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Cadillac Repair/HT4100 Knock at idle
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Question
Hello,
I have an 84 El Dorado with the HT4100 engine. This engine has now developed a loud top end knock that we can't identify. The engine starts easily and seems to actually run fine, however the knock is too loud to actually use the vehicle. Oil pressure doesn't seem affected and the noise is not consistent. It is always there but sometimes varies from a knock to more of a squeel or back and forth. I am starting to wonder if this could be a cam bearing, or if something simpler could possibly be at play. I appreciate the help.
Thank you,
Reese
Hello,
Anyone that has had the ht 4100 is usually familiar with the knock. Either the engine knocked or if you were real fortunate like me with my 88 Allante, it did not knock, but my 84 Eldo did. These engines were common to knock right off the showroom floor.
I have been told it is wrist pins, but these engines ran fine with the knock. Even if you change cam bearings, rod bearings, it is not going away. We used to say it was built in from the factory.
Even if you replaced with a brand new GM target master $5,000 later, you might stil have a engine that may have a knock and then you would be real upset!
This engine came out (all aluminum) in 1982.
They used it until 1989 or 1990 when they changed to the 4.5, the in 1992 they went to the 4.9 and in 1993 the northstar.
The 4.5 and 4.9 rattled to but not like the 4100.
I realize you might not be satisfied with my answer because it is a Cadillac. Cadillac made crappy engines for years.
If you go to a caddy dealer and find a tech that has been around 20 years, ask him about the quality of the ht 4100.
It shouldn't blow up on you, but the sound can drive you nuts.
I have owned over 20 Caddys and many with the 4100.
I now own a Chevy truck with a 454.
Good luck!
Http://www.autotheftexpert.com
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Rob Painter
Expertise
Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?
Experience
Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.
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