First, thanks for the help and hand-holding through my oil cooler failure - no more oil in the coolant, and oil analysis shows no coolant in the oil.

Still have a minor coolant leak - I think I have it localized to the thermostat seal rings but not sure.  Could be head gasket but no indication of gas in the cooling system - it is an external leak, whatever.

Did y'all know that antifreeze fluoresces in black light all by itself, without any fluorescent dye added?  Weird.

Anyway, temperature gauge was acting like the thermostat was stuck open - taking forever to even budge off the peg and never really getting up to temp, so I took changed the thermostat out.

The old one had rubber pieces stuck in it, keeping it from closing.  Could not figure out where the rubber sheet-like stuff came from until my wife found a picture on the internet, showing that the stock thermostat has this rubber wrapped around the body of it.  Laid out the pieces on the bench and it sure looks like that is where it came from.

Auto parts store Stant 180º thermostat did not have the rubber wrap or look quite the same; put it in anyway.  Re-used the two rubber seal ringss that hold the thermostat in place (since I didn't have new ones and it was a Sunday).

Now the engine gets to operating temperature just fine, but if I watch the gauge I can see the thermostat open, temp drop some, then come back up to 180º, then drop some again - like, the old thermostat had the rubber coat on to keep it stable and not have to open and close so much.  Temp never goes high, never drops real low, just cycles.

And I think the leak - maybe a cup every week or so - is from the seals I re-used.  Damp there, and black light makes it fluoresce just like new antifreeze/water mix I use to top up the overflow tank.

So my question is, do you think this thermostat is ok, or should I get "the right one" (with the rubber blanket on it) and new seals, and change it out?

I value your opinions.  Thanks in advance!

Andrew

Except the leak,  it sounds normal. 

Cool, Thanks!

Either the liquid is coming out the seal rings, or from the head.  Can't you tell I'm just itching to put a head gasket in? Even if it does not need one?

I think resealing the thermostat is the first step.  If that fixes the leak, that was where it was leaking...

Sounds normal. 

The 180° thermostat opens at 180° but isn't full open until 198° so fluctuation is to be expected. 

Thanks, I'd never noticed it fluctuating before and was worried I'd messed up by putting in an "auto parts" thermostat instead of one made like the original.

I still don't understand the rubber coat, but it is only one of the many, many things I don't understand...

Just a sealer. I had to put some RTV or some sealant on the thermostat housing to keep it from weeping. Picture of the leak?

No picture yet, let me 1) Gunk the engine down, 2) run it for a few days, 3) try to get a photo using black light.  I don't want to make too much of a big deal about this, but if I get the leak fixed it will be time to put a radio in the truck.

Right below the thermostat is a common head gasket leak area.

If that is the issue, welcome to the *Need a Head Gasket* club!

Thank you Cowboy, this is exactly what I'm worried about.

I've read enough on the Internet to know it is a common leak area and have been worried.

But since the truck runs fine, oil analysis is excellent, and the leak is so slow that there is never a puddle, I wonder whether it is wise to fix the head gasket leak or just monitor it (if that's what it turns out to be).

Also - I want to know how to be sure it is the head gasket.  Seems like if I replace the seal rings on the thermostat and the leak is still there, it is almost certainly the head gasket.  Or is there another way to tell for sure?

I've never dealt with a leak in that area, but my general leak finding method is dry the area off completely, and then put down some baby powder or the like.  Then just watch it like a hawk and see where it gets wet first.

If it is a head gasket, you may be able to get away with just re-torquing them.  IIRC, Cummins specs are 60 ft/lbs on the two shortest length bolts, and 90 ft/lbs on the longest ones.  Then give them all another 1/4 turn (90*).  However most guys just do 90ft/lbs plus 90* on all the bolts for more holding force for their performance needs.  If you decide on the re-torque method, let me know, there are a couple tricks to do it right.

On the plus side,  I've got compression in my radiator, and coolant down the exhaust side of the block.  So I need to change my gasket.  I've been wanting to do that for a while to give me a chance to port the head.  There are basically 3 stages of porting, and the 1st stage is stupid easy, and helps with flow across the board.  I'll probably give it a stage 1.5-2.  

http://articles.mopar1973man.com/2nd-generation-12v-dodge-cummins/69-air-intake-exhaust/499-don-s-head-porting-extravaganza

I don't think there is a thermostat available for a 12v that doesn't fluctuate. I bought one of the eBay thermostats that are not supposed to fluctuate but it did too,  just the way it is with the oversized cooling system.

I have no problem with the fluctuation, as long as it is not damaging anything.  I worry about causing problems by using "the wrong" parts or whatever.

If I have to change the head gasket, I'm worried about getting dirt or contamination into something, because it is a diesel.  If it were any kind of gas engine, from a lawnmower to a V8, I would have no qualms about a head gasket.  But there just seems to be so much more to potentially screw up on a diesel... I worry about cleanliness and dirt in the injectors and so forth - maybe this is just "fear of the unknown".

Anyway, thanks for the feedback on the thermostat!

Andrew

There are a lot more reported issues with non-Cummins  thermostats so watch for them, but if it works it works. 

Cowboy, you are right; I'm almost certain it is the head gasket.

No pictures but I cleaned it real well, dried, added fluorescent dye to the radiator, and started it.  Let it run at idle a few minutes.  I see the leak with my twisty inspection mirror and it sure looks like the head-to-block joint, near but not at the thermostat housing.

It has lost almost a gallon of coolant in the last 5 weeks.  If I were confident it would stay at that rate, I'd wait til plant shutdown in December and replace the head gasket.

Anyway I'm ready for your tips about re-torquing the head - probably ought to start a new thread on this but we're here now.

Service Manual says what you said so I'm questioning how to go to 90 ft-lb + 90 degrees, if they are already there?  Is there a torque (like, 100-125 ft-lb) that would be ok but not too much?

From the book, the head gasket looks not-too-hard, but I have questions.

1) Do you re-torque it after it has been run for a while, and if so, to what value?

2) Do the injectors need to come out of the head, or can I just pull the metal lines and leave the injectors alone?  Concerned about dirt.

3) How imperative is it to pull the valves out of the head once it is off?  No valve job in 582k mikes, but does not act like it needs one.

You can tell I "want to make it right" on one hand, and "don't want go go hog wild" on the other.

...and my buddy knows a diesel mechanic who works on his 24 valve, and highly recommends him, and says I'm too old to keep doing this all myself.  I could afford to have it done but am reluctant - ego too involved.  May be time to grow up, let the man make a few bucks on me, spend the time with my wife or at the rifle range instead of in the barn with the truck apart...

As always - Thanks!

Andrew

Don't worry about the new thread, most us read all the threads anyhow. haha

Do you plan on re-torquing or replacing the gasket?

Either way, when you go to torque the bolts, make sure to use the sequence in THIS picture.

If you're re-torqueing, just remove the valve covers and injector lines including the small injector return line.  Then just start in the center as the picture above shows, remove a bolt, put a small dollop of a good grease (I use some red synthetic grease), and then torque it down, go to 90 ft/lb's plus a quarter turn.  That will put you around 125-130ft/lb's reason for the 90* thing is because your torqueing the bolts to their elastic state, so it's more accurate to do it that way.  If you feel like any of the bolts are getting buttery, stop, take it back out and replace it.

Only reason to pull the injectors out is they protrude on the bottum, so if you plan on setting the head anywhere, either be careful and use blocks when setting the head down (my favorite) or pull the injectors.  if you leave the injectors in place, make sure when you pull the head, it doesn't "drag" on the block.

I'm not the one to comment on the valves, but I would atleast pop them open and check the seat condition.

If you're worried about dirt getting in, there are only two main places to worry about, the Injector Pump and the Inlet to the Injectors.  Get a pack of these and they'll screw right into both the injector pump and injectors to protect them from dirt and damage to the threads.  http://www.ebay.com/itm/20-Chrome-Bulge-Acorn-Wheel-Lug-Nuts-Pontiac-G8-M14x1-5mm-1-4-Standard-qw-/291535817688?hash=item43e0e38bd8:g:aakAAOSwLVZVx7WJ&vxp=mtr

 

 

 

 

Edited November 15, 20159 yr by Cowboy

Thanks Cowboy!

Leaning toward a head gasket instead of re-torquing.

I'm over my reluctance to pull out the injectors.  Thinking about it, you are clearly right that the point is to keep trash out of the injector pump and injector inlets.  Leaving them in the head will do nothing towards that.

Been reading on the Internet and darned if I can find the holes in the cowl that are supposed to be there, to get the back pushrods out.

I do have an engine crane.  If my engine stand were not cheap Harbor Freight, suitable for small 4 cylinder engines, I'd be tempted to pull the engine out so I could work on it without tearing up my back or risking dropping trash into it.

At this point I feel like, if the head does not need machining, this will be a relatively simple, if time-consuming, job.  If it is warped I need to figure out where to take it and how to get it there.

And on Monday I will call the mechanic that my buddy recommends, and ask him for a time and cost estimate.  If it is warped, he can deal with it!

Thanks and we'll see how this develops.  I feel like I ought to be grateful for a chance to do something I've never done on a diesel.

Andrew