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Discussion Starter #1
My 2012 NA AJ133 mysteriously accumulates excessive pressure in the coolant system, and I can’t identify where it could be coming from.

I ask that before leaving a response, please read the full description to make sure that your reply doesn’t disregard things I’ve already done, checked or seen.

Only knowledgeable responses from those that are familiar with the system please. I list a good bit of detail that I hope can paint a useful picture of the situation to experienced wrench-turners and mechanics that know this engine reasonably well, beyond the basics.

That said, any helpful, experienced and knowledgeable ideas are gratefully welcomed. I certainly appreciate any help on this.

Symptoms are:

The problem first presented itself about a year and 10,000 miles ago, by a random misfire failure driving down the highway, after which I took it to the dealership to identify/fix. The dealership didn’t get to look at it for a week, and when they did, they said I needed a new engine – they said they found a tiny amount of coolant in a cylinder, and nothing more. They didn’t have enough time in the evaluation to charge me even an hour.

From there I took it to a reasonably good, experienced European indy mech that had serviced it regularly for a couple years before I owned it. He looked at it, looked into the same cylinder (boroscope) and other cylinders, and said they didn’t see anything to make a diagnosis from, possibly a slight trace of something, maybe fuel. All he saw was a slightly fouled plug. Cleaned it, ran fine.

I put a bottle of Blue Devil through it after that, flushed it out & refilled with fresh coolant, and no more misfires since, cooling system is cooling the engine fine.

Typically after running for 50 or more miles, excessive pressure accumulates in the cooling system and remains after cooling. Top cooling hose expands and remains so until surge tank cap is removed to relieve pressure.

Coolant level lowers by as much as 3 or 4 inches from the FILL line while under pressure, but returns to the line when pressure is relieved because hoses contract to normal size/shape then.

Pressure can get so high that slight amount of coolant might leak from the thermostat bypass port at the front of the coolant pump, but very rare and only after building more pressure than usual from driving far and in hot weather without cracking surge tank cap to relieve pressure at some point.

There is no overheating, no faults. The heater and A/C work perfect. Engine coolant temp is consistently around 185 – 190 degrees F (from OBD).



What I’ve checked:

I have replaced cooling hose from the throttle body to the rear heating pipe, the hose from the engine output pipe to the thermostat, and from the coolant pump to the thermostat. I have replaced the coolant pump and the thermostat. I replaced the FoMoCo surge tank cap (200 kPa (30 PSI)).

None of these changed anything in the mystery pressure accumulation.

Combustion test shows no exhaust/combustion gas in coolant. The coolant stays clean, no oil, and never any coolant in the oil.

I did a leak down test on all cylinders. Bank 1 had a couple cylinders that might have been about 15% loss – within acceptable limits, sound coming from oil filler cap only (no intake/exhaust/coolant leak)

Right bank solid (slight hissing at oil cap as expected). No cylinders produced even a trace of bubbles in the coolant tank (I used 80 PSI for leak down tests).

I’ve emptied/filled the coolant a few times , running the Blue Devil through it, replacing hoses, pump and thermostat, looking for clues, and each time pulled a vacuum on the cooling system, no leaks – solidly maintaining the vacuum after closing the valves for many minutes after turning off air, so there is no leak there. Solid.

Between repeated solid vacuum on the cooling system and god-to-great leak down test on all cylinders, I don’t know where the pressure can be getting into the cooling system from .

I know that coolant expands when it gets hot, but it returns to normal when it cools – in a closed system anyway.

I know that if I let the pressure accumulate without occasional relief, it will probably leak where it can.
 

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Mileage?

Are you using a a vacuum type system to drain and refill the cooling system fluid?

Rob
 

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Discussion Starter #3
Hi Rob.
Current mileage about 138,850 miles.
Yes, I've gotten pretty good at using a very helpful Harbor Freight "Maddox" cooling system test & fill kit that pulls a good vacuum. And I've used it a good 5+ times on this with consistently good results. As I said in the OP, it holds a good vacuum after applying the Blue Devil liquid, then after replacing a couple hoses, pump,& thermostat, and some just-plain-testing. At this point, it takes no time to drain the coolant, swap out a part (I've got the upper & lower rad hoses, & the one that comes off the thermostat and splits-off to the surge tank & heater circuit on the way to me now) and check vacuum then refill, with no air pocket when I button it up.

The only source of pressure entering the system that I could think of is a cylinder by head/gasket leak, but that could only be on compression/power stroke, which would leave combustion gas in the coolant. No sign of that (with leak tester of course).
 

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The swelling of the hose would indicate combustion gasses infiltrating the water jacket someplace, most likely a head gasket but that's just an [educated] guess at this time.

Another guess is that the leak test was performed on a cold motor? You may want to attempt another leak test - especially on the previously identified "weaker cylinders" - with as warm an engine as your mechanic can stand to work on (cue the oven gloves) and see if there's a further denigration of cylinder pressure under test.

Even a simple compression test on a warm motor should work - the results should return in the 190-200 psi with the throttle body butterfly mechanically "jammed" open during cranking (remember it's an electronic fbw-type throttle so pressing on the gas pedal during cranking won't help).

If you drive the car with the expansion tank cap removed, does the coolant overflow when the motor is warm?

Rob
 

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The surge tank / radiator cap should vent any excess pressure over its rating. If it's not then maybe the blue devil plugged the vent system in the cap. If you were getting excessive pressure in the cooling system the vent on the cap bleeding all over the surge tank. If it's not missing or getting rid of coolant could just be a weak radiator hose. My 2 cents.
 

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I had similar symptoms on my 2010 at around 130,000 miles. Tried the blue devil. It held for a couple of weeks. Clean oil, clean coolant and a lot of pressure in the system. Misfires. Turned out to be a head gasket. My Indy sent out the affected head as it had a slight warp. All was good after that. Ended up selling it to upgrade to an l405. She had 146k on her at that point. Running like a champ.
 

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Discussion Starter #7
The swelling of the hose would indicate combustion gasses infiltrating the water jacket someplace, most likely a head gasket but that's just an [educated] guess at this time.
That's the prime (if not only) thing I expected to find. But the odd thing is that I've tested for combustion gas in the coolant a few times, and nothing. It doesn't show any sign of bubbles coming up in the coolant at any time check either, but it is getting in there from somewhere

Another guess is that the leak test was performed on a cold motor? You may want to attempt another leak test - especially on the previously identified "weaker cylinders" - with as warm an engine as your mechanic can stand to work on (cue the oven gloves) and see if there's a further denigration of cylinder pressure under test.
I did let it cool a bit when I did the leak down test, but from what I've read, the rings seal better when it's hot. Testing a cool engine calls for a couple squirts of oil in the cylinder from what I've read.
When I get a little time, I'll get it hot & do another leak down test.

If you drive the car with the expansion tank cap removed, does the coolant overflow when the motor is warm?
I'd assume it does, I'll have to try it. My wife's got the same engine, same year, no problems at all and cooling system that does not build pressure beyond expected. But if I crack the cap when it's hot, coolant comes out.

Thanks for the helpful educated pointer
 

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Discussion Starter #8
I had similar symptoms on my 2010 at around 130,000 miles. Tried the blue devil. It held for a couple of weeks. Clean oil, clean coolant and a lot of pressure in the system. Misfires. Turned out to be a head gasket. My Indy sent out the affected head as it had a slight warp. All was good after that. Ended up selling it to upgrade to an l405. She had 146k on her at that point. Running like a champ.
That's exactly what I'm expecting and have been trying to identify. I asked the indy to check for that, but he's looked at it and said it doesn't look like one at this point.

BUT it does take a while for it to build-up the pressure, and only after extended highway speeds, so very early in the stage?
I'm fine with getting the heads pulled, checked, and built back up and maybe the timing chain guides along the way. It's otherwise a sweet RR,and I'll keep it for longer than I should anyway.
 

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Discussion Starter #9
The surge tank / radiator cap should vent any excess pressure over its rating. If it's not then maybe the blue devil plugged the vent system in the cap. If you were getting excessive pressure in the cooling system the vent on the cap bleeding all over the surge tank. If it's not missing or getting rid of coolant could just be a weak radiator hose. My 2 cents.
I tested my old cap, and it opens @ 30 PSI. I went ahead & replaced it (I never try to save a buck on coolant system maintenance) and it performs the same.
The Blue Devil isn't a typical sealer that clogs up the system. It's all liquid, no copper or fibers or chunks. Thermally activated, and once it reaches the reactive temp, it's done. Only good for the first heat cycle, and after that, inert. I was surprised how clean and after applying it, it all gets flushed out and leaves no trace.
But I guess with a 30 PSI cap, it takes more than most to vent. And there's no sign of coolant blowing out. No loss of coolant, and hasn't misfired since putting the BD through it.

Which is why I have ordered a new set of hoses last weekend that I should get tomorrow.
I don't know if these are original hoses (131k miles & 8 years), but I wonder if the top hose is weak and expanding and somehow causing the excess pressure. But if so, it still has to come from somewhere. And if it were just weak hose(s), I'd expect it to contract back once cool.

...Which is why I first suspected something strange like loose head bolt(s), warped head(s) that only leaks when hot & under the highest pressure. But neither I or the mechanic got positive results when testing for combustion gases in the coolant system.
 

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That's exactly what I'm expecting and have been trying to identify. I asked the indy to check for that, but he's looked at it and said it doesn't look like one at this point.

BUT it does take a while for it to build-up the pressure, and only after extended highway speeds, so very early in the stage?
I'm fine with getting the heads pulled, checked, and built back up and maybe the timing chain guides along the way. It's otherwise a sweet RR,and I'll keep it for longer than I should anyway.
Yes, while he was doing the heads o had the guides done as well. Sorry I have no further input for you. Best of luck!
 

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Discussion Starter #11
I have no further input for you. Best of luck!
Well I appreciate your help with letting me know about your experience with the same problem. It probably is the same root cause, but still missing some basic head gasket indicators.
 

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Discussion Starter #12 (Edited)
If you drive the car with the expansion tank cap removed, does the coolant overflow when the motor is warm?
I'm not comfortable with driving around without the cap on, but I did run it for about an hour today without the cap on. Mostly at idle, but a few times, I let the engine run up around 2500 RPM for about 3 minutes at a time.
No sign of bubbles coming up through the coolant, and no overflow.
I did have my combustion gas tester on top of the surge tank most of the time, but that doesn't contain air/coolant pressure within the system at all.
The coolant level in the surge tank did slowly raise-up about 3 inches from the cold fill line as it warmed-up and it stayed at that same level, and it was running (OBD reading) steady between 188 - 190 F once it got to temperature.
After I shut it off, the coolant level slowly returned to the same level it was before running it, as it cooled to ambient.

Every time I'm ready to take it in & have them just go ahead & replace head gaskets, there's always something else that just doesn't make sense.
I've never heard of a blown head gasket or a head warped that doesn't present more of a cooling problem.
 

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Discussion Starter #14
I'm in denial of what AnvilRob is probably sure of - a head problem of some sort.
I did get the new hose set (upper rad hose LR011360, lower hose LR011482 and other lower LR011480) on the other day, which I don't expect to help other than knowing that my hoses are all new and strong now. (I've recently replaced the pump, thermostat and 2 short hoses that attach to those, and the hose that runs between the thermostat & rear swirl pot cross-over pipe.)
I also replaced the 30 PSI coolant tank cap with a 16 PSI one.
Haven't driven at highway speeds for extended periods since then, but once I do, I'll be able to tell if it keeps the pressure from building as high.

After fitting the new hoses & getting ready to refill with coolant, when I pulled the vacuum on the system, AGAIN I let it sit at the lowest vacuum it would reach (-25 on the gauge of -30) for a while, 10 minutes or so, and the needle didn't move enough during that time to notice. Granted, the engine was not hot, but I just can't see how any leak, head or otherwise could be so absent until it gets to highway speed for a while. I did consider that maybe the one cylinder that is leaking could possibly be at TDC, but still, odd.

So I filled it with coolant again, burped it (that's so easy now after so much practice) and ran it with the OBD reader to make sure that the ECT is again, healthy as always - 188 - 190.

It's still a mystery to me, but I know that I should do likeI'm guessing AnvilRob thought - get the heads checked and replace head gaskets.

But as long as it's perfectly healthy other than the coolant system pressure going up and staying up even after it cools, and if the 16 PSI cap can help control that, I'll keep driving it until a can see any- ANY other sign of something wrong.
 

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Dumb question from a less experienced person than some people in this thread, but...

What (exactly) is your coolant temperature during a typical drive cycle? Can you check with an OBD-II tool?

I have heard that the threshold for the L322 (‘10-‘12 at least) showing anything other than exact middle is “already too late”.


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Ok. I have a rediculous amount of experience with these engines and the problem you are talking about. You have coolant getting into the cylinder via the headgasket. The design allows coolant to seep through and exhaust gas to go into the cylinder. It's a very tight tolerance and multiple different things can cause it to seep or leak. The dealer even told you exactly what it needs. Stop wasting your time and money and do the headgaskets. If you want confirmation, buy a bore scope and check for yourself.

Get the vehicle warm, then put a pressure tester on the cooling system. Pressurize to atleast 20psi. Then remove all spark plugs, or the spark plug where the misfire occurs, insert camera and observe.

Compare what you see to a known good cylinder on another bank. It should look dry and have carbon build up. If it's clean, or damp it is an indication that water is entering the cylinder and steam cleaning the cylinder. If it's bad enough you'll see a puddle.
 

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Discussion Starter #17
What (exactly) is your coolant temperature during a typical drive cycle? Can you check with an OBD-II tool?
Yes you can. One of the OBD readings is ECT - engine coolant temperature.
The 2010 - 2012 coolant system is designed to quickly get to operating temp. The multi-stage thermostat begins to open at about 190 F, and is fully open at 216 F. Mine operates at 185 F to 190 F, and that's under load on days around 100 F ambient.

I have heard that the threshold for the L322 (‘10-‘12 at least) showing anything other than exact middle is “already too late”.
The needle is the equivalent of the old "idiot light". It stays in the middle & doesn't show minor variances. If it ever does get above middle, you need to pull over immediately & shut it down, or the heads & maybe block will quite possibly be damaged.

I'd say it's too late SOON AFTER it goes above the middle, as in 3 minutes or so. But some may consider that too conservative.
 

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Wrench monger is dead on. (P38 owner)
Stop buying parts as stated. This is a textbook example of head gasket failure. It was obvious at your first post, and confirmed in your following updates. A few points why your testing isn't screaming head gasket to you.

1 Cylinder has way more pressure from piston than a vac test (-25, vac vs pressure doesn't matter) A coolant vac/pressure test is designed primarily to check cooling systems @ cap relief pressures, not head gaskets.

2 The HC testers with liquid will not determine small head gasket leaks. They are not precise enough for small leaks. The heads may not leak enough at cooler temps and it's hard to test with cap off and get it up to operating temp without it boiling over, as there is no longer a pressure sealed system to keep boiling temps down. High end HC testers test in PPM and can detect much better. The engine can idle all day long and not show HC's. But put a load on it, and that's a different story. (highway speeds)

3 When they looked at the cylinders with a borescope they should have determined head gasket right away, as the cylinder would be washed/steam cleaned and obvious.

4 You have a very small leak. The leak is small enough that the cooling system is maintaining temps, but the coolant system is pressurizing from the leaking HG.

5 Fuel doesn't pool in a cylinder unless you have a leaking injector, which does not cause cooling system pressures to rise. The dealer found coolant in the cylinder. There should never be coolant in a cylinder.

6 Head bolts don't loosen after 138K

7 A compression test warm with the coolant cap off would have been better than leak down test. But a small HG leak might be too small to see the difference at the gauge. But you might see weird pressure jumps on the cooling system if you also had a pressure gauge on the coolant system while doing a compression check.

Sorry this is so long, but others have stated head gasket issue, but now this may help to understand how we came to that conclusion based on your posts. You gave us all the info we needed with all of your steps. There is only 2 things that generate pressures in water cooled petrol engines. Heat (causes coolant to expand), and pistons on the compression stroke.
It might not be what you wanted to hear, but on the bright side you don't need a new engine. No coolant in the oil saved the bearings. You now have a totally new reliable cooling system. Just make sure you go back to the original spec reservoir cap (30 psi).
I lost a lot of hair, going thru what your are going thru, on my P38. Ask any P38 owner about this, they would see this a mile away. I saved mine, but most never come back if overheated mostly from dropped cylinders, which is not an issue on a L322. Now at least I know one other person other than myself, that can drain and strip an entire Land Rover cooling system 3 times a day for a week going crazy with no results. I think I am now a major share holder in Prestone. Hang in there Mark.
Mark
 

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Wrench monger is dead on. (P38 owner)
Stop buying parts as stated. This is a textbook example of head gasket failure. It was obvious at your first post, and confirmed in your following updates. A few points why your testing isn't screaming head gasket to you.

1 Cylinder has way more pressure from piston than a vac test (-25, vac vs pressure doesn't matter) A coolant vac/pressure test is designed primarily to check cooling systems @ cap relief pressures, not head gaskets.

2 The HC testers with liquid will not determine small head gasket leaks. They are not precise enough for small leaks. The heads may not leak enough at cooler temps and it's hard to test with cap off and get it up to operating temp without it boiling over, as there is no longer a pressure sealed system to keep boiling temps down. High end HC testers test in PPM and can detect much better. The engine can idle all day long and not show HC's. But put a load on it, and that's a different story. (highway speeds)

3 When they looked at the cylinders with a borescope they should have determined head gasket right away, as the cylinder would be washed/steam cleaned and obvious.

4 You have a very small leak. The leak is small enough that the cooling system is maintaining temps, but the coolant system is pressurizing from the leaking HG.

5 Fuel doesn't pool in a cylinder unless you have a leaking injector, which does not cause cooling system pressures to rise. The dealer found coolant in the cylinder. There should never be coolant in a cylinder.

6 Head bolts don't loosen after 138K

7 A compression test warm with the coolant cap off would have been better than leak down test. But a small HG leak might be too small to see the difference at the gauge. But you might see weird pressure jumps on the cooling system if you also had a pressure gauge on the coolant system while doing a compression check.

Sorry this is so long, but others have stated head gasket issue, but now this may help to understand how we came to that conclusion based on your posts. You gave us all the info we needed with all of your steps. There is only 2 things that generate pressures in water cooled petrol engines. Heat (causes coolant to expand), and pistons on the compression stroke.
It might not be what you wanted to hear, but on the bright side you don't need a new engine. No coolant in the oil saved the bearings. You now have a totally new reliable cooling system. Just make sure you go back to the original spec reservoir cap (30 psi).
I lost a lot of hair, going thru what your are going thru, on my P38. Ask any P38 owner about this, they would see this a mile away. I saved mine, but most never come back if overheated mostly from dropped cylinders, which is not an issue on a L322. Now at least I know one other person other than myself, that can drain and strip an entire Land Rover cooling system 3 times a day for a week going crazy with no results. I think I am now a major share holder in Prestone. Hang in there Mark.
Mark
Thanks for backing me up on this. Also I'm not just a p38 owner, I also work on these trucks for a living. Lol
 

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Thanks for backing me up on this. Also I'm not just a p38 owner, I also work on these trucks for a living. Lol
With that experience...do you recommend any "upgraded" parts to diminish the chance of yet another hg failure (like better head bolts/studs, different head gaskets perhaps)? The OP has an N/A 5.0L, so is it correct to assume that supercharged engines are even more prone to the failure due to the increased pressure in the combustion chamber?
 
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