Overheating on the freeway

[KustomSkylark]

I just recently got my car on the road since my 200 swap. Everything is pretty good except when I'm on the freeway, it heats up pretty quick. If i get off the freeway and drive surface streets, it goes back down. I did the timming without a light, could that be the problem?

 

[KustomSkylark]

oh and I back flushed the radiator and have a 205 thermostat

 

[MustangSix]

A car that runs at normal temps at low speed and idle, but heats up at high speed or high load could be the victim of one of several causes:

1. blocked airflow. there may be enough air passing thu the rad to handle the low demands of idle, but not enought to dissapate the heat of a higher load.

2. blocked water flow. The radiator coolant passages may be clogged and will need to be cleaned out. Again, enough heat capacity for idle, but not enogh for loads.

3. Blown head gasket. Same symptom. not a great problem at idle, but increased cylinder pressure will overheat the coolant at high speed.

4. stuck thermostat. a thermostat patially stuck open will flow enough water to cool at idle, but not at higher speeds.

5. not likely, but i have seen severly corroded pump impellers that have come apart.

 

[CZLN6]

Howdy KustonSkylark:

You would be wise to verify your initial advance timing with a timing light. Too advance or retarted ignition could cause the engine to heat too.

Adios, David

 

[KustomSkylark]

This is interesting

I'm pretty sure there isn't any blocked airflow, it's running with the hood off.

I'm not sure if it's the clogged coolent passages, the rad is fairly new but i did run it on my old engine that had a bunch of rust and debris in it. Do I need to take it into a shop to get cleaned?

I hope it's not the head gasket, I just put it together and had the head milled. Is there any easy way to tell if it is the head gasket?

im sure it's not the thermostat i tested that.

i'm sure it's not the water pump cause it's brand new.

So this narrows it down to the radiator or the head gasket. Does anyone have a source for a cheap 3-core radiator?

A car that runs at normal temps at low speed and idle, but heats up at high speed or high load could be the victim of one of several causes:

1. blocked airflow. there may be enough air passing thu the rad to handle the low demands of idle, but not enought to dissapate the heat of a higher load.

2. blocked water flow. The radiator coolant passages may be clogged and will need to be cleaned out. Again, enough heat capacity for idle, but not enogh for loads.

3. Blown head gasket. Same symptom. not a great problem at idle, but increased cylinder pressure will overheat the coolant at high speed.

4. stuck thermostat. a thermostat patially stuck open will flow enough water to cool at idle, but not at higher speeds.

5. not likely, but i have seen severly corroded pump impellers that have come apart.

 

[KustomSkylark]

oh and im going to time it with a light tonight to see if it's that.

 

[65coupei6]

Also check the lower radiator hose. At speed the lower hose can get sucked closed if it does not have the wire in it.

 

[ludwig]

Timing is very important. I had the same problem until I timed with a light and got it right on.

 

[PLP6400]

I had the same problem with my 65 Comet. It would only get hot at freeway speeds. The engine that I installed was a good running used engine. There was a lot of rust in the passages, so what I did was install my old radiator and flush out the engine. I thought it was clean and put in my new radiator. Within a few miles it was running hot at freeway speeds. I had to take the radiator out and have it cleaned. I then installed a Gano Filter in the upper radiator hose. The problem finaly went away but only after cleaning the Gano Filter several times

 

[Anonymous]

In addition to checking the initial timing, make sure that the advance mechanism is increasing the spark advance at higher rpm's. If the advance is not functioning, the spark is retarded to where it needs to be and the engine will overheat. So yes, timing could be an issue.

But, I suspect that you are overheating because the hood is not in place. I did the same thing after swapping an engine. I ran around town for a few days without a hood. The car overheated with the hood off the car. I did not have a cooling problem before with the old engine. When I put the hood in place the overheating disappeared. At the time, I thought like you are that the lack of the hood should trap less hot air under the hood. However, I think the lack of a hood disrupts the air flow through the radiator. Without the hood, the high pressured air is allowed to flow into the engine compartment and reduce airflow thru the radiator by equalizing the differential pressure. With the hood in place and the car in motion, you have low pressure scavenging effect under the car that helps pull air through the radiator.
So, put the hood on and watch the engine temp drop.
Doug

 

[nater200]

if you want any easy fix for a blown head gasket even if you don't you can do this it is pretty easy but it does take a couple days. go to your local auto parts store and look for a product called "BLOCK SEAL" it comes in a red can or a box. it is used to fix blown head gaskets i had a blown head gasket on my 1991 nissan pickup and i used that stuff and it worked like a charm it has been like a month and i haven't had a problem yet. the best thing is it only costs like 8 bucks and it works. just make sure you "READ THE DIRECTIONS THOROUGHLY".

 

[addo]

Except that anti-freeze digs that stuff right out again! You can't run any additives in your water with sealing products. Good fix to get back from a holiday, but not a permanent cure.

 

[Anonymous]

I got a 66 mustang, nearly a month ago now, I have noticed an over heating issue. Which I have narrowed down to 2-3 possibilities. Firstly there is no Fan Shroud. It only over heats when in traffic, so advice I have found on the net suggest this Fan Shroud will solve this issue. 2ndly there is a very small leak from the radiator, I doubt this is it but something I should address, i'm sure.. Someone advised me to buy (cant rem the name) something I put into the radiator as liquid and that it will fill the hole after harding.. My issue with that is could that substance continue into the engine or does anyone think its a bad/good idea.3rdly and again I doubt this is it.. but maybe the thermometer is broken.. (can't find the bloody thing though)
Any suggestion would be great.
Thanks in advance
Guys, by the way.. I am only new to engines and obviously the mustang.. so can you go easy with the technical explanation.. Thanks

 

[addo]

OK, first up one comment: Good idea to edit your profile "Location" and make it clear you're not in the US. Otherwise you'll get advised to just pick up something from NAPA, Pep Boys, Schmucks, Kragen, O'Reilly's etc...

You're stuck with some similar speed crimps to Australia. Besides the lack of a fan shroud, there seem to be certain speeds where airflow through the underbonnet is poor to non-existent. It's a function of the body design and turbulence generated. Chances are, that low speed limit is contributing to your heat issues.

The sender for your temperature gauge is located on the passenger side (if it's RHD) of the cylinder head, near the back. Look for something resembling a tiny spark plug with a wire plugged to the top of it. Experiment with the engine running, disconnect the wire and see if the gauge moves, then dead short the wire and see if the gauge moves.

It's not an accurate piece from the factory so don't trust it too far. You can be reasonably confident that it shouldn't go far past halfway when the engine is in good shape.

Be suspicious of the ignition system unless it's truly been gone through. Retarded spark can cause overheating, too.

The bad news about parts is that very few things are likely to interchange with local supplies. This will have you cursing as you dig deep at times for minor things, and other occasions, looking to local restorers/machinists for convenient and pragmatic resolutions. Can the radiator leak be soldered?

If it's duff, you might be looking at a three row copper/brass radiator from one of the Mustang specialists. You can run over USD$500 for an aluminium unit, but they're really made for a V-8 and there would be minor hitches to adapt it in.

Regards, Adam.

 

[CobraSix]

Generally speaking, if you are overheating at highway speeds only, it is either:

1) Timing
2) Lower Hose
3) Water Pump
4) Clogged radiator

That is in increasing order of price, so start at the top.

Check the lower hose and make sure it isn't spongy. If it is too spongy, replace it.

No matter how many times you flush your coolant system, if your radiator is rusted, you'll never get good cooling from it. I flushed my system 5 times (chemical) and still had problems until I replaced the radiator. Everytime I flushed, I would get more crap out of the radiator, so eventually I broke down and replaced it. Haven't had a cooling issue since.

 

[KustomSkylark]

Cool, thanks for all the replys. I've got a few things to try today after work now, I'll keep you guys posted.

Thanks again

 

[Guest]

Maybe do a compression test on each cylinder, to see if the head gasket is either bad or mistorqued. Ratings should be around or at least 100 psi, and variate around 5% from one cylinder to another. Also, I wouldnt run a 205 thermostat in summer. Im more of a 180 guy, sometimes even 160, but everybodys different.

My dad had a parts and machine shop for years, and sold thousands of thermostats over the years. It wasnt uncommon that a brand new thermostat ended up being bad and was returned for a new one.

Try buying a lower thermostat, and theyre so easy to change on these engines, its worth a try, two combos of possible fixes in one (with it being lower temp, and the original one could be bad). Be very careful to not overtighten the thermo housing or tighten one side more than the other when putting it together, they are made of the worst cast metal, much like a "Hot Wheels" car that you could crush with your toe.

You can also yank the radiator and blow out the fins with compressed air at a local repair shop, if you know someone that works at one. My father has a farm, where he drives over alot of leaves and grass, and regularly blows out the fins with compressed air on his cars/trucks. You can also do it with the radiator still in the car.

You can also buy an adaptor to blow air, and connect it to a local gas stations air pump, and just do it right there. I carry one in my trunk. If you choose to do this, blow from the inside of the engine compartment.

Best of luck,

Joe

 

[Guest]

To re-explain, maybe the radiator is clogged from the outside. Blowing it out from the OUTSIDE, anotherwards, blowing out the exterior of the radiator, could help. You may have debris from the old engine clogging it.

Back to work for me.

Joe

 

[Anonymous]

Corelon,
The small leak will be a cause of overheating, if you consider boiling over a symptom of overheating. Is your car actually overheating or are you looking at an inaccurate gauge.?

Anyway, a small weep is probably making the system operate at a lower pressure than designed. It would act like a system with a lower pressure cap or no cap at all. The system pressure is necessary to elevate the boiling point of the coolant mixture. If the boiling point of the coolant is elevated via a functioning radiator pressure cap, the heat capacity of the coolant increases, and it can transport more heat from the block to the radiator at a higher temp. The increased temperature can "drive" more heat into the radiator and increase the performance of the cooling system.
Doug

 

[KustomSkylark]

Last night I tried some stuff. First the timming was adavanced and I set it to TDC. Then I changed the bottom hose cause it didn't have the spring in it and felt kinda soft. I also put the hood back on. The car still got hot but then I noticed my coolent was kinda brown again, so it leads me to belive that I need to get the radiator cleaned out by a shop. But I'm also not sure if it's going into third gear. I'm running straight pipes so it's always loud and I'm not sure if it's stuck in second the whole time...that would make it run hotter. I posted in the drive train section about my shifting prob. http://fordsix.com/forum/viewtopic.php?t=24593