By on January 28, 2013

Paul writes:

Long time listener, first time caller. I have a 1982 Oldsmobile 98 Regency Brougham, that last summer I ripped the 307 out of. It now has a Chevy ZZ4 crate motor, backed by a TH 350 transmission. (Gasp! My hero!!! – SM)

My problem now is the car overheats if it is sitting still. I have a stock sized radiator (for the 307) installed, backed by a pair of electric 12″ fans. The fans are rotating in the proper direction, and do turn on and off properly.

My question now is: do I add more radiator (which would mean fabricating new mounts, lots of other stuff), or switch to a mechanical fan? I would need to go with a reverse rotation mechanical fan as I have the serpentine belt pulley kit on the motor. Do you think the fan alone will fix the problem? My other question is I only have about 1000 km on this engine, could it just be some trapped air in the coolant system?

Please reply quickly, as I am looking to start rolling in the car now that winter is done here in Winnipeg.

Thanks, Paul.

Sajeev answers:

First off, lemme say these vintage Olds 98s and Buick Electras are so much cooler than comparable Panthers. Second, OMG SON ZZ4 98 RESTOMOD FTW SON!

Now, how old is the radiator? You probably just need a new one, a OEM replacement. Radiators get clogged with age, and my first comment is to replace what you got if you do not know how old it is.

Once again, I love your restomod! Early 80s GM sedans deserve the attention you are giving. This is the real definition of Panther Love, fixing those often misloved American icons from our now unfortunate past.  But, now we have crossover utility vehicles.  So all the best to you.

Paul writes:

Hello Sajeev, thank you for the reply. The rad is brand new, installed at the same time as the engine. Any other ideas you have would help.

Thanks Again, Paul.

Sajeev answers:

How many CFMs (cubic feet per minute) do the fans push? You might want to see if they flow as well as the Lincoln Mark VIII electronic fan, as it is an upgrade for many vehicles, and maybe that’s what you need. See what CFMs it flows for sure.

Paul writes:

Hello Sajeev, the fans are not rated for CFM. I think I am going to go with the mechanical fan, and see what happens. I will make sure to update you with how well it works.

Thanks, Paul.

Sajeev concludes:

There’s nothing wrong with having a mechanical fan, but I’m starting to wonder if that isn’t the problem.  Yes, perhaps you didn’t “burp” the system properly and there’s an air bubble in it.  Definitely run the Olds (from a dead cold start) with the radiator cap removed and the heater on.  Let the system circulate and as it gets up to operating temperature, you should see bubbles escaping from the radiator. Top off the system right there, and in a minute or two, put the cap back on when it starts to dribble out the top of the radiator.**

Perhaps the radiator cap isn’t strong enough to keep correct pressure, or maybe the thermostat is defective…or maybe who knows from our vantage point!  But we all wish you luck on this unbelievably awesome restomod project. Dang.

 

**Not applicable on newer vehicles, as you can’t even see the radiator.  The same technique applies, but you have to remove the radiator cap from the remote fill reservoir instead. And maybe from another fill/bleed point, ALWAYS RTFM WHEN IN DOUBT!

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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40 Comments on “Piston Slap: Deffo Not Your Father’s Oldsmobile!...”


  • avatar
    Halftruth

    Water pump maybe? And are we talking a full blown, boil over or a temp gauge indication of an overheat? I ask as I had an 88 T-Bird that would warm up nicely and after about 15 minutes, the gauge would jump to the red on the temp gauge. After coolant flushes, numerous t-stats and a radiator I found that the gauge was wrong. Car never overheated. My .02..
    I am curious as to what you find Paul.

    • 0 avatar

      Ah, you are another victim of the retarded Internal Voltage Regulator found on analog gauges of the 1986-1988 Thunderbird and Cougar. I presume this happened more often when the headlights were on and you have the dashboard backlighting set on 100% bright.

      Cars, they are so much fun!

      • 0 avatar
        Halftruth

        As it turns out, yes. Strange thing.. After I found out it was the temp gauge, then the others started acting strangely as well. Not until I had spent the time and money to chase it did the others act up. Still a great car though, I enjoyed it.

    • 0 avatar
      fincar1

      I had a 1957 Plymouth Fury that was overheating per the temp. gauge. I finally simply checked the water temperature with a mercury thermometer from the lab where I worked…180 degrees Fahrenheit. I had suspected this because there were no other problems typically associated with overheating.

  • avatar
    PrincipalDan

    I’m jealous too.

    • 0 avatar
      Dukeboy01

      Me too. I’ve caught myself running searches on Autotrader and eBay for early- mid eighties full- size GM boxes lately. I’d be partial to a 2- door Caprice with a LS1 stuck between the framerails. It would be the perfect sleeper, with whitewalls, wire wheel covers, and a landau roof. If only I had time, money, garage space, mechanical ability…

      - Dave

  • avatar
    Feds

    How far off is your cooling capacity? Will running the heater prevent it from overheating? If so, an upgraded electric fan will probably do the trick. If not, give the cooling system a better once over: Are the fans coming on at the right temperature, is it holding pressure, is the waterpump good, etc.

    A tip: find an OEM electric fan instead of an aftermarket one. An OEM fan from a FWD/V8/Automatic will flow plenty of air for almost any application. Also try to concentrate the fans along the coolant path. i.e. if the rad flows from top left (hot) to bottom right (cold), place fans along the diagonal.

  • avatar
    jaydez

    Are the radiator fans the kind that just zip tie to the radiator or are they incorporated into a shroud that covers the entire radiator?

    Most radiators and the like that i have dealt with need the shroud in place so the fan pulls air through the entire radiator, not just the part with the fan on it. If you aren’t running a shroud around it, I would suggest fabricating one and incorporating the fan to the back of it.

  • avatar
    ZekeToronto

    ” … now that winter is done here in Winnipeg.”

    LOL–Did this request sit around a long time waiting to get published or have I missed a joke somewhere along the way?

    • 0 avatar
      prndlol

      Haha yeah, they’ve got a while to go yet in Winnipeg so my guess is this electronic letter got stuck in an internet tube.

      • 0 avatar

        Piston Slap has far more fans than it does weekly postings. It’s a sad reality.

      • 0 avatar
        ott

        Just what this guy needs… more fans!

      • 0 avatar
        Detroit-Iron

        Little known fact-the internet IS a series of tubes, more or less.

      • 0 avatar
        PrincipalDan

        Ten movies streaming across that, that Internet, and what happens to your own personal Internet? I just the other day got… an Internet was sent by my staff at 10 o’clock in the morning on Friday. I got it yesterday [Tuesday]. Why? Because it got tangled up with all these things going on the Internet commercially.
        […] They want to deliver vast amounts of information over the Internet. And again, the Internet is not something that you just dump something on. It’s not a big truck. It’s a series of tubes. And if you don’t understand, those tubes can be filled and if they are filled, when you put your message in, it gets in line and it’s going to be delayed by anyone that puts into that tube enormous amounts of material, enormous amounts of material. – Senator Ted Stevens (1923-2010)

      • 0 avatar
        CoreyDL

        +1 ott

  • avatar
    mfgreen40

    I dont think the radiator is the problem but this car was available with the infamous diesel engine which had a thicker radiator than the 307 and of course it would bolt right in.

  • avatar
    olddavid

    It appears our avocation is in good hands. What an imagination.

  • avatar
    danio3834

    Very cool swap. Great selection on the crate motor. I love me some GM B-body goodness as well having owned a Delta 88, box Caprice, Roadmaster and bubble Caprice in the past. (I still have the bubble, I can’t bring myself to part with a good condition un-donked last of the B-bodies).

    You very well could still have air pockets in the cooling system. You may find it helpful to raise the front of the vehicle a bit to ensure the rad cap is higher than the coolant in the lines and block while bleeding.

    The ZZ4 isn’t difficult to bleed like an LT1, it’s pretty much Gen 1 SBC with no fancy coolant crossovers or steam pipes. Pressure test the system and look carefully for even the smallest leaks. Small leaks can introduce pair pockets. If you’re sure you’ve got all the air out, it’s likely you still don’t have enough airflow over the rad at low speed.

    If there’s not enough shrouding around the rad or fans to create sufficient negative pressure behind the rad, this may result in reduced airflow. Other than that, you may just want to increase the rad capacity.

    I never had a problem with overheating with the ZZ4 I had in a 2nd gen Camaro with the stock rad, so you might want to try different fans first.

    • 0 avatar

      “You very well could still have air pockets in the cooling system. You may find it helpful to raise the front of the vehicle a bit to ensure the rad cap is higher than the coolant in the lines and block while bleeding.”

      Excellent advice. Thank you for sharing.

  • avatar
    dtremit

    “cooler than comparable Panthers”

    What does this phrase even mean? Is it like “more unique?”

    • 0 avatar

      They look better inside and out…cooler. If there was a significant performance difference (there might be) I would also mention that.

      • 0 avatar
        PrincipalDan

        Panthers only “win” because they stayed around longer. That says more about Ford and GM then the goodness of either one. I honestly wonder what the Fleetwood/Caprice/Roadmaster sales #s would have been if GM had just kept them in production after 1996 while investing the same amount in small upgrades that Ford did to the Panther platform.

        The other big advantage Ford has in my book is the quicker adoption of a good fuel injection system in 1985 combined with standard V8 from the beginning. GM didn’t adopt fuel injection until 1989 and then only on the 305 SBC and GM always forked around with the engine options depending on the year of production.

        Panther/B-body(&C &D) history is very fascinating to me from 1979 (when the Panthers debuted) until the death of the B/C/D in 1996.

      • 0 avatar
        dtremit

        I think you missed my sarcasm. Better than a Panther? Unthinkable!

        In seriousness, though, I’d give the cool factor to the C-bodies on the sedans, but to my mind the first-gen Panther coupes are a lot better looking than their GM equivalents. The Town Coupe roofline bests the similar formal look on the Olds, I’d say, and the Marquis coupe is nicer looking than the Electra.

  • avatar
    ponchoman49

    I bet a simple switch to the heavy duty radiator option (std with diesel) would solve this and it will bolt right in.

  • avatar
    pb35

    I misread the engine as a “Z24″ swap. I was like, what’s everyone so excited about?

    I have nothing else to add. Good luck getting it sorted, Paul.

  • avatar
    stuart

    With a new radiator, even one that’s a bit too small, I’m surprised that it overheats so easily. I would suspect a coolant flow issue.

    Before you change anything: 1) Is the engine really overheating? 2) Is the heat getting to the radiator?

    Get yourself one of those infrared thermometers with a laser (HomeDepot or equivalent) and find out really what temp everything is. With the engine idling hot, is the radiator also getting hot?

    With the cap off, engine idling and warm enough that the thermostat is open, do you see evidence of *vigorous* coolant flow in the radiator?

    In the distant past, I’ve had water pumps that slipped/dropped their impeller right after installation.

    Also: pull the thermostat and test it in a pot on the stove; start with cool water, heat the pot, and watch it with a trustworthy thermometer (your infrared one would do). Does the thermostat open promptly and fully at/above its rated temp?

  • avatar

    Having once swapped in an ’87 350 TPI/TH700-R4 into an ’89 Caprice wagon and having some cooling issues early on…I swapped in a four-core radiator and used an engine driven fan sticking halfway out of the fan shroud. I’d read that positioning (1/2 in the shroud, 1/2 out) was the best combo for efficient cooling.

    The gauge never got above 1/4 of the way up after that.

  • avatar
    Scoutdude

    If it overheats while idling but not when moving faster than 25mph or so then it is insufficient air flow from the fans.

  • avatar
    Moparman426W

    That is most likely his problem, he needs a 4 core radiator and pump driven fan. He could also install a pusher fan to go along with the engine driven fan. Dunno why he’s using a turbo 350, most people havn’t been using those in years. A 200R4 or 700R4 would give better acceleration off the line due to the lower first gear, and the overdrive top gear would give better gas mileage, plus both trannies are more durable than the TH350, and are dirt cheap just like the 350.

    • 0 avatar
      golden2husky

      I agree. The fact that he is ok when running but the temp creeps up at idle indicates to me insufficient air flow. I agree with the shroud, more CFM and then the 4 row unit.

      Moparman, remember all inherent overheating of Mopars from the early 70s? My Fury would overheat with the A/C on in traffic from the day of first delivery (I knew the original owner). When I got the car it had a flex fan. I changed to the biggest clutch fan I could find from a 440 car in the junkyard, added a new clutch, installed a four row custom made radiator, a waterpump with a special cover on the impeller, a good shroud and it still overheated in traffic with the air on. Then one day the clutch fan got stuck in the fully locked position. Bam, overheating done. Of course that killed mileage but for a couple of weeks it solved the problem. Everybody I knew with these cars had overheating issues and radiators that corroded through in a few years…never got to the bottom of that…

      • 0 avatar
        Moparman426W

        Insufficient cooling capacity can also cause overheating at low speeds and at idle. C The fact that your car stopped overheating after the fan locked up indicates that it wasn’t spinning fast enough when it needed to before to keep the engine cool. Never had a cooling issue with any of my mopars, they had some of the most efficient cooling systems out there. The big blocks are about the coolest running big blocks there are.
        The radiator in my oldest mopar, my 63 Imperial lasted until 1991 before I had to have it recored. My next oldest mopars are a 72 Imperial, 77 half ton 4×4 and a 78 New Yorker Brougham. They all went 2+ decades before the radiators needed recored. It makes a difference when you replace the coolant at least once every 2-3 years.

  • avatar
    greaseyknight

    The advise to upgrade the fans/shroud are on the right track IMHO, the popular OEM/junkyard route is one from a Taurus, if they can be found….

    The other thing to check is if the motor is running lean, or the timing is off. Both of which will cause the motor to run hot, that said my bet is still that it doesn’t have enough airflow over the rad at idle.

  • avatar
    28-Cars-Later

    A picture is worth a thousand words, pictures please!

  • avatar
    dudefromthenorth

    When you put in the zz4 block, did you keep the old Oldmobile fan? I think the ZZ4 drives the water pump in the opposite direction ….

  • avatar
    dudefromthenorth

    Oh never mind, ignore my previous post.

  • avatar

    I’ve never heard “Deffo” before; is that British? :P

  • avatar
    jacob_coulter

    If the electric fans are your only fans, there’s your problem.

    The 12″ universal ones you can get in parts stores are junk, if you’re dead set on electric, find an OEM setup from a Lincoln Mark Viii or Taurus. Those actually have the power to cool something like a V8. You might though have to upgrade your alternator.

    Personally, I’d go with a mechanical fan, heavy duty clutch and factory shroud. The hp savings for going to an electric fan are minimal and mainly at high rpm. I’d also throw in a 180 degree thermostat if it doesn’t have it already.

  • avatar
    Dimwit

    Another thing is go to Jay Leno’s Garage and look for Cooling. I saw a guy on there that made OEM fitment rads that had 30% more cooling capacity just for restomods. He was in the upper US somewhere.

  • avatar
    doctor olds

    I just stumbled on this page after being out of town when it was posted. Great car! I loved driving these around as a District Service Manager for Olds in the ’70′s and early ’80′s. We called them “deep rides” in the day. Always thought I would have a coupe after I left the field- still look for them. I love the engine swap- 307′s were gutless! My own choice today would be a 5.3L with trans from a late model pickup truck. Cost effective and fine performance.

    Fan shrouds are very important to cooling. If there is no shroud, that may be the biggest problem. It may be necessary to get a better electric fan setup with a shroud that comes very close to the tips of the fan blades. We had cooling problems with the 403 V8 in the ’77 Toronado. Toronados always had cooling challenges. It had a venturi ring that was positioned very close to the fan blade tips to substantially improved air flow through the radiator.


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