: Is it stupid to put in a new engine?????



Free Tibet
03-04-04, 02:41 PM
I have a '99 DeVille with problems: leaking head gaskets and pistons rings in #6 and #8 are not sealing. I've already put in a new heater core, radiator, and various hoese. Also a water pump.
Now I am deciding whether or not to replace my Northstar engine with a Jasper Long Block. What else would you replace if doing the new engine? I'm not sure what you don't get with the long block. I want to replace whatever else can go bad at this time. Or is this all just a very bad idea??

zonie77
03-04-04, 03:14 PM
I havn't looked at Jasper long block but an engine swap is about the same amount of work as the headgaskets.
The long block is usually block, heads,cams. Usually the oil pan ,cam covers aren't included but that varies.

Free Tibet
03-04-04, 04:11 PM
It's not just head gaskets. The rings on pistons 5,6,7,and 8 arn't sealing. Between both jobs I'm told a new engine is less money. What I'm wondering, while the engine is out, what else can opr should be replaced. THe car has 87,000 but I would want to get 87,000 more if I put in a new engine.

Lawrence
03-04-04, 04:57 PM
I would get another opinion. How could the rings be checked with blown head gaskets? The rings, if not sealing properly, are likely just carboned up and can be cleaned without disassembling the motor past the head gaskets.

Is this motor already apart? If not procede with the head gasket repair and wait until you see the bores before makng a decision to replace the motor. You'll likely find there is no real problem with the rings. You should get 87K more from that engine.

Unless you just flat have a lot of money lying around you'd like to part with. Then replacing it is the simplest way.

Free Tibet
03-04-04, 05:25 PM
He performed a "leakdown" test. THis is the test, mentioned elsewhere on the forum, where you remove the plugs and pressurize each cyluybder with air. He aslo did other tests. He also believes the cooling system to combusttion chamber is breached and both head gaskets are leaking. The Cadillac dealer was less specific but just as gloomy about any chance for getting away with only new head gaskets. The current mechanic seems like the real thing in engine rebuilds.

Free Tibet
03-04-04, 05:33 PM
By the way, this is the second time the front head gasket failed. Also the injectors at #4 and #6 were replaced on another occasion. What would cause all these failures in the cooling system??

Lawrence
03-04-04, 06:04 PM
All I could say is, bad workmanship. It should not have happened again. Did the same place do it the first time as has it now? If so it's just another good reason to get it somewhere else for a second look.

I am still a little confused about the piston ring diagnosis. That would be about impossible to tell with a leak down test and blown head gaskets. Assuming he is diagnosing the bad rings by adding oil to the test cyl., if you add oil to the cylinder and the compression comes up, that usually that indicates a sticky OR worn ring. No way to tell which. As I said earlier, very unlikely they are broken or worn out.

But on this engine a leak down test (with oil) can falsely indicate a ring leak when it is really a head gasket as the oil will help seal the head gasket as well, if just a little too much oil is used. Leak down tests are not conclusive in themselves.

I would say, as above, proced with the head gasket repair and go from there.

Good Luck!

dloch
03-04-04, 06:46 PM
I am still a little confused about the piston ring diagnosis. That would be about impossible to tell with a leak down test and blown head gaskets. Assuming he is diagnosing the bad rings by adding oil to the test cyl., if you add oil to the cylinder and the compression comes up, that usually that indicates a sticky OR worn ring. No way to tell which. As I said earlier, very unlikely they are broken or worn out.

But on this engine a leak down test (with oil) can falsely indicate a ring leak when it is really a head gasket as the oil will help seal the head gasket as well, if just a little too much oil is used. Leak down tests are not conclusive in themselves.

Good Luck!I agree, you can't do a leak down on a motor with a leaking or blown head gaskets and get any conclusive evidence that the rings are leaking or not sealing.

If this is the second time on the head gaskets it's probably pretty safe to assume they didn't timesert on the first occasion. I would certainly not take the car back to the same place for second shot at it trying to get it right especially if they aren't going to timesert this time around.

zonie77
03-04-04, 10:25 PM
My earlier comment was just about the amount of work involved. Doing the heads is about the time of swapping everything over, a little more if you include timeserting.

If a shop is doing all the work I'd tend to go with the rebuilt engine. You added the info about the heads being done prev. Were timeserts done on all the threads?

I also agree with the comments about the hard diagnosis on the rings. There is the known problem with rings sticking...hmmmmmmmm.

BeelzeBob
03-05-04, 01:07 PM
I think we talked about this on the phone...????


The rings are fine. You cannot tell the rings are bad from a leak down test like that. Neither can you tell which cylinder head gaskets are potentially leaking.

Have them do the individual cylinder pressurization test as previously described. Forget the stupid leak down test. Pressurize the cylinder to 125 PSI and watch the cooling system for bubbling as each cylinder is pressurized to see if it is a head gasket and which head gasket/cylinders it is. This is the only conclusive way to tell.

If you are seriously contemplating a new engine I would get a GM engine that is an all new assembly, not a Jasper re-manufactured engine.

formulacarracerjim
03-08-04, 10:49 AM
Hi guys, I am Jim, "FreeTibets tech".

Just curious and not trying to be a smarta** but if I blow somewhat less than 125 psi into the cylinder at top dead center and it BLOWS out thru the oil filler cap opening, (It also LIGHTLY bubbles into the cooling system.) Do you guys really think I should just do the time-serts and head gaskets? BTW I was not the tech that did a previous repairs. Not a full set of time-serts. I just got in on this car. This is a fair amount of this gentlemans money to risk on just the heads. Where is the flow path that is allowing air to enter the crankcase? Lets all work together to present a proper diagnois for this car. I will be glad to just time-sert and replace head gaskets if that is the consensus. (with full warranty on the head gasket work only!) Jim :)

BeelzeBob
03-08-04, 12:38 PM
Hi guys, I am Jim, "FreeTibets tech".

Just curious and not trying to be a smarta** but if I blow somewhat less than 125 psi into the cylinder at top dead center and it BLOWS out thru the oil filler cap opening, (It also LIGHTLY bubbles into the cooling system.) Do you guys really think I should just do the time-serts and head gaskets? BTW I was not the tech that did a previous repairs. Not a full set of time-serts. I just got in on this car. This is a fair amount of this gentlemans money to risk on just the heads. Where is the flow path that is allowing air to enter the crankcase? Lets all work together to present a proper diagnois for this car. I will be glad to just time-sert and replace head gaskets if that is the consensus. (with full warranty on the head gasket work only!) Jim :)

I don't think anyone can answer your question conclusively without pulling the head and seeing what that cylinder looks like. The presumption that air pressure is leaking past the rings...but Northstar engines have little or no history of ring problems like you are supposing . Plus, the owner had no ring related complaints such as smoking or oil consumption....just the coolant loss issue. I still think it is a safe bet to replace the head gasket on the side that shows airpressure leakage into the cooling system ... especially since it is the same side that was repaired (questionably) once before. When the head is off ,which it needs to come off regardless, further accessment of that specific cylinder can be done.

The engine has over 90K on it so expecting a "perfect" cylinder and ring seal is really unrealistic. To make it like new would require pulling the piston out for re-ringing/cleaning assuming that the cylinder bore hasn't been damaged due to coolant intrusion or something. With repeated operation with known coolant intrusion into that cylinder it is possible that the cylinder hydrostatically locked partially on coolant at some point in time and damaged a piston or cracked a cylinder wall. It is also possible that if the head gasket seal is sufficiently bad the air pressure induced into the combustion chamber may be leaking thru the gasket to the adjacent oil drain back hole....i.e..the crankcase...which would be completely independent of the rings.

If further diagnosis is really needed to make the decision (I do not think that there is sufficient info available to do more than guess at this point) then I would recommend a compression test of all cylinders to see where that cylinder lies. A compression test, due to the brief nature of the compression event, will possibly give a better picture of the actual health of the rings...i.e..if the cylinder still has good compression then I would not go after any ring sealing issues and certainly would not expect a ring problem of any mangnitude. A compression check might be inconclusive because, even if it is low in that cylinder, it still could be because of the head gasket.....so you are back to pulling the head to look.

The other diagnosis that might shed some light is to repressurize the combustion chamber and rotate the engine back and forth to access the perceived leakage past the rings as the piston is at different spots in the bore. Possibly the leakage is only evident near TDC indicating a potential crack in the cylinder liner near the top that could be due to a hydrostatic lock previously...or it could have been there for some time and is partially manifesting itself as the head gasket coolant intrusion issue. Once again, though, taking the head off will be needed to confirm.

Do you have access to a borescope to look inside the combustion chamber to inspect the cylinder walls for grooves/wear patterns/witness marks?? If, for instance, a wrist pin has failed or a pin retaining clip has come out the pin will make vertical marks in the bore that could cause leakage past the rings like described. This would provide a clue as to whether the engine would need to come out or not...

Lawrence
03-08-04, 12:42 PM
You'll be able to tell when you get the heads off. But the pressure could be entering any of the three oil drains in the head, or the oil feeds (one in each head). Remember these aren't your typical "blown" head gaskets. The head is likely loose. Some pressure loss around the rings is normal too, at 125 PSI. A leak down test uses much less pressure. And it could also be the rings are sticking, which these motors are known for. But a cleaning would cure that. The head off would be a great time to clean the affected cylinders. I would cover the piston with SeaFoam and let it soak, then work the cylinder and and piston (rock it around with your hand) and let it soak some more. Finally suck the crap out, work it some more and retest. You can make a plate with an access hole (spark plug). Bolt it down and you'll have an accurate test that will isolate the rings.

When you get the head off you will know. I would leave it "open" with your customer.

zonie77
03-08-04, 08:39 PM
It sounds like the best thing would be to pull the head and see what condition the cylinder wall is in. Other than that you cannot be sure what's going on with this engine.

I'd bet all the change in my pocket that the wall is OK.

brad3378
03-09-04, 12:32 AM
I agree - I think the cylinder wall is okay. My 98 Deville has 130,000+ miles and you can still see the crosshatch pattern from the cylinder hone in every cylinder!

In Mechanic School they taught us to do a wet & a dry compression test.
If the cylinders leak dry, then we squirt a little bit of oil in the cylinder and retest - the theory is that the oil will help the rings seal a little better and boost the compression.

I believe that when the gasket is removed you'll see a leakage through or around the "fire ring" into an oil passage in the headgasket.

Let us know how it turns out - I'm curious.