Ok, here we go...
I have an 85 Eldorado Touring Coupe with the HT4100 with 67K miles on it. my problem is this....After the car warms up, generally within 5-6 miles I hear a noise coming from the engine bay, now it's not really a knock per se, it's more like a tinny hollow poppingh sound. I doesn't do it while in Neutral and doesn't affect the performance of the car. I am losing no fluids or burning any, but this noise is annoying. I was told it could be the exhaust but it seems to be coming from within the engine. I can't pinpoint it. Could this be the result of the rocker arms breaking as I have heard is common with Eldorado HT4100 engines or should I be hunting for something more technical? I know the cooling system is very fragile on these engines and went through that aspect of the engine, I.E. new intake manifold gasket, new radiator, new water pump and also made sure they put the tabs in when I had a flush and fill done. I'm at a loss as to what it could be. As I mentioned in another post I do have a complete and running 79 Eldorado, but I don't wanna take on the project of swapping the engines out if I don't have too.



Thanks in advance.

Steve

 

Hard to diagnose without hearing it, but this engine has a reputation of a hollow knock warm, worse with A/C compressor on. Cause is too much clearance on the front crankshaft bearings. The aluminum engine will alow you to hear it unlike a cast iron block. Try this, change the oil with a multigrade rated for a diesel car. 15/40 or the like. I use DELO in my 84 Eldo. Insulates better and also has more zinc in it to protect the camshaft. If it is this knock, it will run forever but be noisy.

 

Kyewl, thanks, I'll try that this weekend and let ya know how it goes


Steve

 

Also for future reference put your year and type of Cad in your signature profile. Keeps us from having to remember the type of car you own and you from having to always type it in to the body of your next thread.

 

My Ladyfriends son has a garage/shop; and he listened to it and told me he would guarantee it';s a wristpin. Will thicker oil make this annoyance disappear? or at least fade it long enough for me to sell it?

Steve

 

Wrist pin is unusal but very repairable. With the low miles it may be carbon build up. I would try to decarbon engine before disecting engine. Removing oil pan is a chore to verify which piston has failed. Search threads for decarbon procedure or request T88-141 from local dealer

 

what is t88-141???

 

Its a technical service bulletin describing the noise and a possible cause and repair. The service advisor can access it and make a copy for you. It is NOT a recall.

 

K, cool. I pass by a Caddy dealer twice everyday but he's only open on my way TO work, not FROM.

Thanks carnut, you have been a HUGE help to me

 

Stopped in today to the caddy dealer and got the bulletin. One of these days I'll get my printer workin and scan it and post it here


Steve