67 GS 400 is running way hot

[Shakadula]

I did pull the motor. Actually, not too bad but with just me, it is taking time. Finally got the gasket set and intake manifold gasket. I was surprised that the intake gasket is metal.

Anyway, I did a compression test (before I pulled the motor) and all is good and within spec so I am not going to pull the cyl or crank. I do want to clean out the oil and water passages and am looking for suggestions. I have a 150 PSI air compressor but am unsure of what to do at this point. Need help here.

Also, the heads. They seem pretty clean but since I have them off the motor, are there any suggestions on what I should do with them since I have them off the motor?

Last thing, I will be changing the color of the motor from Chevy orange to Buick RED.

Thanks in advance.

[DocModisett]

2 things will make a engine run hot most of the time.... poor circulation of coolant , or poor circulation of air thru the rad.... or both,,,, and ,,,, sometimes real late ign timing can do it.... make sure that the rad. is clean and free flowing,, and there is plenty of air coming thru it.... if you dont have a fan shroud , buy, build , or steal one and put it on.... or make sure the fan blade is within 1 in. of the rad. and multiple blades not just 4 ,,, at least 6 or 7..... and personally , I dont like clutches because they go bad and toss the fan thru the radiator... but they can cause over heating if they dont work right....I prefer to run either straight drive fan or electric fans.... set up right electrics have some advantages in city traffic.... to me,,, one would want a engine to have as much ''cushion'' temp. wise as possible,,,, not lower than 160 deg. but not very much over 200 either...Buick engines in the 50's thru 70's were designed to operate in that range.... nailheads, sbb's and bbb's.... so I go with ''old school '' ways and change thermostats in spring and fall...the way we used to do it.... 160 deg. in spring and 180 deg. in fall.... so the engine has a temp. ''cushion'' before it reaches the upper limits... if it wants to run cooler , it can......just some ideas

[sabrerattler7]

Something out of balance: like a torque converter, (I've had that) mis aligned or bent flex plate(I've had that) mis aligned bell housing ,hard to screw up but possibe. Ford had trouble on the Aerostar with factory machining alignment and replaced abunch of transmissions and some engine bearings.

[Robert Hare]

Go back to basics, the thermostat olny controls miminum operating temperature the maximun temperature is controlled by cooling water flow, radiator capacity, timeing(a retarted engine will run hot)and load on the engine

[Anomaly]

Double check the coolant that was put in the engine.... Dex-Cool and ethylene glycol antifreeze can NOT be mixed. Put in the same system they will form a sort of mud and clog the system... Most people don't know and just grab a jug of Dex Cool at the parts store by mistake...

[DocModisett]

Yup, what Robert says.......

[BigRivy]

Without completely disassembling the engine and hot tanking it there is really not much you can do to clean any of the oiling passages. You can remove the oil pan and clean it and the oil pickup but that's about it. You should have flushed the cooling system before you removed the heads. Now if you try to flush the block you are going to get water down into the rest of the engine where it does not need to be. With the block completely drained I would get a good light and look down into the water jackets through the holes in the deck and take a look. Is there a lot of sediment or other goop down in there? If there is you might try to get it flushed out. If there is not then don't worry about it. If your freeze plugs are original I would inspect them closely and change any that are corroded. It will never be easier to change them than when the motor is out and on the stand. You might pull the block drain plugs and clean out behind them also. You are kind of in a hard position. You have not pulled the engine down far enough to do any meaningful cleaning. If the water jackets don't look too bad I would put it back together and try to flush it while it's running. In all my years in the automotive business I have never seen a heating problem that I would blame on sediment in the block. It would have to be full almost to the deck to cause a problem. As far as your heads go you can take them to a machine shop to have them checked out or just clean the sealing surfaces up and bag them in plastic bags to keep them clean till your ready to re assemble. On further thought there is one oil passage that it might pay to investigate and clean. That is the one that brings oil to the rocker shafts. You will not be able to just run a bunch of pressurized air through it. Find it, the oil feed hole, on the deck of the block and run a wire down through it and see if it has a bunch of crap down in it. A small passage brush and some carb spray will help. Hopefully there is just an open hole with some oil in it but if there is a lot of sludge it pays to try to get it out. All of this assumes you are using the original block. After 1970 they started oiling the top end through the push rods and quit using this oil feed passage in the block. Clean the corresponding passage in the heads also. You can use compressed air on the passage in the heads as it's open on both ends, if the rocker shaft is off.

[Anomaly]

Cleaning oil passages? Sea-Foam, Sea-Foam, and Sea-Foam It's always worked well for me... however, on larger engines you may want to leave it in for awhile... 30-40 minutes....

[Shakadula51]

Seems the upper rad hose from NAPA was collapsing underheat. Put on a universal hose and the motor runs around 200 degrees in hot weather. Maybe 210 at idle. Anyway, motor is back in the car and running great. Now where is the warm weather

thanks everyone.

[Shakadula]

Car seems to be running well after all of that work and about 2000 miles. My sunpro gauge measuring the water temp was out of wack. I put in a new water temp gauge and that reads 190 degrees even at idle. i
I appreciate the thoughts on the rear main seal issue as I never thought sbout the torque converter. I will look into that.

Thanks everyone. Can't maintain this car without you.