The Stovebolt Site Forums The Shop Area Engine Shop Engine temperature increases at idle

The temperature seams to climb to 195 or even 210 at idle. When the RPMs increase the temperature drops to 180. When I shift into 3rd gear temperature begins to climb until RPMs increase. What's happening? The water pump is rebuilt.

My other engine seemed to be constant at 180. This is a rebuilt 216 bored over 40 thousandths of an inch.

Is the coolant boiling? If not, the engine is not overheating.
Jerry

Make sure you have the timing set as advanced as you can without pinging.

Does the engine have a thermostat installed? If so - and if it's working properly, then I suspect you might have a head gasket starting to leak.

No it's not boiling. So does that mean these engines run comfortably up to 210?

The thermostat is a 180 and I know it works because I put it in hot water and watched it open.

I would think whoever rebuilt the engine would have replaced the head gasket? Maybe I'll check the torque on all the headbolts.

Thanks.

It could be many things. To answer your question though, yes it won't hurt it to run at 210 - as long as it doesn't get much hotter than that. You may also want to consider that your temp gauge might not be accurate. Try measuring the temp with some other device like an infrared gun.

I had a similar problem with the 235 in my '50, however it was due mostly to a dirty radiator. Had lots of blocked tubes in it. I ended up putting an aftermarket aluminum radiator in it which solved the problem immediately, however my head gasket started to leak not long after that - I attribute that to the fact that it's 66 years old and spent 40 years sitting without any water in the block. I'm surprised I was able to drive it as much as I did before it started leaking, really.

We would need to know a little more about your cooling system before making an educated guess about what's going on. The Air Force term for that used to be a "SWAG" but that's not a forum friendly term- - - -the PC Patrol tends to get their knickers in a wad over that one!

Coolant boils slightly above 212 degrees F. at seal level unless it's pressurized. At 5,000 ft. altitude (Denver for instance) the boiling point drops to 205 or so. Every pound of pressure on a cooling system raises the boiling point 3 degrees, so the 7 lb. radiator cap that's pretty common on mid-1950's radiators takes the boiling point to 233 degrees. Modern cooling systems with high pressure radiators, heater cores, etc. can go to 15 PSI or more, with a boiling point above 250 degrees. Don't try this on a stovebolt, as the radiator core, or more likely the heater will explode.

A very clean stovebolt cooling system should rise to the thermostat opening point and stay there- - - -period! The temp might rise somewhat in traffic, or during prolonged periods of idling, or while pulling a heavy load up a long hill, etc. If you're experiencing temps above the stat setting, but less than boiling, something is restricting the coolant flow, the radiator or the engine water jacket is dirty, or a fan belt might be slipping, slowing down the water pump. It sounds like you've got a slightly dirty cooling system, or poor coolant circulation, or both.
Jerry

Thanks, this is very helpful. It sounds like the cooling passages of the new engine are clogged up a bit. The other engine stayed at 180 degrees and the only thing that has changed is the engine. Same rad, same water pump, same thermostat.

So I guess the block needs flushing. I understand this is done with a garden hose attached to the thermostat fitting and the rear petcock removed. Are additives recommended like vinegar or CLR or dishwasher soap etc...?

(It seems to me they should have cleaned the block when they rebuilt the engine).

There are two main cooling passage contaminants, and they respond to different treatments. I've never used CLR in a cooling system, but it's a good idea. I used technical grade Hydrochloric acid (muriatic) in the really rusty ones, 3 or 4 ounces of acid to a full fill of water and the thermostat removed. (no antifreeze) Run the engine with about half the radiator covered with cardboard to raise the operating temp. (Don't let it boil). Follow up with a fresh fill of water and a box of baking soda to neutralize the acid. Flush thoroughly and refill with a 50/50 water antifreeze mix.

For greasy crud, I use a can of drain-cleaning lye and water, plus 1/2 a cup of Tide. Circulate until hot, flush, and refill with water/antifreeze. Most commercial "radiator flush" products are far too weak to do any good. If the freeze plugs aren't new, be aware you might uncover some weak spots and cause seep leaks with this process.
Jerry

RPM's go down temp increases, RPM's go up temp decreases.

Is the fan belt tensioned correct? Belt loose fan slips and the water pump does not turn fast enough
at lower RPM's. Also verify correct size pulley is
on the crank and water pump and correct width fan
belt. Jeffrey

Good idea Jeffrey, my first thought was a loose belt so I tightened it, but the problem continued. It didn't occur to me to check the size of the pulleys and belt. Thanks.

Jerry, many thanks for the detailed instructions. Come spring I'll clean the system.

I drained the system, filled it with water and CLR, ran for 1/2 hr, drained again, filled with water and baking soda, ran for 1/2 hr, drained and filled with coolant.

Still no difference. Then I changed the cap from 4 lbs to zero pressure and it seems to be a little better. It doesn't seem to get any hotter than 190.

But still I don't see why it would fluctuate between 180 and 190. I wonder if a bunch of crud got flushed into the rad with the rebuilt engine? Maybe I'll remove the rad and have it flushed.

I run a 160 thermostat and 0 pressure radiator cap wih an overflow reservoir and my 49 216 stays on the "8" of 180 in the gauge spring, summer and fall. When I open up flow to the heater core in the winter it runs a little cooler, normally it stays on the "1" of 180 on the gauge.
It will climb alittle higher on extended idling and drop with more air flow through the radiator when moving, but never over the "0" of 180 on the gauge.

Try a 160 thermostat...

Someone has already said this, but try to advance the timing a bit. Slightly too slow or too fast on the timing can cause issues.

I just went through this! My 235 ran hotter when worked and cooled very very slowly if at all when idled. I had installed a new recored radiator, all new hoses and tstat and a new water pump. Previous owner let it sit with water in it! Although you have the opposite happening, I would recommend one thing to verify things!
First of all, do not trust a gauge! Try using a quality laser temp gun. You will be able to look at temps from front to rear of the head and out to the thermostat and radiator and also the return to the engine. This will give you an exact picture of just where the issue is.
My issue was plugged coolant ports at the head gasket and more rust build up in the head. As others have recommended, a good flush may do the trick too. There is a industrial coolant system flush called Thoro Flush by Irontite. It's a powder and can only be run in the engine for no longer then 12 minutes according to their directions. It's not cheap either, $15-$18. I tried it first and although it helped slightly I still ended up pulling the head and having the machine shop hot tank it and go through it. Just my two cents worth, some of these guys on here have incredible knowledge, don't be afraid to use it, good luck and let us know how it goes!
Troy

Here's an update. Good call on the plugged head.

I pulled the head today and sure enough the ports were plugged on number 5 and 6 cylinders. Here's the kicker. There was a mouse nest in the cooling system. In hindsight I should've flushed the engine before installing it since it had sit for many years.

Mouse nest