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Thread: 2 Problems: Rough idle at cold start. Radiator fan not working when hot.

  1. #31
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    Quote Originally Posted by KMT View Post
    So this is the 91, then...been after you since 4.4.19 to replace the ECT...better late than never



    About that...too low, I think. You'll risk fighting the thermostat, running too cool, especially at speed when the fan is usually off, making it run rich, etc.

    As noted up thread, the stock fan speed strategy is as follows:
    Lo speed on: 222į
    Lo speed off: 214į
    -=-
    Hi speed on: 228į
    Hi speed off: 220į


    About the white smoke...remind me, did you get a combustion test kit to check for gases in the expansion tank yet? AZ rents them, I think. Anything but clean oil on the dipstick? Any foam inside the oil filler cap? Milkshake in the expansion tank? Upper hose tight but not bulging when the engine is at temp?
    Hello,

    It's probably good timing that I changed the ECT sensor in the 1991 because my 1990 (the daily driver) starts fine when cold, but gives me some difficulty starting if the engine is hot. I may replace the ECT sensor for the 1990 in the near future because this is a similar issue that my 1991 had back when it was my regular car (and I suspected the problems were related).

    The 1991 is not street legal (I just run it in the driveway), so I set the temp low (I can change it on a whim) so that I can test the wiring and thermostat I bought. When it's roadworthy, I will change it to be closer to the fan speed strategy you provided.

    I totally forgot to get a combustion test kit. That's officially my new priority now. I will check the other symptoms you mentioned as well.

    A part of me is upset that my headgaskets could have blown, but I've also owned this supercoupe since November 2012 and my other one since May 2015 and I haven't had to face this issue yet. I've been waiting for the "axe to drop" for years now. If it turns out my gaskets need replacing, I will be strangely relieved because if I take really good care of the new head gaskets, they should outlast the car. I will pamper these gaskets and never let the car overheat ever again. I also had a mechanic tell me that replacing the ECT sensor WITHOUT burping the system afterwards could have resulted in a tiny airbubble getting caught in the engine and blowing the gasket. I think my gaskets could have been on their last-leg anyways, but I'll definitely "burp" the system whenever I change the ECT sensor or Temp sending unit on the 1990.

    Thanks for your help

  2. #32
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    Quote Originally Posted by KMT View Post
    So this is the 91, then...been after you since 4.4.19 to replace the ECT...better late than never

    About the white smoke...remind me, did you get a combustion test kit to check for gases in the expansion tank yet? AZ rents them, I think. Anything but clean oil on the dipstick? Any foam inside the oil filler cap? Milkshake in the expansion tank? Upper hose tight but not bulging when the engine is at temp?
    Crap. I didn't know how the combustion test kit worked until after I had drained and removed the radiator (among other engine parts). My dad called our mechanic friend the day after my white smoke incident and he said that if my gaskets blew, we would need to drain the coolant as soon as possible. We've already removed the radiator and we have blown air through the engine to get as much coolant out as possible. The coolant is now collected in a giant Rubbermaid tub (the test kit appears to only work while the radiator is still in the car).

    At this rate, should I bolt back on the parts I removed (alternator, radiator, SUPERCHARGED tube, and a couple other upper things) and refill my radiator and purge it to do the test or should I just keep going and replace my head gaskets so I don't have to worry anymore. I'm pretty sure they were JUST STARTING to go out anyways, but I don't have any concrete proof other than a little white smoke out my exhaust and an unexplained loss of coolant (I've topped of my coolant overflow reservoir 2-3 times since my last overheating incident).

    Note: While my dad's mechanic friend and I were blowing air through the engine, some coolant was coming out of the radiator tube as a mist. I explained to the mechanic that the "mist" that was blowing out of the engine looked just like the "white smoke" coming out the exhaust the other day. It wasn't a thick opaque smoke, but rather just a white mist that lingers around for 5 seconds and dissipates. So I'm quite certain that coolant was coming out of my exhaust. A part of me doesn't want to refill the engine with coolant and run it again because if the gaskets ARE blown, I might damage something. However, if the gaskets are NOT blown (yet), I wouldn't know why coolant was coming out my exhaust. I will say that the white smoke happened coincidentally the same day I had replaced the Engine Coolant Temperature Sensor and I had not purged air from the system when I had done so. When I mentioned this to the mechanic friend, he said that failing to purge the air after replacing the ECT or the Temp sending unit could capture an air-bubble that could cause the head gaskets to fail (he used to own a Supercoupe, so he's familiar with some of the idiosyncrasies these cars have).

    I'm about to head back to the storage unit today, I'll check for "mayonnaise" on the inside of the overflow cap, and I'll check the oil dipstick and underside of the oil cap. I feel weird saying this, but I really hope my head gaskets failed so that when I replace them, I won't have to worry about them anymore.

    Thanks for your help; this is a real learning experience for me. Hopefully when my 1990 has a similar issue, I will be able to diagnose and treat it more efficiently (I'm planning on holding onto these cars for many years to come).

  3. #33
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    ..he said that if my gaskets blew, we would need to drain the coolant as soon as possible.
    If the oil on the dipstick is milky, sure, don't bother. But when it's not conclusive, testing for gases in the coolant helps being able to decide without simply jacking up the radiator cap and rolling a new car underneath it

    There are many ways to learn if there is an issue w/head gaskets, from reading plugs, to cooling system leakdown tests, to cylinder balance tests, to constant bubbles into the expansion tank, to ballooned/hard radiator hoses, how much history you have on the car, etc. etc. Some people go straight for the gaskets and others want to know more in case there are other issues that should be dealt with while the heads are off. Sounds like you've got plenty of advice and eyeballs now, so....

    Off hand it sounds like head gaskets, and/or cracked head, and/or leaking intake, but if it were my car, I'd want to know a bit more at this point. If the intake is letting coolant into the cylinders, you might not find combustion gases in the coolant, and wonder what the issue is if the head gaskets look fine. Maybe you caught the issue before it was bad enough to dump coolant into the oil...

    It wasn't a thick opaque smoke, but rather just a white mist that lingers around for 5 seconds and dissipates
    There's a fine line between routine vapor being burned off, and actual steam that might be seen as an early sign. A combustion test will help decide between those. Smoke, however, is unmistakable and there isn't much point in testing.

    Depending on the weather, any car that sits can see a bit of vapor/mist out of the exhaust when started from ambient moisture that has collected in the pipes/mufflers - tt won't hang around very long at all. White smoke that lingers is different, and a dead giveaway for failed gaskets. You might also see water on the ground directly under the tail pipes that doesn't seem to dry up as quickly as you'd normally expect. I wouldn't start ripping the engine down simply over a quick mist...
    Last edited by KMT; 06-21-2019 at 01:23 PM.

  4. #34
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    I feel like I perhaps should have done the combustion gas test, just for peace of mind and to perhaps narrow down what the problem could be if my head gaskets end up looking ok. Lots of parts have been removed (including power steering pulley/pump, Supercharger, both Tubes, and harmonic balancer pulley), so I think weíre marching onwards to replace head gaskets now. The overflow tank cap does not have ďmayonnaiseĒ in it and the oil cap underside looks ok. My oil is pretty clear because practically no miles were put on it since its last oil change, but I could examine it closer.

    I will say that the white smoke was big enough to be noticed from within the car (I briefly saw it in my rearview mirror). It was a warm, dry day and the car had been running until it was hot enough to send coolant to the radiator (my fan came on). So the car was close to normal operating temp when it happened. The car has been started and idled more than normally the past couple weeks, and it never spit out white smoke like this before, so it seemed really serious.

    In a few days, Iím going to order some parts (after the heads are removed). I was wondering what the best head gaskets for the 1991 SC 5-spd would be. Should I go with MLS head gaskets or are those only for the 1994/1995 SC? I also saw some people recommending Fel-Pro head gaskets.

  5. #35
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    I've only used Fel-Pro and had good luck. I also had my heads refinished to RA20 (a smoothness factor).

    Others can chime in on MLS gaskets, but they should be paired with ARP studs vs. bolts, and the block should be similarly machined, as I understand it. If you're going to significantly increase horsepower, MLS is the way to go.

    See: http://www.sccoa.com/forums/search.php?searchid=3077073
    Last edited by KMT; 06-22-2019 at 10:17 AM. Reason: added search link

  6. #36
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    Quote Originally Posted by KMT View Post
    I've only used Fel-Pro and had good luck. I also had my heads refinished to RA20 (a smoothness factor).

    Others can chime in on MLS gaskets, but they should be paired with ARP studs vs. bolts, and the block should be similarly machined, as I understand it. If you're going to significantly increase horsepower, MLS is the way to go.

    See: http://www.sccoa.com/forums/search.php?searchid=3077073
    I’m absolutely getting the ARP studs (already ordered). I’m leaning towards getting MLS gaskets. I’m keeping the car mostly stock, but I like knowing they could handle some extra performance mods, should I ever go that route.

    I removed both exhaust manifolds today. The drivers side was no problem but 2 bolts snapped off on the passenger side. Not sure what exactly to do about that yet, but I still need to remove the heads in the next couple days. In the picture included, you can see a little piece of one of the snapped off bolts (hopefully enough is sticking out to be removable).

    Edit: Crisis averted. I happened to have spare heads from a 1990 Supercoupe engine that I forgot about. My mechanic friend thinks they will work fine. I’ll hang onto my heads with the rusty bolts snapped off just in case there is a way to remove them when I have some spare time.
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    Last edited by Rick_Leuce; 06-23-2019 at 10:37 PM. Reason: I found spare heads.

  7. #37
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    A tree fell in my yard yesterday, so I didnít remove my heads today like I planned. Howevever, something just crossed my mind that I feel like I should share. When I bought my 1991 SC over 6 years ago, I think I remember the guy telling me he changed the head gaskets (I could be wrong). If thatís the case, Iím concerned he MIGHT have re-used the stock headbolts instead of buying new ones (the previous owner did some sketchy things to the car that Iíve had to undo over the years, so anything is possible). Wanting to lean on the side of caution, what would be the best thing I could do to minimize the possibility of snapping head bolts? PB blaster and a steady hand? Using a torque wrench so that I donít apply too much pressure removing them? Again, I canít remember for sure if the guy said he changed them (at over 130,000 miles, I assume he did) let alone if he re-used the original head bolts (you can look at the picture above), but Iím an amateur and thought it was better to ask a stupid question than possibly snap a bolt in my block.

  8. #38
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    TTY bolts are 'springy', meaning they can act funny when you try to remove them, especially by hand.

    Save yourself the struggle, use an impact to pull them, and don't worry about what someone may/may not have done during previous repairs.

  9. #39
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    Heads and head gaskets removed. My mechanic friend said that the heads on my 1991 (the one I snapped 2 rusty bolts in when removing the exhaust manifold) look better than the spare ones I found. He says we may have to drill out the two snapped bolts and re-use my 1991 heads.

    I tried to examine the old headgaskets that I removed from my engine. I can't tell for sure where it failed, but I noticed a little area where the gasket looked like it was tearing away from the metal ring. I don't know for sure if this happened when we removed the gaskets, but it looks like a soft area that could have been compromised and that became more obvious after pulling on it. There's also a thick, black tar-like blob stuck to the inside of the metal ring near where the tear is. What do you guys think?
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  10. #40
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    You've identified at least one fail, no doubt. I've got a used gasket that looks just like it

    What cylinder is that? Passenger side rear?

  11. #41
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    Quote Originally Posted by KMT View Post
    You've identified at least one fail, no doubt. I've got a used gasket that looks just like it

    What cylinder is that? Passenger side rear?
    I think it is the passenger side rear. Is that one particularly prone to failing?

    (I'm not at the unit now, so I rotated the photo to make it upright and I flipped the image horizontally so that the orientation of the channels that coolant flows through matched the ones of the engine).
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    Last edited by Rick_Leuce; 06-26-2019 at 12:44 PM.

  12. #42
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    Yes, pass. side rear is a very common location. Same thing I found on my '90.

    No coolant in the oil, but bubbles/gases in the expansion tank, and plugged cats.

  13. #43
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    The two rusty bolts that were snapped off in the passenger-side head have been removed. One of them had to be drilled out, so we will replace it with a stud (that is slightly larger than the old bolt) and secure it that way.

    I've removed as much of the old headgasket material off of the engine block as I could with a razor blade, brake cleaner, and a cloth rag. I've included a close-up of what it looks like (I left a little PB blaster in the cylinders to prevent rust). I saw a video where someone used a bristle disc and a fine Scotchbrite pad to clean off the engine surface, I was wondering if this would be ok as long as I follow-up with a straight edge and feeler gauge to make sure I didn't remove too much material.

    https://www.youtube.com/watch?v=Uy5p-cUge5s
    (skip to about 6 minutes in)

    I got FEL-PRO PermaTorqueMLS 9263 PT and 9262 PT Headgaskets. I know they have a specialized coating that is a little more accommodating than regular MLS gaskets, but I want to get the best flatness and finish I can (preferably without pulling the engine).
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  14. #44
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    Discussion here on using MLS without finishing the block surface: http://www.sccoa.com/forums/showthre...hing+the+block

    About using scotchpads...they contain microscopic aluminum shards and I don't recommend getting them near any engine parts, trans internals etc. You might not see them, but they can remain behind and act like little hacksaw blades. I would also avoid power discs, etc, too each to create small gouges/imperfections, etc. Block sanding w/fine grit is what the dealers used to do, I hear.

    The photos don't show any drama I can see right off...looks good from here - use your finger tips to feel for anything still attached, and clean up with alcohol when done.

    About replacing bolts w/studs, be sure they cooperate with items that might rely on them when reattached, such as the dipstick and heater hose retainers, also confirm the manifold can be reinstalled without needing to pull them back out.
    Last edited by KMT; 06-28-2019 at 02:36 PM.

  15. #45
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    Good evening


    With the heads off the car and on jack stands here are some suggestions to inspect and or replace I regretted not doing and or was instructed by a engine machine shop to be aware of.

    Upper Control Arms.

    TEVES reservoir hose to pump.

    Battery ground cable to driver side engine mount for corrosion.

    Clean and treat underneath battery tray areas for corrosion.

    Starter relay for cracks.

    Ignition switch.

    Heat sink compound underneath the DIS.

    Spark plugs and wires.

    Exhaust manifolds for evidence of leaking at the flange.

    If manual check condition of the clutch master cylinder reservoir fluid.

    Engine and transmission mounts.

    Power steering hoses, pump and rack.

    Radiator, oil cooler and heater hoses.

    Condenser cleaned and combed. Replace both sides of the foam weather seal facing the radiator.

    Repair or replace air dam.

    Clean the intercooler.

    Radiator professionally cleaned and pressure tested.

    Change the thermostat and water pump.

    Chase the thread holes on the cylinder head. Pay special attention to the threads for the valve covers, intake and exhaust manifold. Chase the thread holds on the intake manifold thermostat housing.

    Chase the engine block cylinder head bolts threaded holes.

    Inspect lifters, rocker arms and push rods for excessive wear. Replace if necessary.

    If needed change the tension pulleys from plastic to steel.

    If needed change the Supercharger, Jackshaft and Accessory belts.

    Check service of supercharger oil. Inspect supercharger snout for evidence of oil leakage.

    Change fuel filter.

    Change oxygen sensors.

    Inspect PCV system hoses and valve.

    If needed adjust oil pressure sender fitting (driver side of the engine block) to gain better access to sender when the power steering bracket is installed.

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