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Cadillac Deville - Vacuum leak

babelfish69babelfish69 Posts: 2
edited October 2014 in Cadillac
I recently acquired a Cadillac from a friend. It’s a nice car, but the catch is it will run but it barely idles. If you step on the gas the engine dies. He gave up on it after a guy he knew “fixed” it for cheap. They had a sharp dispute and parted company on bad terms. My friend shelled out several hundred dollars for a car that was useless to him. This supposedly knowledgeable car person, who isn’t part of any auto repair outfit, offered to put new intake manifold gaskets on to fix a coolant leak. That doesn’t quite make sense to me. What does the intake manifold have to do with the cooling system? This is my first Cadillac, so maybe there’s something I don’t know yet. Also my friend said the car ran perfectly before this guy got his hands on it. I checked and re-checked all the vacuum connections around the throttle body and followed the lines to their connections. Everything was fine. I hooked up a vacuum gauge and fuel pressure gauge. The fuel pressure was fine, but the vacuum gauge barely registered any vacuum while idling. I made sure the gauge was working by hooking it up to another automobile, and it was. So it seems to me that the guy must have messed something up putting the manifold back on. My question is if there is any way of isolating the vacuum leak, or do I just have to take the intake manifold off and replace the gaskets again? And am I right to assume it’s a leak somewhere around the manifold? Or is there any other area I should check? The guy also was supposed to put valve cover gaskets on and change spark plugs. I found three new gaskets in the trunk. By looking at a parts supplier online I see that two of them would be from the intake manifold gasket kit. One is squareish, about 3” by 3” with three bolt holes. The other is round with a projection, and has nine bolt holes. The last gasket looks like it comes from a valve cover gasket kit. It has eight circular holes, and four bolt holes. I’m not sure what these gaskets are for until I start taking things apart. I’m not sure why he didn’t put these in. Anyway, any suggestions about if I’m on the right track would be appreciated. I don’t want to tear things apart unless absolutely necessary.


  • bolivarbolivar Posts: 2,316
    Well, it sure would be nice to know the year, model, and engine we are looking at.....

    Spray starter fluid or carb cleaner around the edges of the intake, or any other hose or area thought to have a vacumn leak. If the idle changes, increases, there is a leak there.
  • Sorry, I should have included the specs. It's a 1993 Sedan Deville with a 4.9L engine. Thanks for the input. Someone else told me to check the timing. I did think of that, but don't currently have a timing light. I haven't had one since I sold my 1969 mustang. So I ordered one today. I did check the firing order right away though.
  • bolivarbolivar Posts: 2,316
    Ok, I can't give you specific help, but maybe some guidance.

    This motor has a complicated 'idle speed motor' and maybe another idle controller. And they are hard to 'set up', per what I have read. I don't think there is a timing problem (save your money on a timing light), I think most timing is controlled by the computer by 1993.

    You need a service manual. A Haynes or other cheep one might have the needed steps to set this up, and then maybe not.
  • jlewis6jlewis6 Posts: 6
    I've got a 99 cadillac Deville that I've been told has a vacuum leak from the intake manifold. I was also told it has a coolant leak. I am currently blowing white smoke out of the tail pipe on start up. Once the engine warms up to 104 degrees, it quits smoking from the tail pipe as well as when I go down the road. This problem is a nightmare to me. This motor is a used motor, 4.6 liter, that I had put in that had on ly 56k miles on it. Since putting the motor in, I have battled with external coolant leaks coming from poorly placed hoses and clamps. Finally it was determind that i had a bad thermostat housing assembly. The same mechanics that put the engine in replaced the the thermostat housing assembly. One week later, the check engine light came on and so did the low coolant alarm. Enormously frustrated , I took the car back down to the same mechanics, and they said I had a vacuum leak in the intake manifold. I felt like I was being taken for a money ride so I had another place take a look at it. They told me I did not have a vacuum leak. in fact, the mechanic said he saw coolant on the nr.1 spark plug, and the computer indicated a possible head gasket problem. My car is currently driveable, has power and does not sputter like an old time pressure loss around a head gasket. However my question is: Is it possible that a vacuum leak from the intake manifold could cause a coolant leak into the cylinders, and if so how. How can I be absolutely sure it is not the head gasket?
  • a vacuum leak will not let coolant into a cylinder. this does sound like a head gasket problem, esp if it has been overheated a few times. these heads warp easily and headbolts tend to stretch easily. they should be replaced when doing headgaskets. this engine is also prone to the threads in the upper headbolt holes coming apart
  • jlewis6jlewis6 Posts: 6
    So far, my temp. gauge has not gone past 192 degress, however if I let the car sit for a week and then crank it up, after 1 minute white smoke comes out of both tail pipes for about 5 minutes then quits. I'm so afraid that the car is not worth keeping . Can Someone tell me what it migh cost to tear the engine down to tighten bolts or replace bolts to stop this problem?
  • bolivarbolivar Posts: 2,316
    If you are not having any overheating, why are you concerned about some white smoke out the exhaust? This very well may be condensation. When the exhaust system heats up, the color changes.

    The price for a head gasket job on a Northstar is very expensive. The motor must be pulled to get to ther rear head. The heads removed, the bolt holes bored out and then re-threaded and steel inserts screwed in. The head, with new gaskets are then reinstalled, with the new head bolts screwing into the inserts. This usually stops any future head gasket problems. The cost for all of this is probably $3,000, more or less.
  • jlewis6jlewis6 Posts: 6
    If my coolant leak is in fact loose bolts connected to the head gaskets or head gaskets, how long can I continue to drive this car in it's present condition? I still haven't overheated, but have been keeping a check on the overflow tank because it was discovered that I have some coolant getting into the nr.1 cyclinder.
  • bolivarbolivar Posts: 2,316
    Well, if it is so bad that coolant is getting into a cylinder, I can't believe it's not alreay overheating.

    Have you just been driving 'easy'? Slow accelerations and not been driving very fast? This might keep it from overheating, especially on short trips.

    Take the car out and accelerate it hard a few times. Find the steepest hill and run it up the hill, fast. It will probably overheat.

    If the car overheats and is not then totally abused by continuing to drive it, the Northstar motor is usually not hurt by a head gasket failure. Pull the car over and let it cool and refill the fluid to get the car home, slowly. It it overheats almost instantly, the car probably should be towed. The heads usually are fine, and the block does not warp. You just have the huge expense of having the bolt holes fixed up. That and new gaskets, other misc parts, and the motors are usually fine.

    It's just when you need $3,000 or so to fix a $6,000 car (or less), it just is not worth it.
  • jlewis6jlewis6 Posts: 6
    When driving up steep hills and distance. My question is: 1. How long can I keep driving this car in this present state? Will the engine sieze up? Do I just need to keep an eye on the over flow tank for coolant levels?
  • bolivarbolivar Posts: 2,316
    So, you really want an answer to this un-answerable question?

    Drive it until it seizes. Then you've driven it too far. This is the best answer I can give.
  • jlewis6jlewis6 Posts: 6
    My question then is this: 1. Is overheating the only way to tell if this loose head bolt, overboring of the block concept will hold up? Will the engine start to skip?
  • bolivarbolivar Posts: 2,316
    -There supposedly is a test kit that can be bought at parts houses. It tests the coolant for combustion by-products, which indicate gases from the piston are being pushed into the coolant.

    -A correct 'Timesert' installation (overboring of bolt holes and steel inserts) is supposed to pretty much cure the head bolt problem.

    -Don't know about 'skip'.

    Is your motor overheating or not? If you are just losing coolant and it is not overheating, you have a leak somewhere. Unless your are in the early stages of a head gasket failure.
  • jlewis6jlewis6 Posts: 6
    Was done by the same guy that put the used motor back in 07 my Deville. The color in the tube was light green. He said he wasn't sure if it was the head gasket, but noted he had to take more apart to see if coolant was getting in on other cylinders. At that point, I felt like all I was doing was just throwing money into a hole. So first: 1. What does the color light green liquid mean is what I saw in that tube, the mechanic showed me?? And 2. My car is currently not running hot. I have not driven it over 25miles a jaunt and back once or twice a week at best. I am currently noticing that I am using more dexcool as it is probably getting mixed with the combustible gases and thats whats burning out of my tail pipe for about 20mins , then turns clear as motor is hot. She still drives good when driven and with same power and take off. I do need to do something soon becasue I also noticed just recently that my surge tank is starting to seep, probably due to pressure back flow into the surge tank with heat. Any suggestions besides push it off a cliff.? Can I get this problem fixed for under 3000 dollars? And i really can't afford that??
  • bolivarbolivar Posts: 2,316
    1) No idea, you need the instructions for that test kit.

    2) If it's not running hot, I would look for a leak.
  • al03al03 Posts: 1
    I have a 96 cadillac deville and have some issues with it the radiator was changed and every now and again i get the check coolant level light come on and have to fill it up again,also my car has a new blower motor and the air does not come in thru the face vents it comes in thru the top and bottom.Another issue I have is that the service emissions light comes on with the service engine soon light,It was off but a couple weeks ago i did some routne maintenace on it and it keeps coming on. I know thease things are minor but this car has only 93,000 miles on it and i would like to fix all thease things in 1 day what kind of parts should i buy or can you help me.
  • Are there a safe head gasket sealant?
  • bolivarbolivar Posts: 2,316
    No sealant will stop a Northstar's blown head gasket.

    Prepare to spend big money or send the car to salvage.
This discussion has been closed.