1990 Nissan 300ZX

Engine Mechanical problem
1990 Nissan 300ZX 6 cyl Two Wheel Drive Manual 130k miles

Hey guys two questions actually on my 90' 300zx TT. One is when I first started this car up the exhaust was white with some oil in the tail pipes, exhaust wasnt white after 5 min of driving, however there was oil on the middle underneath of my hood and smoke coming from the top middle part of the engine. The guy I bought it off of said he just replaced the intake gasket. Possibly a botched job? Also there is a coolant leak that I cannot find, the car starts to run hot after about 10 min of driving and smokes in the front of the motor driver side. This is not the original motor. It has about 70k on it. He said the oil issue has been going on for a while and just adds a quart as needed.
October 8, 2009.

Hello -

To better assist you is your model is the 300ZX 2+2 and what is the engine size in liter

Oct 9, 2009.
HAs the oil and oolant mixed in the radiator or engine? To me it sounds like a bad head gasket, leaking valve cover, and a water pump leaking. Have you tried to pressure test the cooling system? Also, check under the water pump. There is a weep hole that will leak coolant if the bearing or seal is bad in the pump.

Also, steam clean the engine and drive it to see if you can determine where the oil is coming from.

Let me know what you find.

It is a 3.0 v6 twin turbo 2dr coupe 1990 300ZX.
He just replaced the water pump and intake gasket on it. Maybe he botched the jobs? I checked the oil and it was not white. It was the typical dark oil color. I have not bought it yet and was trying to establish how sevre it could be. I hope its not a blown head gasket. That would probably be a deal breaker as those are still really really bad right? Thanks alot guys!

Oct 9, 2009.
Honesty, if it is a head gasket, it could get really expensive. The parts won't be too bad, but the labor will kill you. Also, if he just replace the head gaskets and they are leaking again, chances are you have a warped head that will either need machined or replaced. Again, that is another expensive job.

I don't know what he is asking, but you may want to reconsider.

Normally, I don't make recommendations like that, but it the problem was there, (fixed?), And it's still there, chances are it's going to be a bigger problem than what you, he, we. Expect.

Let me know if you have other questions.


Joe, do you think its the head gasket because it has an oil leak and coolant leak? He replaced the intake gasket not the head gasket. The coolant leak that is smoking is coming from the front driver side of the motor I guess by the headlight area and the oil leak smoke is coming off the top part of the motor in the center. So whether leak locations have anything to do with it I dont know. He also did alot of the work himself not a certified mechanic, which concerns me a little. He is asking 2700 for it. Thanks again for all of your help!

Oct 9, 2009.
If that is the case, then chances are it isn't the head gasket. But I have to question why, if he replaced the intake, he didn't fix a simple oil and coolant leak. As far as the coolant leak, check the heater hoses. I believe they run from the front of the motor (water pump area) to the heater core. There could be a leak there. Also, take a flash light and check along the intake to make sure coolant isn't leaking there.

As far as the oil, if it is in the center of the engine, check to see if the oil is leaking from the valve cover gasket and running on to the exhaust manifold. With the engine running, open the oil fill cap and see if there is a lot of pressure coming from there. Let me know what you find.

I hope you understand. I am trying to be cautious because you really don't know the vehicle. I don't either. Will he take less for it? Maybe if you offer him 2200 at least you would have 500 to work with to fix the problems. Will he let you take it to a mechanic to look at it?

If you're near Pittsburgh, I could check it for you, but chances are you're over a thousand miles away.

Let me know, and honestly, the fact that it runs hot after about 10 minutes makes me question the headgasket unless the coolant is leaking bad enough to be low after that amount of time or the cooling system needs flushed.

Finally, there is one more thing I need to know you checked that we haven't discussed. Make sure the floor and the subframe is solid and not rusted. THey have a history of rust problems there. Again, if you live in CA or AZ, that shouldn't be an issue, but here in PA or anywhere salt is used to melt snow, most of them rusted. Make sure nothing looks like it was just reundercoated or painted.

Let me know. My gut tells me NO, but I can understand your interest in the car. They were really fun to drive. I had a 240Z with a straight 6 cylender and 6 webber sidedraft carbs. Those were the days. But as many of them did, the floor and frame fell apart.

Please let me know what you decide or if you have other questions.


Joe, when I went to inspect the car the other night, one thing I did as far as the coolant leak is put about 4 cups of water in the rad. And watched for any leakage under the car, but I found none, and while driving it maintained a good temp until the very end it had raised a little and the smoke that did come out did not smell sweet, more like just water steam. SO I am really hoping its just a heater hose or something less complicated.

He has agreed to let me take it to the Nissan dealership on tuesday to do an inspection on it. I live in illinois or else I would take you up on your offer. So yes I do live in a state where salt is used, heavlily. So I will be adding that to my list of things to check out at the dealership.

As far as the oil, yeah it doesnt make a lot of sense to replace the intake gasket and replace the water pump etc, and not fix an oil leak. If there is oil being caked on the hood could it still be a valve cover leak? I would think the oil would have to be pressurized in order to get on the underneath of the hood. I honestly am thinking it is two seperate problems, but maybe im just in denial. I do have a ton of interest in this car, which is why I am still actively pursuing it.

I will let you know what they said about the pressure coming from the oil fill lid which im thinking is as simple as the place you put oil in right haha.
Thanks a lot for the help!

Oct 10, 2009.