Cadillac Owners Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
171 Posts
Discussion Starter #1
I am interested in a very clean 80's model Cadillac, around 60K miles, well serviced and pampered .... but with the HT 4100 4.1 engine. I have heard so many negatives about this engine. Should I avoid the 4.1 engine? There are other Cadillacs (and other makes) that I like from the 80's/early 90's that do not have the 4.1. What would you recommend? Avoid the 4.1? Thanks!
 

·
Registered
'87 SDV
Joined
·
1,296 Posts
Depends a lot on what year. The early RWD cars had the most trouble, because the engine was not designed for them. If it's an '82 or '83 full size RWD, I would be cautious but not run from it. Check the valve covers. If they're chrome or black with aluminum fins, it's the original engine (not a deal killer, but not the best news). If they're a plain black cover, it's been replaced with an updated engine (very good). If it's an '85 to '87 FWD car, there is much less to worry about.

On the car you are looking at, check for any sign of oil/coolant contamination: i.e. a milkshake color to the oil on the dipstick, or black oily slicks in the radiator or overflow tank. If the coolant is the color of a cup of coffee, that's very good - it means the cooling system sealer has been used.
Also check trouble codes on the onboard diagnostics (see the sticky post at the top of this section for instructions).

The 4100 got a bad reputation for several design flaws, most of which were resolved in the FWD cars of 1985-87. The primary problem areas are head and intake gaskets, weak camshafts, an overloaded distributor gear, and weak timing chain sprockets. But the truth is the catastrophic failure rate of 4100s under warranty was not that high. In fact, the 4.5 and 4.9 engines, which were updated versions of the 4100, remain some of the most reliable engines Cadillac ever produced. Plenty of people (myself among them) have driven 4100 powered cars for years with no serious issues. Mine gets 25 mpg on the highway and purrs like a kitten.

The three keys to success with a 4100 are:

1) Get a service history if one is available.

2) CHANGE THE COOLANT EVERY YEAR AND USE THE GM SEALER SUPPLEMENT TABS.

3) If you're mechanically inclined, purchase a Factory Service Manual for your year and model car. It can save you a fortune in labor.

These are complex but not terribly complicated cars, well within the skills of the average shade-tree mechanic. By comparison, consider that large numbers of pre-2000 Northstar engines have similar head gasket problems, but they are so complicated hardly anyone but Cadillac dealers can even work on them. Head gaskets on a N* mean dropping the entire engine cradle out the bottom - thousands of dollars. On a 4100 - you can have the job done for less than a grand, or do it yourself for less than $400.

Just go into it with your eyes open. Any old car is going to have things go wrong, and keeping a luxury car on the road is going to cost more than a Corolla. But then, a Corolla doesn't ride like - or have 1/100th the class of - a Cadillac.
 

·
Registered
1987 sedan deville
Joined
·
68 Posts
Great advice Noahsdad. I also own a 87 deville. Just turned 160,000 miles and basically everything on the car is original. 23mpg around town, 27-28 on the highway.
 

·
Registered
1987 Eldorado
Joined
·
82 Posts
Great advice Noahsdad. I also own a 87 deville. Just turned 160,000 miles and basically everything on the car is original. 23mpg around town, 27-28 on the highway.
How do you guys manage that good gas mileage?

My 87 Eldo with 53,000 miles gets 16 mpg town and 22 mpg highway.

I have replaced plugs, cables, oxygen sensor, EGR.

It idles a little rough and stumbles when I floor it.

What else do I need to check.
 

·
Registered
'87 SDV
Joined
·
1,296 Posts
How do you guys manage that good gas mileage?

My 87 Eldo with 53,000 miles gets 16 mpg town and 22 mpg highway.

I have replaced plugs, cables, oxygen sensor, EGR.

It idles a little rough and stumbles when I floor it.

What else do I need to check.
A lot depends on the grade and quality of fuel you use, and on how and where you drive. The stumbling idle and flat spot could be a slight vacuum leak, or misadjusted or faulty TPS. Check trouble codes.
 

·
Registered
'99 Eldorado, '04 DeVille
Joined
·
194 Posts
I worked at a Cadillac dealer in the 80's when those engines were new. The main problem we saw then was leaks from assorted places. With the zinc virtually gone from motor oil now, on older engines you are better off running a diesel-rated oil that still has zinc in it. Most are 15w-40 but if you dig a little you can find thinner oil if it gets cold where you live. I always thought it was a nice smooth-running engine with decent power for its size.
Just keep a sheet of cardboard under it.
 

·
Registered
1987 Eldorado
Joined
·
82 Posts
A lot depends on the grade and quality of fuel you use, and on how and where you drive. The stumbling idle and flat spot could be a slight vacuum leak, or misadjusted or faulty TPS. Check trouble codes.
The only trouble code I get is E048 EGR System Fault. The check engine light comes on infrequently (about every 2 weeks). I had changed the EGR last year.

I am starting to suspect either ignition (have never changed distributor cap or module) or the fuel pump.

If I can find a fuel pressure gage I will check that first.

Any suggestions?
 

·
Registered
1995 FWB 128,*** miles
Joined
·
2,247 Posts
The only trouble code I get is E048 EGR System Fault. The check engine light comes on infrequently (about every 2 weeks). I had changed the EGR last year.

I am starting to suspect either ignition (have never changed distributor cap or module) or the fuel pump.

If I can find a fuel pressure gage I will check that first.

Any suggestions?
A vacuum leak could cause EGR problem.
 

·
Registered
Cadillac
Joined
·
72 Posts
I am interested in a very clean 80's model Cadillac, around 60K miles, well serviced and pampered .... but with the HT 4100 4.1 engine. I have heard so many negatives about this engine. Should I avoid the 4.1 engine? There are other Cadillacs (and other makes) that I like from the 80's/early 90's that do not have the 4.1. What would you recommend? Avoid the 4.1? Thanks!
God, when will Cadillac get it right? (never) Im going through all this BS with a 1999 Cadillac STS- So far Ive spent 10k on getting it right.....AND I was a Master Auto Tech only a few years ago- just not on Caddy's. A shop owner I know who has been in the businesss for 38 years said it the best. After the early-mid 1970's Cadillac is a 1 owner car. In other words, they are great for that large company CEO for 1-2 years.....after, a toilet on 4 wheels. To bad some look and drive so nice (if your lucky) - Oh ya, stay away from Cadillac "specialist" Custom Innovations in WI- take it from me. Look em' up on ggogle and read the posts.!:stirpot:
 

·
Registered
1986 Coupe Deville
Joined
·
138 Posts
Alot of people bash the mid 80"s HT4100 engines Mine has 172,890 miles it was always well maintained never overheats. I agree it had some flaws in the engineering (a cast iron sandwhich aluminum block cast iron heads and aluminum intake ) you need to get a maintainance history especially on the cooling system. A well maitianed engine will last for years. In my case 21 years and going. Good luck

Tallpat
 

·
Registered
92' Eldorado, 97 Catera
Joined
·
289 Posts
There are a couple places that make the 4.5L to fit the early 80's configuration. These engines are way more dependable and have a little more power.
 
1 - 11 of 11 Posts
Top