outlined two posts above earlier.

So why, you may ask, can you chip a stock Duramax and run 35-40 psi without blowing head gaskets when the 6.5 does if it runs 17-20 psi continuously? Simple, design. 6.5 has 5 TTY head bolts per cylinder where the Duramax has 6 high tensile, larger diameter head bolts per cylinder which results in a much greater clamping force and keeps the head gasket from blowing out.

[gregallen]

I still think that the steel seal is an option in some cases. Like that of my duramax, it was small enough that after doing diagnostic procedures (removal of glow plugs, pressurising the cooling system for 30 min. than turning the engine over to see which hole got wet.) we could not determine whitch head or side had a problem that Gm said that it might be hard to determine where it was even after pulling it all apart. But i agree if the problem is real bad it needs to be fixed in the proper manner.

[Husker 6.5]

Yes, in some cases I agree. But with 6.5's in general, and with the symptoms that were described by CoJo especially, sealers of any sort are not a solution just a very temporary band aid at best. When a 6.5 starts the symptoms, the only cure is to pull the heads and go from there, including a cooling system upgrade on 92-96's, to stop the problem.

[CoJo6.5T]

ok so let it sit and pull the glow plugs and look for coolant correct the reason that i dont want to pull the head is it is my daily driver and i just want a way to find out if it is diesel wen it sits from the injector or coolant it smells like raw diesel on start up very strong the temp is the only reason that really makes me consider the head or head gasket i love this site its nice being able to ask questions and get a answer or and idea thank every one

[gregallen]

is it using water? might be hard to tell if is getting hot and boiling over