I've developed/noticed two problems going on with my 85 recently.

#1 When I start it up from cold, say sitting overnight, it immediately comes to life, but dies. On the second start, it stays running, but its quite rough until the coolant temps reach around 170, then it smooths out quite a bit. It bucks at lights and almost stalls at stops until that point though.

#2 I have a mysterious disappearing coolant condition. It started as being hardly noticeable, but has lately gotten faster. about every 30 miles now, the overflow tank is empty and needs refilled. No water in oil, no steam/water out tailpipes, no smell of antifreeze, no noticeable leaks, no sound of burning off.

I have a theory, however. I think the problems may be tied together, may be a leaking intake manifold gasket? That would explain the rough running until warm (vacuum leak that seals) and the missing coolant.

Of course, there could be many other issues causing each of the problems (coolant temp. sensor, need of heated o2?, bad tps setting, etc.) any other ideas before I decide to just tear into it?

Update 6/15

Found two rubber caps, one on the intake, and one on the throttle body that were in poor condition, changed those. Tightened about 6 of the intake manifold bolts a 1/4 turn also. Results: Doesn't try to die on start, bucking sensation at lights until warm is much less noticeable, could just be the cam causing this. Now to tackle the coolant loss and newly developed squeaking belt.

 

Forgot to mention, no stored codes.

A while back, I would get an occasional code 34, but I haven't seen that for quite some time.

 

My guess is a blown head gasket. Pull the plugs...betting on #7. You should see a difference in the plug compared to the others. There is a test, not sure what it is called. But they pull the radiator cap and run the engine. If the head gasket is blown, you will find by products from the combustion in the coolant. kind of like putting a sniffer on the tail pipe. The distance on the gasket from the coolant hole to the cylinder on #7 and #8 is VERY SHORT.

Intake gaskets are usually oil related. Past experience on that one. And the blown head gasket......

How is coolant temp doing.....low coolant....higher temps....

 

coolant temps are great, constantly between 176-185 in 100 degree heat with the a/c on. If I ingnore the coolant loss problem for too long, I'll start seeing the coolant temps coming up towards the 190s. Obviously due to lack of coolant.

I just did the plugs, the only one that looked different was cylinder 6, wet with gas, spark plug wire had backed off. :o

I think the engine is just running too well for there to be a headgasket problem. Just changed the oil, no coolant in oil. Just did plugs too. No signs that indicate a headgasket, just trying to convince myself that isn't the problem.

I've always thought that a bad intake manifold gasket can cause a coolant leak, am I wrong here?

 

I just had my intake gaskets replaced because of a huge vacuum and coolant leak by # 7. I was thinking head gasket also, but was lucky enough for it to be the intake.

 

Some times when the coolant is left in the system for too long it simply looses its ability to not boil at the specified temperatures originally designed for. So, with the engines runniong at boiling temperatures the coolant simply boils out the catch tank while one is driving down the road. when you stop there is no real sign of any leaking unless you know where to look.
Adding more coolant does not raise the boiling level enough to stop the normal operating temperature boiling. Then is the time to drain, flush and add new.

Just a thought,

Gary

 

I'm guessing head gasket also. I think if you were losing that much coolant through an intake leak there would definitly be some sorta sign of it.

 

I looked around the intake today and noticed that behind the intake around the distributor looks a little wet, can't really tell though. I'm planning on having the mechanic look at it this weekend; I'll hope for the best, expect the worst.

 

I'm with the blown head gasket idea. I had a small head gasket leak that went almost unoticed for months. The only sign was dissapearing coolant from the resivoir tank. It finnaly gave out completely one day after a quick nitrous run. Smoke came out heavy from the exhaust and it started to overheat. I immediately shut it down and had it towed in. It wasnt until this point that coolant could be noticed in the cylinder, plugs, and oil. You could take an oil sample and send it to Blackstone Labs for analysis. They will send you the kit for free and the analysis is only $22. They should be able to detect if there is antifreeze in the oil. It may save you a tow in or engine damage.

http://www.blackstone-labs.com/

 

Update!

for the running rough at cold start up issue, I checked all vacuum lines around the intake. They all look good except a couple of ports that were capped off. The port in the pass. side of the trottle body had a cap on it that was shot, the end was almost completly ripped off, and a port on the intake manifold on the drivers side also had a cap in poor shape, just a little dry rotted. Changed both of those and the car runs a good bit smoother when cold.

It didn't die at first start and only tried when I first put it in gear, after that it was much improved.

Hopefully I'll learn more about the issue this weekend, still hoping for a leak around the intake manifold. Can't afford to replace this engine, so headgasket=

 

See new update on 1st post. Feeling a little better now, just hoping for no headgasket problems. Getting a compression check done towards the end of the week. I'll post the results.

 

I too thought I didn't have a leak, but disappearing coolant.
i found that little 5/16 air purge hose at the back of the block that is piped into the coolant/heater hoses was slightly cracked. only when it was shut off, and left to cool did it leak. Finally saw it when I let it sit for 2-3 minutes then moved te car..

 

Hmm...I'll have to check that. My guess is that I'm just worrying too much about something thats probably small. The engine has only been together for 2 years and about 15K miles, not ran at the track much, and not ran hard on the street. Its probably just a small coolant leak somewhere and not a perfect tune. I am only running a chip tune with all my mods, so that could be part of it...

 

Not sure that I'd consider losing the entire overflow tank every 30 miles a small leak. I'm thinking that's losing a serious amount of coolant. Personally, if I were losing that amount of coolant I probably wouldn't drive the car until I diagnosed it.

 

Well, those thirty miles are a little different than most. It takes me about a week of driving the car everyday to do 30 miles (city driving). In the amount of time I put 30 on my car, I could probably put 200 if it were highway, no stop and go every minute there.

Also, may have overestimated the leak a little. I've put 20 miles on it since the last time I filled it and haven't lost a drop that I can tell.

I let a mechanic check it out too. He said he "pumped up" the system for 10 minutes and didn't see any sign of loosing coolant.

In the end, maybe I'm just dumb.