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I have a possible head gasket issue that I would like assistance in diagnosing.
1988 900 8-valve SOHC (non-turbo) 5 speed with 200K on the odometer . Head was turned in 1998 by a certified Saab mechanic. Coolant has been dropped or flushed yearly since then. Thermostat and thermo fan switch have long since been replaced with 82 degree versions. Radiator and water pump replaced within the last ten years.
Starting last year, I have had a strange problem that I now suspect is a slowly failing head gasket.
1) After sitting overnight, the car immediately starts and then dies. I have to restart it to give it gas. It runs like a tractor until I gun it and idle it at 2500 RPM for 30 seconds.
2) The car smooths out and runs great for the rest of the day.
3) If you let it sit for a long time after running it, it is once again rough at start, but again, it smooths out.
4) The temp gauge now runs slightly above half and it MOVES around, sometimes rapidly. Previous to this, the temperature gauge was stuck at about 1/3 after warm up and stayed there; it never got over half if even close. This is a new within the last year.
5) There are small champagne bubbles coming up the coolant hoses into the reservoir when the car is at temp and after the fan cycles. (Some say this is a tell tale sign of failing head gasket…)
Today, I was having my catalytic converter replaced. It was broken up inside and I thought perhaps this was the cause of the hard starting; too much back pressure. After the tech replaced the catalytic converter with a new Bosal, he started the car. It started hard and I saw two distinct white puffs of smoke come out the tailpipe. It ran rough for the first two minutes since he did not rev the engine.
He decided to do a sniff test on the coolant reservoir. He tried for twenty minutes to get a response but it came up clean.
Please note, in order to rule out other issues, I raided my long standing OEM supply of new spare parts. These spare parts are new (yes, brand new Bosch, Saab or OEM) and since last Fall: warm up regulator, cold start valve, Bougicord spark plug wires, NGK plugs, cap, rotor, hall effect sensor, fuel filter, both fuel pumps, new fuel lines to the injectors (braided steel), rebuilt fuel distributor as well as tested fuel injectors (I have four sets of used injectors and have test sprayed them and have the best ones installed in the car), new air filter, new oxygen sensor. Fuel line within fuel tank has been replaced (it was crumbled and there is a special type so that is also ok). Engine has been timed. Throttle body and butterfly valve have been cleaned meticulously. All vacuum lines are new or have been checked. Vacuum grommets on engine have been changed. The usual ground points have been cleaned and they are better than any I see on other Saabs.
When warm, this car runs like new with all of these new components. The goal was to fix this hard start issue. None of these items, changed one at a time, fixed this rough start issue. Today, the catalytic converter was changed out, and that did not solve this issue. When I saw the two puffs of white smoke, it seemed I might have the answer.
I have come to the conclusion that I must have a small coolant leak into one cylinder that causes the engine to run rough at startup until this is burned out of the cylinder. I had previously had the idea that one of the injectors was leaking gas after shut down, but after putting all four injectors into glass jars overnight, the most that ever came out was a drop or two of gas; nothing more.
I have not done a compression test since I don't have the equipment and I have been told that might not show up since the leak is probably quite small.
Anyone out there have any ideas of what might be causing this?
What is the gold standard to test for head gasket leaks?
Someone out there with an 8-valve must have seen this before.
I don't want to turn the head without a reason.
posted by 24.118.54...
, Fri, 1 Sep 2017 19:07:03, Tue, 22 Aug 2017 12:27:41
, Tue, 22 Aug 2017 20:16:25
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