The Stovebolt Site Forums The Shop Area Engine Shop Running to hot.

here what I have a 250 40 over with dish top pistons with a 194 head, 499 lift 268 cam, 650 double pump dual line 4 barrel carb, dual point dis. headers dual exhaust and M21 4 speed, 373 pos. The problem that I have is it wounts to run at 210 to 230 degrees at idle. put new water pump new raditor and 180 degrees ther. flushed system out with super flush. just started doing this after old raditor busted and put new raditor in. have two very big electric fans on the raditor. if I drive it it runs about 205 degrees. needed it down around 180 to 195 degrees so it will run it best. dyno tested a few years ago and at rear tire making 165HP and 202FTlb of torque in fourth gear. Not bad for a engine that was rebuild al most 15 years at time of dyno test. now the engine is 18 years old. check the compresson cold and it makes about 155 to 165 psi. the raditor is for a 1966 big block truck. looking for something to do to it.

are you sure the new rad is really clean and all tubes open? sure sounds like a problem w/ that if it was runnin at lower temp before you replaced the rad, unless something got into the block and plugged things up

Bill

I flushed the system out and added 20% antifreeze and 80% water and a bottle of overheat stop and that helped alittle and changed the t-stat to 160 degrees. running about 195 to 200 at idle. when doing burn outs it will go up to about 220 to 225 degrees. so getting better. has any one every cut the cross brace out in front of the rad, will it cause a problem. If I do this can put a fan in front of the rad to push more air at idle and while setting still.

If it ran OK a while back, it should run that way again. Given you didn't make other changes like timing, I would suspect some crap broke loose from you old radiator and found its way to the block. Now may be in the new radiator. I would take the radiator out and have it checked and flow tested. I would also flush the block.

You need a 50/50 mix of glycol (coolant) & water.
Too much of either & you'll run hot. Drain & fill the cooling system accordingly.

Jim Sgrig

Go borrow a hand heald (Lazer) thremometer and make sure it really is running hot. You can also check the radiator for hot spots or cold spots.

100% water is the most efficient coolant. Try it with some of the aftermarket "water wetter" additive.

Running hot at idle, which has no load on the engine, could mean your timing is off, radiator is not working, water pump is not working, or the fans are not working. Check the tune up first, then move to the radiator. Higher rpms of driving helps push water through a bad radiator, at idle there is not enough pressure to move it.
New water pump should be OK, and you can see and hear if the fans are doing there job.

Mine runs hot at the front of the head where the sensor is. At the back of the head and at the radiator, is 10* cooler. Just something about the design I guess.

Keep is posted on what you find, Joe.

I go with PieWagon on the 50/50 mix. Another thought... Have you checked the radiator cap. I had one go bad on an F-250 once, and it heated up terribly. Couldn't tell by just looking at it though. Good luck.

I have flush the whole system out two times, the only thing that is different is electric fans, did have a flex fan. have a bottle of water wetter i the system and it made about 5 degrees different. was told to day to open the headers up a run it to see if it changes any thing. the mufflers are about 15 years old. had 50/50 mix in there and it run hotter. will try the open headers in a few days and see what happens. thanks for helping.

What is the CFM rating of the electric fans? They rarely push as much air as a flex fan. Also, check to make sure your ignition timing and exhaust valve clearance is correct, both will make the engine run hot if wrong.

One thing most people overlook is a shroud,they will spend a lot of money on an electic pusher fan.Most of the cars and trucks I see at the shows have a big gap between the radiator and the fan.A shroud will force your fan to pull a lot more air thru the radiator.

The fans are pullers and the mount right on top of the rad and the cover all but the top two inches. don't know the cfm for sure. the fans are dual fan in one mount next to each other. I do know the pull about 9.5 amps a piece. the fans mount has a rubber strip around the body next to the rad. go to try the open headers and then try to put the flex fan back in to see what happens.

Joe h's recomendation is a good one. will the truck go ahead and boil water out if you just leave it sit and idle? If not theres a good posibality the gauge is reading wrong, because you have lost some ground if its an electric. if its a regular manual type gauge with a bulb look for capilary tube running too close to exhaust. Good idea to make absolutely sure you have a problem and its not just the gauge pulling your leg.

It a bulb type and the cap tube runs on the other side also the hot/cold factor switch under the stat will light the hot light when it get to 230 degrees. its does not boil the water out of the cap I cool it off before it gets that hot. got the cap off with it around 210 and the water flows great also. The cap is also new. hopefully I can try to put the flex fan back on Sunday and see what happens, the electric fans may just not be able to do the job. Thanks for all of the input. Danny super250six

This is a long shot but any chance they are wired backwards such that they are pushing?

Does the engine get hot right away or does it gradually get too hot? If the temperature steadily goes up to a certain spot and stays there, I would say your guage is inaccurate or something is regulating the temperature (like a bad thermostsat). If it slowly gets hot I would say it's a flow problem, like a partially plugged radiator. Possibly you could also be running too lean or have a headgasket out. I run a 350 in my truck with a radiator that would support a V-8 and it never gets up past half way on the guage, regardless of how hard it's pulling or how warm it is outside.
Scott

Update
open the headers today and run for about a hour and it try to run alittle hotter with them open. about 5 to 10 degrees hotter. soon as can going to put the flex fan back on and try that. will keep everybody updated. thanks again for the help.

I don't know for sure what the protocol is around this here shop but I'm posting in this string instead of starting a new one. Somebody'll square me away if I need it, I suppose!

Anyhow, I was/am having a similar problem as super250six with my 58 Apache (283 cid). Rebuilt engine, new water pump, new radiator, new thermostat, new sensor, hoses, etc. Same fan as before I pulled the engine. I don't have the exhaust bolted up beyond the headers.

Initially I'd start it up and it would idle for about 3-5 minutes and the temp gage would drive right up to max. (original gage so not a particularly precise instrument).

I set/re-checked the timing and went down thru the litany of troubleshooting suggestions posted in earlier this string. No joy. Still pegging the temp gage after idling a few minutes.

I pulled the newly installed thermostat and discovered that I had a 195 deg. thermostat - musta been boxed incorrectly or returned to the parts store or something. I swapped the 195 for a new 160 deg. thermostat and that definately helped some.

However, after about 15 - 20 minutes idling in my driveway, the gage went to the max again! While the engine is running up at idle I can watch the temp gage & see when the thermostat opens up (a bit past halfway on the gage). The gage drops, stablizes for awhile then starts rising again.

What else can I check? How do these temp sending units work? Should I buy a calibrated gage to hook to the sender & see what the temperature really is? Is there such an instrument? Can I test or calibrate the temp gage (it's the original)?

I'm going to drive it around the block tomorrow to see if the temp (or rather temp gage) stablizes at a lower level when moving or not. I expect it will but how's the booger gonna act in stop & go traffic?

Anyhow, I hope enuff folks are still wired to this string to help. I'd get mighty bent if I fried the new engine! Red58 might hear me screamin clear up in glacier valley!

A new engine will run hot till you get it broke in some. It shouldn't get this hot so fast though. When the themostat opens, does the full radiator get hot? Is it hot top to bottom and side to side? It sounds like a radiator problem to me. What does it do at a higher rpm? Try a few different things and get back to us, Joe.

one of the good thinks about a good ole stock 235, looks like most ideas have been covered,, did we mentioned timeing,,never had that problem but heard that it can cause it,, mine are usually simple, waterpump, hose, small leakes/low coolant,radiator,cap,thermostat, electric fan not working,,good luck with it and let us know what happen,,,,regards,,,Fred

This is a new engine? It is not that hard to incorrectly phase a cam and crank, especially with non-stock cams. Hope it is one of the easy things already mentioned though.

The old girl seems to be mellowing out some on her own. She still sits at the high end of the temp gage after idling for about 10 minutes or so but it seems to take longer to get there & I can drop the temp some by increasing the RPMs.

To JoeH & DennisM - yup, brand new rebuild.

I think maybe either the gage or the sending unit is somewhat off? The sending unit is new but that doesn't necessarily mean that it's working the way it should. I had somebody suggest that maybe the sending unit is screwed too far into the water channel on the manifold & because the sensor tip is too close to the metal it's picking up a higher temp than it should? Does that make any sense?

While I was out there goofing around holding a wrench & trying to look like a mechanic, I got to looking at my heater hoses. The more I looked at them, the more I started thinking that I may have hooked them up backwards. I can't find anything in the shop manual that identifies which hose goes where, so I'm gonna try for some adult supervision here in the forum!

Standing in front of the truck looking aft towards the firewall, here's the set up now:

The hose from the left outlet comes from the firewall, passes thru the heater valve and goes to the fitting on the manifold.

The hose on the right goes to the fitting on the water pump.

L R
(hose to manifold) (hose to pump)

Is this correct? If not, I have to change it but also would it have any bearing on the higher than normal water temp at idle?

Update:: changed the electric fan and put the flex fan on today and it runs at 160 to 180 at idle and up to 5000 rpm standing still with open headers. checking on the electric fans to see what cfm theyt are. looks like I needed bigger ones. will update more later. Danny super250six