: just bought a 68 deville, need some help

05-12-05, 10:55 PM
just got a 68 coupe deville convertable last weekend the car is awsome but it needs some work. overall its in good condition but here are a couple things i was hoping someone could help me with. the headlights dont work, all the other driving lights work but the headlights, i located the switch under the dash any way to test it or should i just replace it and what else should i check? now for the main problem. it has a 472 in it but it feels like it has no power at all. i was thinking it might have been the vacuum timing advance any way to check this? hopefully it is that but i'm starting to think its the tranny slipping. sometimes i give it gas and it feels like its in nuetral so i go into nuetral and then go back into gear and it works but lately its been feeling like its slipping even when i'm driving. its leaking a LOT of tranny fluid i'm not sure how auto trannys work but on my old manual car it was leaking oil onto the clutch disk causing it to slip could this be the same. if worst comes to worst how much is a tranny rebuild, and if i drop the tranny myself how hard is it on these cars? are there any sensors that would cause the tranny to act funny cause i've noticed a few lose vacuum lines and a couple sensors that should have vacuum lines going to them could this be the problem? sorry bout the long post, hope someone can help me out.

Night Wolf
05-12-05, 11:14 PM
Well, first, you have what is one of, it not *the* favorite 1960+ Cadillac in my eyes... gosh, I am jealous :)

About the hadlights, check the fuses? check the bulbs? the headlight switch is a two step switch, well, off, then parking lights, then headlights.... so it could very well be a bad switch. maybe pull out a multimeter and start testing the wires going to the dash.

The trans is the Turbo400... really hard to kill one of these things... maybe explain the problem more?

but if it is leaking fluid... it could very well be low on ATF? with the car level and the trans in park, pull the trans dipstick and read the level, add fluid as needed... having low fluid (even a quart) could very well do what you describe and produce slipping. Then the thing to do is find out where it is leaking from and replace the seal/gasket.

The transmission on these cars are pretty easy, compared to todays FWD cars, it is almost a piece of cake. There are no sensors to go bad or anything that would cause the shifts as you decribe.

At the least, I would remove the pan, clean it, replace the filter, and put new fluid in.

To get the TH400 rebuilt, would probably be around $1,400 complete, that is bringing the car to a shop and having them do it all (taking it out, putting it in etc...) not too bad considering the work that is being done.

About the power... until you get the trans fixed, I would hold off... if the trans is slipping to the point where the engine power simply is not going to the wheels, it'll feel like there is no power.... when in park, if you race the enigne up, does it sound good? responsive (as responsive as these big blocks get) or does it seem like something is wrong with the engine itself?

a complete tune up would also be good... 1968... you have points.... perhaps think about swapping in a 1973 (?) HEI from a 472/500.... probably one of the best things you can do for the car...

05-12-05, 11:46 PM
gave it a full tuneup a couple days ago the engine sounds good but i dont really have anything to compare it too my other cars have been a datsun 510 and an 89 supra, i've never dealt with anything like this before. i tried tracking down the leak its leaking right onto the exhuast piping so it was smoking a lot i'm gonna take a look at it again tomorrow after my finals. part of the tranny doesn't have a cover the converter and flywheel are exposed and the fluid buildup is right under that. i'll remove the pan and check that out and give it some fluid i'll let you know how that goes tomorrow, i really appreciate the help night wolf its been hard finding info on this car

05-12-05, 11:54 PM
Night Wolf hit it all pretty much on the head. It does sound like you might be just low on fluid. You need to check and fix it if needed. He might even be alittle high on the price to rebuild....

I also have a 68 convertable and also think its the best looking yr... but thats also because I own one.

Mine runs great and have found that a lot of the people who start changing things (carb being the biggest) end up with worse then when they started. Its easy to read something get excited and start ripping into things

Its a caddy, the best car on the road in 68, that means that it is still better then 50% or more of what is out there today.... Just put it back to the way it was and "Forget-About-It"

Keep er clean & treat er mean.....

Best of luck

05-13-05, 12:44 AM
Headlights... these are actually powered via seperate circut running through a fusible link right from the battery lug on the starter to the switch, containing an internal circut breaker to the headlights. Parking lights are through the fuse panel inside the car. See if a fusible link is shot down by the starter. give them all a gentle tug. If one is stretchy like a rubber band, its bad. Could also be the dimmer switch on the floor. Make sure it is getting power.

Feels slow? Where is it leaking from? theres few vacuum lines on these cars unless you have the auto climate control, and that is merely fed from one vacuum line from the engine. From the engine, there should be a vacuum line to the brake booster, transmission, vacuum manifold on the firewall, AIR pump, and distributor. In factory configuration, the lines do not directly run to the distributor. They run to a thermal switch located on the drivers side cyl head. This has three lines on it, one is manifold vacuum, one is ported vacuum, and one goes to the advance on the dist. You can eliminate the switch if you feel it might be causing the problem by using the ported vacuum line and running it directly to the distributor. When you did the tune up and replaced the rotor, did the centrifigual advance mechanism look ok? It shouldnt bind up at all. Also, is the choke opening up properly? What about say, half throttle (or until you feel an extra tug of resistance in the accelerator) For some reason, people love to "fix" the secondaries. If you keep the car out of the secondaries, how does it behave?

The tranny is not hard to deal with. I echo the thoughts of fluid level being a problem. Where is it leaking from? If its leaking from the bellhousing area, it will likely need to be pulled to get to that seal. Almost any other place is servicable with the trans inside the car.

And yes, it is definitely the best looking year. :yup: :D (I own one as well)

05-13-05, 10:36 PM
davesmed you were right about the headlights, i spent my afternoon installing a need headlight switch it didn't work so i reread your post and went out and found that button on the floor, pushed it and the headlights came on. what is the point of that thing anyways?

Night Wolf
05-13-05, 11:12 PM
The switch on the floor is the headlight dimmer switch.

new cars... well, GM atleast have it where you pull the directional lever back for high/low beams, imports have you push the directional forward.. I think they used that for a long time....

my '79 DeVille has the switch ont he floor... both my '89 Oldsmobile and '93 DeVille have it on the directional.

If the lights come on only when you hit the switch, then I bet the headlights are bad. You have the stacked headlights, 2 on each side, now I am not sure which function for high/low beam etc... but you may only be getting, say the high beams, and when you push the switch for low beams, the bulbs are bad. I believe they may even be dual element bulbs.

and... no offense to your other cars, but the Caddy is wayyy cooler :) Although the Supra can be a fast little bugger....

Also, the reason why I said $1,400... that is what it cost my mother in her '89 Brougham, then again it is a 4 speed (TH350? I don't remember) so the TH400 is probably cheaper, not to mention the damn things were used in everything so any transmission shop can repair it, and parts are cheap.

If it is your thing, maybe get a shift kit installed... these trans were made with excessive slipping in mind to have the non-detecable shifts, but it is also hell on the clutch plates. a simple shift kit will firm it up and extend the life of the transmission... but you'll feel the shifts.

Also, install a transmission cooler... huge car = lots of heat buildup in the transmission, so a $40 trans cooler form the auto store would be a very good thing to get.

Finally, you said the torque convetor and fly wheel are exposed? I don't see how that can happen unless something really strange is going on.... can you get any pics? (of the car too :) )

05-14-05, 05:19 PM
now the brights and the regular lights work, this electical system is CRAZY. i'll take a pic of what i mean by part of the tranny being exposed when i find my digital camara and i'm also gonna take pics of the step by step process of changing the headlight switch in case anyone needs that as i had a really hard time figuring out how to do that.

05-16-05, 02:45 AM
just got a 68 coupe deville convertable last weekend the car is awsome but it needs some work. It has a 472 in it but it feels like it has no power at all.
Same thing with my '70 Sedan de Ville... it has nowhere near the power that my '69 Fleetwood Brougham has. The '69 has dual exhausts, but the '70 still should have almost as much power.
My '69 will easily burn rubber from a standing start; even from a rolling start. And I've timed it doing 40-60 mph in 4.0 seconds. No way can my '70 burn rubber from a standing start- but my family's former '70 Coupe de Ville certainly could.
I'm guessing either the secondaries aren't opening on the carb, or like yours maybe it's the vacuum advance.
I haven't looked into it yet, but when I do I'll post the diagnosis.

05-16-05, 11:46 AM
First of all it's a DeVille Convertible, not a Coupe Deville Convertible get it right!:D

I own one too and can say that :thumbsup:

and yes they are the BEST!

Now your headlight switch, (dimmer switch), that switch routes both high and low beams so if it goes bad (or breaks like mine did) then you get NO lights :eek:

Transmission. Check to ensure that a vacuum line going to a solenoid of some sort on the passenger side is not loose, This can get pulled off by accident and it will leak like crazy (I know - still trying to clean the garage floor) and you'll not get proper shifting.

I'll have to re-read carefully to see if there's other things to check.

Check all the vaccum lines these cars actually run on vacuum - the car converts the gasoline to vacuum and uses that to power the car. :gungrin:

Other than leaking seals and that line that came off one time, I've had no problems with my transmission for 166,000 miles!

05-16-05, 01:49 PM
You should go ahead and replace the vacume advance and the points its less then a $20 fix and then you know it will work. When I first got my 69' I replaced those and it really came alive. Also the carburator as somebody mentiond above, the factory quadrajet's are not known for making much power especially an old one. If you replace the carb you will notice a big difference.

Also the vacume lines you are talking about that are not hooked up you should find out what they go to in a manual and hook them up some could be to the A/C one ahould be running to the tranny and if they are not hooked to anything but are plugged in (drawing sucktion) then that is a vacume leak which would make it run funny.

As for the tranny cover I belive you are talking about the bottom torque converter cover and it is not a must...It missing is prolly a sighn that the tranny has been out or worked on before.

05-16-05, 06:05 PM
where did you get the vacuum advance solinoid i've been to all the local parts stores is this something i need to get from the dealer?

05-17-05, 10:00 AM
Vacuum advance is not a solenoid. It's a conical shaped aluminum thing that afixes to the distributor under the points plate, and has a vacuum line going to a multi port switch on the front of the engine.

05-17-05, 02:25 PM
I got mine from my local Autozone.

05-25-05, 07:50 PM
I replaced the vacuum advance this morning holy crap this thing has some power thanks for the help!