If the engine turns over when the heads are off it sounds like a hydraulic issue to me. Check to make Sure the head gaskets are good and you did not have a hydraulic lock due to coolant. Other than that Continue to check to see if the rotating assembly has another issue.
Lockup after headgasket replacement
Hey everyone,
I'm working on a 2014 CTS-V. Quick note, I am a certified tech who has plenty of experience with head gasket replacement. I will admit I don't have much experience with heavy mods like this one, but I don't think the mods are related to the issue. Car comes in needing head gaskets replaced. I got everything apart and sent the heads off for inspection, they were fine. Had them cleaned up, then put on new gaskets, torqued to spec, and reassembled everything. On first attempt to start, got a thud. No rotation, not even a little bit, just a thud. I went to the crank pulley and I could rotate it in the opposite direction with expected resistance and intake/exhaust noises until I got to another point of solid resistance. I can go back and forth about 3/4 rotation of the crank until I hit that wall. I've removed one of the heads completely and took out the rockers and pushrods on the other, no change. Put my borescope in each intake and exhaust passage and in every spark plug hold to see the chamber, nothing unexpected. Never seen anything like it before.
Any thoughts?
I'm working on a 2014 CTS-V. Quick note, I am a certified tech who has plenty of experience with head gasket replacement. I will admit I don't have much experience with heavy mods like this one, but I don't think the mods are related to the issue. Car comes in needing head gaskets replaced. I got everything apart and sent the heads off for inspection, they were fine. Had them cleaned up, then put on new gaskets, torqued to spec, and reassembled everything. On first attempt to start, got a thud. No rotation, not even a little bit, just a thud. I went to the crank pulley and I could rotate it in the opposite direction with expected resistance and intake/exhaust noises until I got to another point of solid resistance. I can go back and forth about 3/4 rotation of the crank until I hit that wall. I've removed one of the heads completely and took out the rockers and pushrods on the other, no change. Put my borescope in each intake and exhaust passage and in every spark plug hold to see the chamber, nothing unexpected. Never seen anything like it before.
Any thoughts?
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Pull the other head or at least the PLUGS from it. Borescope the cylinders. Whether you see the cause in there or not, doesn't change the fact that you need to pull the other head.
Why did it come in needing head gaskets? Running on E85? There may be bottom end damage related to the gasket-fail-event.
Why did it come in needing head gaskets? Running on E85? There may be bottom end damage related to the gasket-fail-event.
Since it's a used engine hard to say if the heads were previously surfaced. How much total material was removed from the surface? Pistons at top dead center might be experiencing a clearance issue? I'm not an engine builder, just a thought, push rod length might be an issue too?
A "thud" means something is hitting, naturally. If externally there is nothing binding, and no obvious valve spring or pushrod interference, I'd suspect valve interference - either a damaged spring, or stuck lifter, etc. Take it to the "thud" and look for piston to valve contact.
What brought you to replace the head gasket? That should lead you to the actual problem...?
What brought you to replace the head gasket? That should lead you to the actual problem...?
Was any diagnostic done before pulling it apart?
You know, like cranking it over?
Did it turn over at that time?
You know, like cranking it over?
Did it turn over at that time?
Thank you for the responses! Here is some more information: Car drove in. Running poor with some coolant consumption (not a lot) and external leakage, but still running and driveable. Removing the valve covers originally showed that some of the head studs/nuts were loose. No locktite on them and again this thing is modded so lots of abuse. The gaskets themselves were in good shape except for some of the coolant passage holes showed burns at one cylinder entrance and out externally at another hole. Rather obvious the loose head hardware was the cause.
Is there an efficient way to check the bottom end without heavy tear down or removing the engine from the car?
@MrSurly I did pull the plugs and borescope, said that. I removed all the rockers to eliminate valve interference from the equation. No E85, but does have Meth. The customer drove the car in. Initial complaint was rough running, coolant leak, no codes.
@kittyboy The machine shop said the heads were perfectly true and did not need any resurfacing. Since it drove in, I have no concerns about rod issues...
@random84 I've eliminated the valvetrain at this point. The problem must be bottom end but I genuinely don't know what could have happened, the job was cut and dry from start to finish and it drove in.
@Sudderth I agree I think it's in the rotating assembly but am baffled at how something could happen there. Do you know a way something could get down there during head replacement, I'm not seeing any passages with wide enough access to the bottom end for bolts to fall in to, nonetheless get my borescope in to. I'm also not trying to pull this engine out of the car to drop the pan.
Is there an efficient way to check the bottom end without heavy tear down or removing the engine from the car?
@MrSurly I did pull the plugs and borescope, said that. I removed all the rockers to eliminate valve interference from the equation. No E85, but does have Meth. The customer drove the car in. Initial complaint was rough running, coolant leak, no codes.
@kittyboy The machine shop said the heads were perfectly true and did not need any resurfacing. Since it drove in, I have no concerns about rod issues...
@random84 I've eliminated the valvetrain at this point. The problem must be bottom end but I genuinely don't know what could have happened, the job was cut and dry from start to finish and it drove in.
@Sudderth I agree I think it's in the rotating assembly but am baffled at how something could happen there. Do you know a way something could get down there during head replacement, I'm not seeing any passages with wide enough access to the bottom end for bolts to fall in to, nonetheless get my borescope in to. I'm also not trying to pull this engine out of the car to drop the pan.
If it's a Manual, put it in Neutral.
If NOT, unbolt the converter
Roll the belt off of the AC compressor.
If NOT, unbolt the converter
Roll the belt off of the AC compressor.
Head studs/washers/nuts are aftermarket as the factory heads are clamped down with TTY bolts. The studs are NOT supposed to be secured with Loctite! In fact, they aren't even supposed to be torqued (studs).Thank you for the responses! Here is some more information: Car drove in. Running poor with some coolant consumption (not a lot) and external leakage, but still running and driveable. Removing the valve covers originally showed that some of the head studs/nuts were loose. No locktite on them and again this thing is modded so lots of abuse. The gaskets themselves were in good shape except for some of the coolant passage holes showed burns at one cylinder entrance and out externally at another hole. Rather obvious the loose head hardware was the cause.
These instructions will be helpful when you reassemble the heads to the shortblock.
LSA Head Stud Installation (ARP)
EDIT; I read that you already installed the heads, my bad
.
I don't blame you with regard to pan removal! However, if you do go down that road I've attached an image.Thank you for the responses! Here is some more information: Car drove in. Running poor with some coolant consumption (not a lot) and external leakage, but still running and driveable. Removing the valve covers originally showed that some of the head studs/nuts were loose. No locktite on them and again this thing is modded so lots of abuse. The gaskets themselves were in good shape except for some of the coolant passage holes showed burns at one cylinder entrance and out externally at another hole. Rather obvious the loose head hardware was the cause.
Is there an efficient way to check the bottom end without heavy tear down or removing the engine from the car?
@MrSurly I did pull the plugs and borescope, said that. I removed all the rockers to eliminate valve interference from the equation. No E85, but does have Meth. The customer drove the car in. Initial complaint was rough running, coolant leak, no codes.
@kittyboy The machine shop said the heads were perfectly true and did not need any resurfacing. Since it drove in, I have no concerns about rod issues...
@random84 I've eliminated the valvetrain at this point. The problem must be bottom end but I genuinely don't know what could have happened, the job was cut and dry from start to finish and it drove in.
@Sudderth I agree I think it's in the rotating assembly but am baffled at how something could happen there. Do you know a way something could get down there during head replacement, I'm not seeing any passages with wide enough access to the bottom end for bolts to fall in to, nonetheless get my borescope in to. I'm also not trying to pull this engine out of the car to drop the pan.
•remove the lower #2 each engine mount bolts.
•back out #6 each cradle bolts (leaving some thread engagement).
•mount lift fixture to heads, raise engine approx 1"
There are additional steps of course, but this should provide enough clearance to remove the pan.
Good luck, keep us posted!
FOUND IT!!!
There was a lifter seized at bottom position. When the cam lobe came around to it, wouldn't move. How it happened, I'll never know but it's resolved now!
Thanks everyone for your help!!
There was a lifter seized at bottom position. When the cam lobe came around to it, wouldn't move. How it happened, I'll never know but it's resolved now!
Thanks everyone for your help!!
That lifter bore could be trashed and the cam lobe could be damaged as wellFOUND IT!!!
There was a lifter seized at bottom position. When the cam lobe came around to it, wouldn't move. How it happened, I'll never know but it's resolved now!
Thanks everyone for your help!!
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