Looking for evidence of coolant in an '84 Duke combustion chamber (Page 1/2)
David Hambleton SEP 25, 09:30 PM
My '84 Duke seems to be absorbing coolant; there are no leaks and none in the oil, so I thought maybe a head gasket issue...
I thought I would see white deposits on one of the plugs; #1 shows some fouling but not white. Any opinions?
Mike in Sydney SEP 25, 10:12 PM
From your post and from your pictures, I'd say you have a head gasket leak that allows coolant into the combustion chamber. The plugs are too clean for anything else. Really clean plugs usually signifies that coolant is getting into that cylinder and it is cleaning, steam cleaning the end of the spark plug.

How does the coolant look? Does it have oil in it? What about the oil? Does it look caramel coloured? Check under the oil filler cap for gooey, caramel coloured deposits.

Does the exhaust have a sweet scent? Are you getting more water vapour from the exhaust than can be explained by condensation?
Patrick SEP 25, 10:39 PM

Interesting that plug #1 has deposits on the ground electrode whereas the other three plugs don't.
theogre SEP 25, 11:41 PM
Head gasket that let coolant in a cyl would often let combustion gas out and can "Boil Over" very fast.

Intake gasket leaking is #4 cyl problem.

Your problem is #1 like Patrick said. Other three is OK.

But first test the coolant system under pressure w/ tester when engine is cold.
Most radiator tester won't fit on the radiator. Including most from "Loaner Tools" at AZ etc.
need a adapter... https://www.fiero.nl/forum/Forum2/HTML/145505.html Coolant Pressure Testing for Fiero.

Because small leaks often need working pressure to drip when you drive a quickly stops w/ engine off.
Look under the car for heater pipes and everywhere. Check P-side foor for leaking heater core.
Example: http://www.fiero.nl/forum/Forum2/HTML/146198.html Hidden Fuel and Coolant Leaks...

Back to iffy #1 plug... Can be the iffy plug, wire to it or dist cap.
#1 and less for #2 plugs and wires, they get more "water" on them because no air cleaner "neck" to shield from the engine vent and that alone often causes headaches.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

David Hambleton SEP 26, 08:18 PM
Thanks for the replies; 'looking for evidence' in the title has been satisfied.
It was reluctant to start after sitting a couple of weeks, but finally chugged to life on three cylinders.
I removed the #1 plug that showed some fouling in the previously shown pics; it was wet.
An inline spark indicator showed #1 was getting spark; switching #1 and #2 plugs still indicated #1 cylinder wasn't firing.
During various subsequent trials, coolant began spurting out from the exhaust manifold thru the joint cracks.
It seems like the fire suppression system spraying coolant into the combustion chamber was effectively preventing the fire.
I took a video of the dramatic behaviour, but I dunno if it can be loaded on here. Here's a pic:
theogre SEP 26, 09:16 PM
No spark then little pressure to fake "boil over" fast.
But can see enough vacuum to suck coolant thru bad head or head gasket.

Warning: coolant is very conductive and coolant on outside or at the tip of plug short out and won't fire.

Buy a cheap USB bore scope on amazon. Watch/record on Laptop etc. (May have apple happy unit too...)
Pull the plug.
look in the engine. Do Not run the starter.

Helps to use a coolant tester to push coolant thru leaks but many bore scopes are not water proof so don't get them wet w/ coolant. Likely start dripping very low pressure.

Some bore scopes have built in mirrors or other ways to look sideways.
Don't add mirror even came with because plug hole too small and loose them.

May not be a "bad gasket" but bad head bolt(s).
In either case... need head set and bolt set. Even if bolts look good many Dukes had problems w/ OE head bolts so Do Not reuse them.

If not that...
Can be bad head or even the block for 84.

Can try Pull the manifold and shield. Shield may have extra bolt at bottom. Shield may try to hide a bad head gasket or freeze plug.
David Hambleton SEP 26, 10:33 PM
Thanks for all the info Ogre.
The original engine in this 84 car had a head gasket fail at 77,000 km due to a broken head bolt by cylinder #4.
(The same thing happened to my 86 duke at 119,000 km at the same location.)
The original 84 engine was replaced under warranty at 102,000 km under the cracked block recall.
(It looked like a steam engine when it was running, but cloud production was the only evidence besides diminishing coolant level.)
The replacement engine now has 292,000 km on it and it's never needed other than routine maintenance.
I suspect the big leak that started today signifies a sudden additional deterioration of the already leaking head gasket.
The plan is to remove the head and see what the damage is.
The head bolts, head gasket and cracked exhaust manifold will be replaced at a minimum.

[This message has been edited by David Hambleton (edited 09-26-2022).]

theogre SEP 27, 06:10 PM
Engine Replaced?
Then may not be 84 engine but 85-86 w/ Roller Cam setup.
See my Cave, Duke Quick Ref

Most parts are same but have roller lifters on cam made for it and shorter push rods.
David Hambleton SEP 27, 10:05 PM
The original engine was replaced 28Mar1988 under recall campaign 8A05 'A' repair code 5 utilizing engine kit P/N 10101493.
There are several references to the 1986 service manual in the 8A05 'A' document; I presume disassembly will reveal roller lifters.
David Hambleton OCT 30, 08:40 PM
One little leak:


One steam cleaned piston: