3 Typical 1 Very ODD DOHC Problem

[radman3120]

Well, I'll start with the odd one first because thats the one I really need help with. I have a '93 Z34 with the 5 speed and for some reason the first couple times I start it up in a day (I do a lot of short driving) it spews coolant from the coolant temp / intake gasket region towards the rear of the engine bay (both the sensor and gasket are relatively new). It doesnt look like it's the intake gasket which I had to replace twice this year. I pressurized the system a week or two ago (when all I knew was that I was losing antifreeze) and thought it looked like it was dripping from the threads of the coolant temp sensor so I took it off, cleaned off the teflon tape, and applied liquid thread sealant and tightened it a little further. Now it spews it but I dont know where from because its really hard to see under there. The crazy part is that after it stops spewing coolant after a couple minutes it doesnt seem to leak any more coolant. Last weekend I drove four hours to Pittsburgh and did not lose any coolant. Has anyone had experience with this at all?


Now for the typical problems you should all know a bit about:
(1) Long Start - it always starts on the second try
(2) Random Idle Speed Increase - When idling it will randomly rev the engine to about 2000 rpm.
(3) WOT miss / putter / something - usually at higher rpms as if the ignition system is cutting out or the fuel pump cant keep up

I tried the A/C sensor disconnect and idle relearn which seemed to work for a short time to correct the idle increase and hard start but then it went back. The other two 5 volt sensors that supposedly can also short out ignition on start, the MAP and TPS, seem to read fine. The WOT miss does not happen all the time but when it does it only happens at high rpms. I also switched the fuel pump relay out with a working relay. I think I am going to put in a fuel pump as it is the only thing I can come up with for the hard start (no prime, Im not sure I hear the pump when I start the car, and the car has to wait for oil pressure build up?) and WOT problem (Only does it at high rpms so maybe fuel isnt being pumped in fast enough and I have relatively new plugs (but I heard bosch are bad to have) new 8 mm wires and that leaves only the coils). Is there anything else I can check out?

Sorry for the long post but I need some help! - Thanks

[93Oldsdroptop]

RE: 3 Typical 1 Very ODD DOHC Problem

Get rid of the Bosch plugs and put in some AC Rapidfire 8's. That will help somewhat.

[Jazic3.4]

your leak may be coming from the distributor O-ring underneath the intake on the battery side. Replace the O-ring and apply some gasket maker as well.

[GTP091]

If there was something leaking out of the distributer O - Ring it would be oil, not coolant.

[radman3120]

I will replace the Bosch plugs with ACs soon. I never did think the car really liked them very much anyway... Its a fun job to change those plugs though.

Yes, if there was something leaking out of the distributor o-ring it would be oil and the o-ring has already been replaced anyway. The water pump is relatively new as well. I'm going to pressurize the system again and see if I can push any coolant out but I still cant get over how bad it spews antifreeze at startup but then totally holds it once warm.

Does anyone else have any ideas or suggestions?

[RollinonZ34]

First of all...im not a Mechanic so take this with a grain of salt!

Is it possible that the Head, being aluminum might be slightly warped and letting coolent leak when engine is cold. And then when it warms up, the Aluminum Head expands and closes or seals up the leak? When you fixed the distributer O - Ring, did you cut off the Tit (ha i said Tit) off that gets in the way of letting the shaft that the o-ring is on to help get it up and out to replace the o-ring. Some people do this and that is a little too close to the Bolt that holds down the lower Intake manifold for my liking. this could potentially let it leak antifreeze if that bolt hole is not strong enough to do it's job...possibly crack later because not enough strength after cutting Manifold too close to hole....just a thought. May also change pressure or vacuume till warm giving wierd idle, but probably not on that.

[radman3120]

Is it possible that the Head, being aluminum might be slightly warped and letting coolent leak when engine is cold. And then when it warms up, the Aluminum Head expands and closes or seals up the leak?

Well, when I got the car a year ago I dropped the engine and replaced the head gasket, intake gasket (twice - the first was defective), water pump, timing chain and gears, timing belt and pulleys, etc. Before putting the heads back on they were checked and found to be flat and I dont see how they would have become warped without the car being anywhere near overheating.

Also, since the engine was entirely apart there was no need to cut or grind any part of the manifold.

[Scott205]

not sure about the odd problem. I haven't had any antifreeze leaks except into the engine. Could be coming from around the intake manifold and just leaking that direction..but that is not likely and hopefully not true.


As for the fairly normal ones, I would say first, EGR valve. Anytime they get clogged they do funny things with your idle. I would say secondly (and possibly more likely) Pressure regulator in your fuel regulator. You just need to get someone with a gauge and have it pressurize and see if it can hold the pressure. This will especially cause your engine to start but not run the first couple of times when the engine has been run. If you are hearing the fuel pump it probably isn't that, but if the regulator is not allowing enough fuel, especially when hot, that is a good possibility.

[radman3120]

Within the next couple days i will be taking the car to my dads friends garage to check the fuel pressure and whatever else i can look at to test the fuel pump and fuel pressure regulator....

Also, as for the coolant leak I did some more pondering and looking around and it does look like there is a potential of a simple bypass hose but every time i try to look it is too difficult to see and the leak stops by the time i get anything taken apart. One of these mornings im going to take the air box off before i start it and look around that way

Scott205, for the EGR should i just take it off, clean it and get a new gasket or is there a way for me to test it as well?

[radman3120]

Well, its not a bipass hose, i finally actually saw the dripping..... from under ther manifold......i will have to tear it apart and see what i come up with. i will post the pictures of the leak as soon as i get my digicam with the picture on it back


p.s. - i am at school now so sorry its been a while since my last post

[radman3120]

Heres pics of when I took the airbox off and could finally actually see the drip from the engine rather than beneath it.

[93Oldsdroptop]

Could it possibly be the thermostat gasket or that shitty quick-release on the coolant line coming out of the manifold? Or maybe that bolt screwing into the manifold it goes into. Sure sounds like an expansion type leak. I'd check those two before ripping up the intake manifold.

Hope it helps, these things certainly can be a bitch!

[RollinonZ34]

There is a Plastic Clip inside of that tube that connects to the Lower Intake!! Where you have the Red Sealent...That Clip is a Piece of S**T!!! It hast to be leaking from there if not the Pipe where the Thermostat is!! Pull that Piece of S**T off and go get a connector from NAPA ...Male threaded just the same size as the piece going into the Maniflod...with it straight on this side...Then get some Heater Hose and clamp and run it to where that pipe goes...back towards the Firewall. Then just connect there with another clamp...Problem Solved, and does not cost very much to do!!! Hope this helps....Paul

[radman3120]

Could it possibly be the thermostat gasket or that shitty quick-release on the coolant line coming out of the manifold? Or maybe that bolt screwing into the manifold it goes into.

Well, the leak is further underneath than the thermostat gasket and quick release. Thanks for the input though.

[patgizz]

could it be running down the lower intake from above and dripping? i'm thinking the o-ring between the plenum and the lower intake.