Injector cup seal vs. head gasket, how to isolate?

[Mark Rinker]

I am experiencing low coolant lights illuminating on both of my trucks. So far, its very infrequent - maybe every 3,000 miles and it only takes 1/3 to 1/2 gallon to bring the level back to normal.

- Neither truck is visibly leaking at the hoses, waterpump, or on the ground.
- Neither truck has any signs of white smoke.
- Both trucks have new injectors, ~10K miles ago.
- Both have new thermostats.
- Both have new coolant overflow tank caps.

Neither did this before the injector/thermostat/glow plug replacements last fall. The '01 got a new waterpump shortly after. The '02s waterpump is original. Both trucks have been doing this since. At first, I thought it was just air in the systems, working it way out.

Now I wonder if they both aren't using/leaking/evaporating coolant somehow. Could it be head gaskets or injector cups on BOTH trucks, after having similar service? What are the odds of that?

I am leaning more towards something wrong with the service given, bad thermostats, or ??? It just doesn't make sense that both trucks would start doing this at the same time - when neither of them used a drop of coolant before. The '01 does seem to be using slightly more. However, it tows heavier and may simply be getting more miles on lately.

Also, I have tried purging the systems of air per the Helms manual instructions below on both trucks, with no results. (The coolant level stays stead in the overflow tanks during the 3K cycles with the overflow tank cap removed.)

> Per the Helms manual the air is purged by cycling the engine to 3000 RPMs several times with the cap off and thermostats open (engine hot). At this point I
> close the cap and take a ride around the block and top off one more time. Each time the engine is cycled to 3000 RPMs, the coolantlevel in the expansion ?
> tank drops, then rises as the RPMS fall. When all the air is purged the coolant level in the tank doesn't drop as the RPMs are cycled.



Opinions?

[More Power]

A slow coolant leak could result in evaporation before it can drip off the engine. So, you'll need to look really hard all over the engine to see if you can identify a pink crusty buildup.

If you're sure there is no external leak -

After sitting overnight, pull all eight glow plugs, one at a time, looking for moisture on the glow plug tips.

If you find a cyl with moisture, I'd have the dealership reseal that injector cup seal.

If the problem is unchanged, I might consider a head gasket - but not till after the above has been dealt with. :)

Jim

[Mark Rinker]

Could the injector cup seals be affected by the recent injector service? i.e. Is it more likely age/miles or injector installation related?

Would an oil sample analysis yield any useful information, before pulling glow plugs as you suggested?

[Kennedy]

Could the injector cup seals be affected by the recent injector service? i.e. Is it more likely age/miles or injector installation related?

Would an oil sample analysis yield any useful information, before pulling glow plugs as you suggested?

Yes absolutely. Air in the cooling system (blowby past cup seals or head gaskets) can cause this as well as the heat/temp incident described a few days back.

The heater "cold" tube has also been known to seep where the hold down bracket is welded on. Pull the wheel liner and check this out.

You have to look close, but you can see this tube and bracket/bolt above the IC pipe in this picture:

http://www.kennedydiesel.com/images/Block_Heater_cable_storage.jpg

[Onebigcanuck]

I had a similar problem, taped a plastic bottle to the overflow hose and found the liquid been blown out there.

Hope it's a easy as mine was.

[More Power]

It's been reported here in the BB that an injector cup can pop out or become dislodged when an injector is removed. This messes up the sealant that seals the narrow end of the cup to the head. In those situations, the cup should be removed and both the cup and mating surface on the head cleaned to accept a fresh coat of sealant.

I can't help but wonder if dealer techs reseal all of the cups when they change a set of injectors or if they hope the seals are undamaged? :(

Jim

[Mark Rinker]

Well, today I finally found a small puddle of coolant under the 2002. I had already inspected and ruled out JK's idea of the heater return line - there was no apparent leak there.

For now, my theory is its the water pump starting to go at 186K miles. I have one already on the shelf, just for this occasion. (New OEM part found on Ebay - $80!!!)

As for the 2001, I haven't had time to dig any further. Hoping it will be something similar - I know there was an issue with some fitting sealing properly at the water pump during the recent install. Maybe its leaking under load. It needs new front brake pads and rotors, so I'll probably let the dealership fix that necessity, and ask them to 'find the leak' at the same time. If its nothing external to the engine, then we'll have to dig in deeper.

If it is an injector cup - I think that will need to be the dealer's fix as it never used coolant before, and its been using coolant ever since the injectors were replaced.

MP - would an oil sample analysis detect coolant in the oil if it were an injector cup seal?

[Mark Rinker]

Well, I think both of the low coolant situations have been resolved...

2002 - New water pump, as anticipated. Mechanic slipped when removing crank pulley and knocked a hole in the radiator - they paid to have it sent out for repair and a chemical flush. Radiator shop reported that the fins were VERY dirt clogged, so the next time I get a chance, the 2001 radiator is coming out for the same treatment. 185K worth of bugs, dirt, and road grime.

2001 - Leaking coolant at the block heater. Replaced heater unit and resealed.


Crossing my fingers - hopefully this takes care of both situations without any major R&R like injector cups or head gaskets...JK the mechanic that did both of my injector jobs said the injector cups were removed, cleaned up, loc-tited and sealed back in place during the service.

[Mark Rinker]

In previous posts I had reported that my '01s coolant loss was corrected when we found and replaced a leaking block heater. At that time, BOTH my '01 and '02 had coolant loss problems, the '02 got a new water pump and appears to have remedied its problem.

Since that time, the coolant loss problem on the '01 has returned with a vengence. After refilling, it will quickly puke out the first gallon from the overflow tank, illuminating the LOW COOLANT warning, then run with whats left, never overheating, and only slow to get the thermostats open for cab heat. I would have it parked, but we have been BURIED in snow, and have been personally driving it and getting our work done, adding coolant every morning when the truck has had time to cool off. Truck has never been hot. If not for the LOW COOLANT light, and eventually the slow heat symptoms, you'd never know there was an issue going on - except maybe all the pink down the side of your truck, and the spot on the driveway where I warm up every morning.

The driver side radiator hose is always under major pressure, anytime the truck is warm. The GM techs here have pulled all glow plugs and done the 'white paper' test and found no coolant present. They have also used the CO tester on the overflow tank on two separate occasions, and tests are negative or inconclusive (blue dye turns brownish over time, but not yellow as it should.) We even replaced the overflow tank as it was crusted and at one point it seemed plausible that the indicator could be false. (This was when it was using 1/2 gallon every 3,000 miles - not 1 gallon in 50 miles...)

QUESTION OF THE DAY: Is there any other conceivable way that I could have these symptoms OTHER than a head gasket or injector cup seal leaking?

How about a bad thermostat (replaced recently) from the factory? Would that cause the initial coolant-puke and then settle down and act normal with the coolant level low? Also - why no white smoke at exhaust or running problems if there is a connection between combustion chambers and coolant passages???

@#$@#%$%$%^% (By the way the transfer case is leaking as well. Not feeling the love from my '01 these days as my pretty white snow covered driveway is a calidescope of pink, red, and greenish UV dye right now.)

[Tough Guy]

Thats too bad....maybe you shouldn't be so hard on your stuff? :D J/K!

My WAG is HG's or IC's.

Chris

[Mark Rinker]

They get worked for sure. Especially this one.

[More Power]

Part of the reason for using two thermostats is redundancy. So, it's unlikely to be the cause.

My guess is you have a bad head gasket. I spoke with another member from WA state a couple of days ago. His engine developed almost the exact same symptoms as yours. After tear-down, they discovered a bad head gasket.

His truck is being used as a work/service vehicle (albeit a nice one), which is a dually equipped with a custom flat bed and a 3K welder, among other things. The fully-equipped truck weighs about 11K+. He'd been using a performance module with a 60hp setting, and was a little apprehensive about re-installing it once the gaskets had been replaced. In the end, we agreed he should run the truck without any performance mods for a 3-4,000 miles after the repair to see how it goes. I don't think the 60hp module was the cause, but.....

Jim

[Mark Rinker]

I agree that all indicators point to a bad head gasket - but why no high CO levels in the coolant?

If I am headed down the path to replacement - and plan to continue to run with additional power and heavy loads, are there better aftermarket gaskets and/or bolt sets I should investigate?

What do the high-power racers use? Heck, as long as we are at it - what about a set of performance heads? :) :) :)

[Mark Rinker]

I would like to hear from anyone that has had coolant system pressurization and loss through the overflow tank - especially at idle.

Also, would like to hear from anyone that has had an injector cup seal fixed WITHOUT head gasket replacement. Very interested to hear your symptoms and the troubleshooting used by the dealership to isolate the problems.

It seems that most here with coolant system pressurization problems have received head gasket replacement - even though injector cup seals are always presented as a possible culprit for this problem. Could the head gaskets have been unecessarily replaced and the bad injector cup(s) repaired, requiring engine removal, instead of resealing them as is done whenever injectors are replaced? Head removal is much more labor intensive - often time the entire engine is removed to 'simplify' the process!!!

This is important on my truck, as the problem started soon after injector replacement. If an injector cup was resealed improperly, then I would expect the dealer to make it right. If its a head gasket, I'll be getting out my wallet. Again.

Any smart ideas on how to manage this to a good conclusion with my dealership? They are reasonable people, just need a troubleshooting method before we pull the engine and replace two good head gaskets on my dime - only to later find it was 'only' and injector cup - which I may never know for sure if both repairs are done in a 'shotgun' approach to this problem.

[FrankA]

I had the coolant loss at overflow, but it was always happened after going up a steep grade or towing. it would not over heat but it did did move up one tick on the temp gauge. In my case, it was done under warranty on my 2001 (I now have a 2005). Because it was done under warantee they had to trouble shoot it according to GM procedures which meant doing one side and giving it back to me and then doing the other side when the first fix did not work. They did seal the injecter cups, but I don't think they removed the engine. One thing they did do that I wasn't pleased with is they let the air out of the tires so the could reach the engine bay easier. Also, when waiting for parts I went by and found the truck in the back outside with the parts in the back subject to exposure to the elements---not happy! It took over three weeks to complete and at one point they said it would take three weeks just to get parts--after much complaing (I use it for work) they called other dealers and found the parts. I don't use that dealer anymore---I try to do as much of the maintenence myself now. Also I traded my 2001 in on a 2005 at the end of a month to another dealer site unseen!! Actually got a decent deal on it! They knew it would be fixed under warantee, but I think they thought the could get me on the condition I claimed it was in--but becuase it was in great condition I they couldnt complain--I think it is still on the lot--Almost wish I could buy it back--it was a great truck with much more power than my 2005. Good luck with your truck!

[Scott Glewwe]

I have had both problems. The symptom for the injector cup failure was a drop in oil pressure to about 25 psi. Checked the oil for coolant - bingo! (press the dipstick onto a clean paper towel, the coolant will form a lighter colored ring around the oil). The head gasket symptoms are just like what you describe. Puking coolant out the overflow, low coolant, hard upper radiator hose - btw do you have cab heat? I lost that too. Engine temp seldom reached normal. Typical driving symptom would be no cab heat, engine would not warm up. Occasionally the engine temp would spike up to normal followed by the low collant light coming on (and coolant "smell") then temp would drop to 'zero' and stay there. Really made the diagnosis easy for the dealer when I drove into their service area and after I turned off the truck, coolant puked out all over their clean floor.

Could it be that they never ran the engine long enough (fast enough) for enough pressure to build up to push CO2 out the overflow and register on the tester? In my case, the engine had to be driven for awhile (15-20 minutes) before the coolant would get blown out. I think the thermostats have to open before much of the CO2 can get to the radiator and into the overflow tank.

[More Power]

The injector cup seal problem that allows combustion pressure to find its way into the cooling system involves the small end of the cup. That seal is formed by Loc-Tite 272 and clamping pressure. I suppose coolant could find its way onto the piston while the engine is off, but for it to be that bad, it'll be putting a lot of pressure into the cooling system when the engine is running as well.

A cup seal problem that allows coolant to contaminate the engine oil would have to be due a problem with the two synthetic compound o-rings that seal the large upper-end of the cup. This wouldn't be all that likely, but I suppose possible.

Head gaskets usually wind up being at fault for your symptoms, but the recent injector replacement and now cooling system probs may be more than coincidence.

It seems that many of those with a cup seal or head gasket problem see the cooling system build pressure while the engine is idling. This may be because of pilot injection, which is active while idling. Injecting fuel into the combustion chamber at idle well before TDC may cause enough of a pressure spike to cause the cooling system pressure. Just my thoughts...

If you have an engine that produces excessive cooling system pressure at idle, I imagine one could determine which cyls are affected by using a Tech II to selectively disable injectors and watch a pressure gauge to see which cyls build pressure in the cooling system and which don't. This would save the expense of tearing down both cyl banks if the problem involves just one side.

Jim

[Mark Rinker]

Thanks for the input, MP.

I will suggest the 'isolating cylinder' idea to the service techs. To their credit, they have been slow to point their finger at head gaskets, but are also running out of other possible causes at this point.

The Service Manager says it will be about $3800 parts and labor to replace the head gaskets. I am not sure that its worth putting that kind of money into a 170K mile engine. Today I found a Minnesota recycler with an amazing deal - a 2001 LB7 with only 9500 documented and warranteed miles - for $5500. (The low mile Allison is also available for $2500.)

Which makes more sense - $3800 for a repaired, high mile engine - or $9000 total cost to remove and install a nearly new engine? Based on used Duramax prices, the takeout engine could be repaired and sold for at least $3000, bringing my total repower cost to about $6000.

Hmmmm....stay tuned for the next installment of "As the Wrench Turns".

[precision37]

Try replacing the cap on the expansion tank. If that doesn't fix it, it is most likely a head gasket.

[Kennedy]

This has been realtively common among 2001 vehicles. Not epidemic, but it happens. On the plus side, it seems as though it's cured the first time.

Speculation: Tq spec changed? Machining finish specs changed? Who knows.

One thing I will say is that many "veteran" technicians will pull the engine when doing a head job as it's just as fast and you can do a better job when not standing on your head...

[Kennedy]

I've seen one case where a pressurized cooling system was fixed by cup re-seal, and heard of another. The local case was a 2003 model, and I think the other was 2003 also. Most commonly head gaskets on 2001 models.

The local truck did have one injector replaced well prior to the leak though.

More speculation:

Early injectors had a tendency to crack and fill the crankcase. Later ones seemed to erode. It's possible that part of the hold down strategy/TQ spec was altered along the way.

[JohnC]

A 7 year old engine with (only) 9500 miles might not be as good a deal as it seems at first glance...

[Mark Rinker]

It was recently was pulled from the truck and is now palletized/inventoried inside - it hasn't sat outside in a wrecked truck in the snow like boneyards of the past. What would you be concerned about?

[More Power]

I visited the local GMC dealer today, and talked to their lead diesel mechanic about your problem. Here's what I learned.

1- The GM flat rate for a single head gasket replacement is 24 hours, both is 32 hours. Multiply that times what your local dealer gets per hour. Here, replacing both head gaskets would cost $2400 plus incidentals (gaskets, sealants, fluids, etc.). Replacing both head gaskets in a medium-duty truck requires 40 hours.

2- The last LB7 "cooling system overpressure" problem this mechanic dealt with was due to injector cup seals. He said that regardless of what might be the cause, the engine gets new head gaskets and the cups are resealed at a local engine shop that sublets the work. The engine shop does any required head work and pressure tests the heads before returning them to the dealership. This effectively eliminates any call-back problems due to cup seal leaks.

Jim

[Mark Rinker]

Thanks for the information, Jim. Sounds like the engine is coming out of this truck, one way or the other.

[More Power]

When I first heard of cup seal leaks, I wondered by the cups weren't threaded on the small end, so they screwed into the heads. With a little sealant, I believe this would make a much better and more durable seal. If any aftermarket vendors begins manufacturing them, let me know. I'll do a story about the first set! :D

Jim

[Mark Rinker]

I am considering this scenario with the dealership.

1) They redo the injector cup seals (only) on the driver's side - at their expense. I take the truck back, see if the problem is corrected. If not, they do the passenger's side as well. If this solves the problem, they pay the bill as it was a bad seal from the injector warranty work.

2) If problem still exists, we dive into head gaskets, and MRE foots the entire bill.

Does this approach sound reasonable?

[JohnC]

What would you be concerned about?

Are you talkin' to me?


I believe that infrequent use and/or short trips is just about the worst thing you can do to an engine. With 9500 miles, this engine has seen on average about 1500 miles per year. Regardless if it was one 1500 mile trip and 11 1/2 months sitting idle, or two 2 mile trips a day, it can't be good for the engine!

JMO YMMV

[Mark Rinker]

Good point. However, with miles that low its hard for me to be too concerned about the effects of any imaginable scenario - start and stop driving, extended periods of non-use, etc. A good oil change, new fuel filter and tankfuls of fresh fuel with additive should clear up anything that ails it.

[JohnC]

with miles that low its hard for me to be too concerned about the effects of any imaginable scenario - start and stop driving, extended periods of non-use, etc. A good oil change, new fuel filter and tankfuls of fresh fuel with additive should clear up anything that ails it.

Imagine this scenario:

Short trips without reaching and sustaining normal operating temperatures build up acids in the oil. These acids promote corrosion of bearings, hardened (nitrided) surfaces and iron parts. If the oil was changed every 3-400 miles, (couple of times a year), maybe no problem. If it was changed once or twice or never in the 6-7 years, bad news. Also, combustion deposits from low temp operations build up on ring lands and such.

Long periods of no use promotes corrosion damage to cylinder bores, cam lobes, and the like as the oil film migrates off.

In the aircraft world I see engines that get 50 - 100 hours of use every month go 2000 - 2500 hours with nothing more than scheduled maintenance. The ones that fly 50 - 100 hours a year, on the other hand, are lucky to get half that without major repairs, and when overhaul time comes, a lot more major parts get thrown out.

[Mark Rinker]

Okay I get it. There are lots of other options out there. I'll try to find something newer and with more 'average' miles. Thanks.

[JohnC]

Hey! I wasn't meaning to talk you out of it! Maybe it was well cared for and driven regularly. I don't know. If you can't find the maintneance records, you might consider boroscoping a cylinder or two. (Don't know if that's practical given the complexity of the heads...) If they're clean and the oil doesn't look like it was put in in 2002, then it might be a great buy!

Otherwise, it's a pig in a poke...

[rob from bc canada]

Mark

Have you considered going around to see if you can find a whole new(er) truck you like at a dealer someplace?

See what you have to pay to trade up?

By the time you put in the new engine, and get everything working again, and no warranty, and whatever else...

Now, you might not want to go to your local dealer, but all's fair in love and auto sales, they say...

[Mark Rinker]

Truck is back in the shop today. Kenny even gave me a ride home to see how the whole coolant/pressurizing scenario unfolds. When at the dealer, they looked the truck over, and pulled up some new 2007 LMM 3500 SRW trucks in the area.

Options 1) Fix what ails the truck. Write a big check. Continue.
2) Trade up and take the lick in trade difference. Deferred pain.
3) Repower and own the truck for a few more years. Immediate pain - better longterm outlook.

More soon.

[Mark Rinker]

Things I have learned that might save you some time (hopefully you'll never troubleshoot this one).

#1) Testers used at GM dealerships to indicate CO in the overflow tanks do not work properly for diesels. Instead of the blue liquid turning yellow - it slowly turns brown. Not sure what this means, but its a waste of time.

#2) The top radiator hose rigidity doesn't give you any clear indication of the problem. Side by side with my two trucks, both at operating temperature, I couldn't tell the difference in rigidity of either top radiator hose.

#3) If you really want the best visual indication of a pressurization problem - operate the truck to normal operating temperature, and with the engine running (and the truck in P and parking brake set) observe the overflow tank with a flashlight. Shine it on the ridge leading vertically up to the top of the tank from the smaller of the two hoses that attach at the bottom. The smaller hose is the one that leads from the top of the radiator - where bubbles eventually accumulate, before making their final trek to the highest point - the overflow tank.

About once every minute, mine will 'burp' about 3 or 4 marble sized bubbles that make their way to the top of the overflow tank. Looks kinda like one of those old fashioned bubble ornaments on grandma's tree. Now, that I can SEE the problem, I am convinced. :(

[Kennedy]

In a severe case, the system will hold psi and the hose will remain hard overnight.

I'll add that if you have a leak and you run the truck up to normal operating temp with the cap off, then put the cap on you will also build pressure.

[Mark Rinker]

(Note: I have merged three of my related posts having to do with the cooling system pressurization. Hope this combined info will help others in the future...)

Since the weather has warmed up, no coolant loss occurs. The bubbles are still visibile at warm engine idle at the overflow tank, but the coolant level stays visible in the bottle and does not get forced out the overflow tube. Weird! I was losing up to 2 gallons per day when it was cold - plow on, or plow off.

The worst days for this happening were the coldest, in retrospect. I expect there is a logical answer if you understood the coolant flow and the dynamics of the two thermostats opening and closing as cold air flows over the radiator.

I may opt to run up some more miles on this engine before doing the swap, if summer is not going to present a problem. Tomorrow the truck and trailer are hauling 7K# about 250 miles - we'll see if it can hold its water...meanwhile the 'new' Duramax LB7 is on its way to MN from FL.

[DURAMAX HD 2001]

My 2001 would turn the low cool light on every 3 weeks in the beginning. After about 2 months of looking as you have I too found pressure building in the system. I took it to the dealer they replace cups and head gaskets. So far 1 year later all is good.

[Mark Rinker]

Was it done under warranty, or on your dime? Can I ask how much you paid for the repair?

[Philsauto]

Was it done under warranty, or on your dime? Can I ask how much you paid for the repair?

Mark, did you ever get an answer to this? My LB7 pressurizes the cooling system when cold but has no other symptoms. Needless to say, I'm not excited about either doing or paying for head gaskets. Is yours fixed or are you still running it?

[Mark Rinker]

I have run it about 15K miles since it started last winter. Coolant consumption is erratic, but averages about 1 gallon per 500 towing miles.

The truck was sold last week on Ebay 'as-is' with full disclosure of the head gasket problem. The buyer can do the work himself and was happy to find an inexpensive 2001 with extras.

[moondoggie]

Good Day!

Would pressurizing the cooling system with a Stant or similar, with engine off & cold, have helped find this problem, particularly since it seems to be tied to cold ambient temps? I know with my ancient stuff, it has ALWAYS gotten me to the problem, although I've not had an internal leak yet. My understanding is that if a head gasket or such failed, pulling the glow plugs, pressurizing, & waiting would eventually make it clear what was leaking.

Just a tech-type question from one who'd like to know more... I don't even know if a DMax has glow plugs, for that matter. :(

Thanks & Blessings!