Coolant problem....

[Boog]

Hey guys, have a problem I was hoping to get some input on.

 

I bought my 280z almost 8 months ago, and let me start by saying that this problem wasn't there when I got it. Over the last few months, my car has been smoking more and more on startup. It goes away after it heats up, but it really billows smoke while it is still cold. It also happens if I turn the car off (after it is warmed up), let it sit for a few minutes, and start it again. I believe the smoke is coolant because it doesn't smell like oil smoke and it is white. It also smells similar to the steam from opening a hot radiator. It doesn't leak coolant from the block anywhere onto the ground, but it does go through quite a bit of coolant. I have to add a quart every week or two or the temp will start to creep up while driving or the heater will start to get moody on me. I am mainly looking for a diagnosis, mainly because in a month or two I am swapping in a brand new motor my friend is rebuilding right now, and I just need a diagnosis and possibly a temporary fix for the time being. I love driving her and I don't think I can go without, let alone afford all the coolant. 

 

Thanks in advance, happy wrenching.

 

(Additional info: 1976 280z, L28 block, not sure what headit has off the top of my head, but I doubt it would make a difference? Also is completely stock (the engine at least, lololol))

[MikeRL411]

Most likely a bad head gasket. Have you ever retorqued it?

[racerx]

do a compression tst for now.

[Boog]

@MikeRL411 No I haven't, I'm not much of a engine mechanic yet, does this require head removal or can I do it without? 

 

@racerx Planning on buying a testing kit tomorrow, will report back with numbers at some point soon. I figured that might tell a bit more.

[racerx]

if you do buy a compression checker buy the screw in type one not plug in.  You may also want to buy a remote starter...so that you can check compression whule you click away with the remote stsrter.

[Boog]

@racerx That's what friends are for, hahaha

[racerx]

yep..whatever works..it's just that later on you want to work on your car and friends will not be around..this is where remote starter and screw in type comp. check comes in handy.

[I'm BLUE]

Agree with all of the above.

 

Compression test with all spark plugs out , throttle open , and record clicks.

Leak-down tester is very helpful as well.

The chemical kit to drop in the coolant is effective but can be expensive ( as in put the money in the gaskets/parts in the first place type deal ... )

 

Look for the CLEANEST spark plug (when you pull , take pics , and number ) if you believe coolant is getting in there (sometimes it's clean...)

The port that is the CLEANEST will likely indicate the problematic cylinder (not always but sometimes depending on engine condition).

Don't worry too much about slight pitting on the block surface around the coolant areas , but make note if it's really bad ... a good portion of l-series 6-cylinder engines I have worked on have all had a bit of this. Hard to get away from it.

 

If you have a stock manifold ... and conclude a bad HG.

pull the head with the manifolds attached... (at least I do)

Much easier to get at everything (manifolds as well) with the head on the bench working out of the car.

 

If you have a header this is not likely an option as you know lol.

 

HG's pop quite a bit ,,, age ,, neglect ,,,etc ,,,, better to do now then to be sorry later.

Make sure to have a machine shop pressure test for cracks , and they will check for warpage for free typically.

It's like $40-45 ? for a pressure test.

or access to a professional flat-bar (friend ?)

 

The head will likely be an N47 with exhaust liners. ( but are switched around so much it's hard to conclude/assume... )

Prepare for the front AND rear studs/bolts (whatever lies there at this point) to break or give you problems...

(((be ready to drill out studs.. have done it a few occassions and it's very typical... I use right and left hand drill bits rather than extractors... either works)))

be very careful on the rear engine hook point.. sometimes it's loose and sometimes they are rusted or just fine to use... ( I've had one break on me while lifting the engine 1-2 inches vertically.)

 

Look at doing front and rear main seals while there if you want to run the engine a bit longer and check timing chain stretch/slop before pulling the head.

10mm allen head bolts and clean the recesses of the head-bolts thoroughly BEFORE sticking the bit in and... un-torqueing the head in sequence (sometimes they are gunked really badly..)

 

At this point in time with datsun's ,,, I consider Head Gaskets , Front and Rear main seals ,  slave cylinders , to be maintance and not a repair.. when I purchase them :lol:

 

Take pictures as you go , and label things you don't know.

Easy peezy.

 

Good luck :)

[Boog]

Wow, thank you for all the info. Unfortunately, I just replaced all my plugs a week ago so I would imagine they are all relatively identical at this time. I wish I was more experienced or I would have already pulled the head and replaced the gasket. Would I remove my head and take it to a machine shop for that testing you mentioned? I didn't get to buying a compression tester today, but I hope to get it by Wednesday. Again, thank you for the info.

[kelowg]

Ck intake manifold,if any coolant lines connect to it,ck all nuts or bolts. Could coolant leaking into intakee runners

[racerx]

quick test if you have blown headgasket...when you warm up the car, go to the back by the exhaust and smell the exhaust.  If it smells like coolant, then maybe blown gasket.  Also check your dipstick and if oil looks like choc. milkshake, another indication.  Good luck..keep us posted.

[datzenmike]

A compression test may not show a leak into the water jacket.

 

Fill the rad and warm it up with the cap off. Rev it several times and watch for bubbles. This is combustion gasses forced int the coolant. The coolant may have a faint gas smell.

 

I agree with DPT. You can check the head for flatness yourself with a straight edge and a feeler gauge, no a yard stick won't do. Borrow one it's cheaper than having a shop do the same thing and the answer is honest. For a 6 cyl no more than 0.006" lengthwise and 0.002" across.

 

Block and head surface must be absolutely CLEAN. You can't have it too clean.

Threaded holes in the block must be tapped or cleaned out thoroughly

Head bolts are totally reusable if undamaged, clean and wiped with an oily rag.

Do not ever use sealers. (Nissan didn't) Gaskets are mounted dry!!

Tighten bolts starting in the middle and working progressively outward to the ends in three stages starting with 20 pounds then 40 and a final 60 ft lbs. I don't have the procedure or exact amounts.

[Boog]

Thanks for all the input guys, I am going to read over all the comments again and take everything into account. One question left un-answered: why does the car only smoke on startup? What does it go away with the engine being warmed up? I am almost positive that the leak is heat related, and that something is expanding and slowing the leak with heat. Is this possible with an intake manifold, or wouldn't it be more of a head gasket problem?

 

Again, thanks for all the comments.

[racerx]

My datsun smokes, specially in the cold. Smoke is white. The smoke should go away once the car is warmed but may smoke still, specially when cold.

[datsunaholic]

It goes away because everything expands when hot, which probably seals whatever leak you have.  Or, it's getting hot enough to make the steam less saturated and invisible.

 

The reason it's more visible now is because it's that time of year.  Come summertime you'll probably notice it a lot less, but the problem is still there.  It won't get better with time.

[Boog]

Thanks for the assurance, but I still feel like my car is smoking more than you think. It literally BILLOWS smoke, and leaves a cloud outside my house for a few minutes. It darkens the sun. 

 

Maybe I'll take a video to show you what I mean.

[racerx]

What color is the smoke and like.mentioned earlier stand by the end of car and smell exhaust

[datzenmike]

White.... steam. Could be natural moisture that's visible like your breath in the winter... or could be coolant that has dripped into the cylinder overnight and is being boiled off. If so you will have noticed the coolant level constantly dropping.

 

Blue...... burning oil. Again oil that has dripped down worn valve stems overnight. Burns off on start up.

 

Black..... Gas that is not completely burned. An over rich condition on carbs, possibly flooding, or choke on or adjusted too rich. On EFI possibly a MAF/MAP malfunction, dirty sensor...

[Boog]

Took a video. Hope you guys like it. Smoke is pretty white. The real smoking starts around a minute or so.

 

http://www.youtube.com/watch?v=Qli-ZxIO6CE&feature=youtu.be

 

So the smoke smells like normal exhaust, with maybe a little bit of coolant smell. This was a cold start, and after I drove it to the store and let it sit in the parking lot for 10 minutes, it started up with a little smoke for about 30 seconds. It was also popping when I gave it gas, like the cylinder wasn't firing correctly? Went away after a few minutes. 

[datzenmike]

I've seen this much when it's cold out.

 

You said you were replacing coolant? No leaks in the driveway? then could be the H G.

[Boog]

Engine actually started running hot near the store and I had to top off the coolant, about 2 cups or so. No leaks. Has been about 10 days since the last time it started heating up.

[racerx]

Did you try smelling the exhaust and look at your dipstick?

[datzenmike]

I've seen this much when it's cold out.

 

You said you were replacing coolant? No leaks in the driveway? then could be the H G.

Do you have a coolant recovery bottle or does the rad overflow just dump out on the ground? A worn gasket on the rad cap could be squirting out coolant every time you shut it off hot. Have you noticed coolant on the ground? Well, when it's not raining that is???

[racerx]

should also check the belt, maybe too lose. Also check timing could be retard.

 

So far here is a list of free things to do.

 

1). check compression

2). smell exhaust at back, if is smells like coolant then HG bad.

3). Check resevoir if no resevoir then disregard

4). check timing, maybe retard

5). check dipstick, looks like malt shake, then HG

6). also check your spark plugs since you will do comp. check anyway.

 

Good luck.

[datzenmike]

Plugs yes. Steam will clean like nothing else. I blew a HG on my L20B and the bad cylinder was half clean. The carbon that was left fell off to the touch. Piston top was spotless!!!