Cooling problems

[tlo86]

Take no offense in stating the obvious, but has the cooling system been pressure flushed and refilled with brand spanking new toyota red coolant and distilled water?

If not, it could be that the coolant is just old and broken down... it can't stabilize the water anymore.

:biglaugh: what why would someone want to flush and refill their coolant!!

ive seen swaps that still use the milky oil/coolant solution left in their radiators :3d_frown:

 

[jetjock]

I didn't realize water was so unstable

 

[jdub]

I'm with JJ...if the coolant gauge is showing normal with no stat, there is something wrong...it should show lower than normal temps. The radiator is the likely culprit. The boiling could be a result of this too, especially if the coolant mix is close to 100% water (lower boiling point).

Running with no thermostat causing an overheat due to coolant flowing through the system "too fast" is one of those myths you hear. If an overheat occurs with no stat, the problem lies elsewhere.

Running with no thermostat is not a good thing to do...the ECU stays in warm-up enrichment till 176 deg F...the ECU pulls timing at temps above ~210 deg F. On a fully functioning coolant system, the excess cooling capacity can keep temps below this, especially with low OAT's. The stat keeps temps in the range the ECU is looking for.

My next coolant change is going to be a through flush followed with a HOAT G-05 coolant fill.

 

[Facime]

Running with no thermostat causing an overheat due to coolant flowing through the system "too fast" is one of those myths you hear.

Thanks for dispelling that for me. Ive never tried to go without a t-stat but its amazing how some of these myths can stay with you. I was told that one by an old stock car racer in the 80's. Its amazing how influential an "old mechanic" can be sometimes.

 

[Firechikin68]

Nevermind guys. I used a block tester and I do have a blown head gasket. Thanks for the help.

 

[HommerSimpson]

I was told this a long time ago from a competent mechanic, but if its not true someone can dispel the info. I was told that having no thermostat can actually lead to overheating. The theory is that the coolant travels through the system so fast (as its not restricted by the t-stat) that it doesnt get a chance to cool as much while passing through the radiator.

Depending on the car ...system and all YES it can flow so fast it does not have time to cool down before it re enters the engine.. I have PERSONALY seen this many many times..
Real race cars use a washer instead of thermostate and they come in all dif sizes.. from very small to very big holes in middle... just for this reason... to slow down the flow enought to let the rad do its job...

 

[IJ.]

15+ years of leaves and crap blocking the Core and the AC condensor don't help either.

 

[jdub]

Depending on the car ...system and all YES it can flow so fast it does not have time to cool down before it re enters the engine.. I have PERSONALY seen this many many times..
Real race cars use a washer instead of thermostate and they come in all dif sizes.. from very small to very big holes in middle... just for this reason... to slow down the flow enought to let the rad do its job...

You know Hommer, sometimes "old school" works against you

First, we are not talking about race cars. What's done on a race car is not necessarily a good thing for a street car.

Second, this "myth" came from years ago when cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. This led many to believe that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. Cars built in the past thirty years use cross flow radiators (like the Mk III) that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it.

Third, the cooling system is a closed loop. That means the coolant spends the same time in the motor as it does the radiator once the thermostat is open or all the time with no thermostat. Using a restrictor to keep the coolant in the radiator longer to allow it to cool will also allow it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the radiator at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures in the engine.

I'm an old dog too Hommer (older than you) and I promise the old saying is wrong...you can learn new tricks

 

[Firechikin68]

You know Hommer, sometimes "old school" works against you

First, we are not talking about race cars. What's done on a race car is not necessarily a good thing for a street car.

Second, this "myth" came from years ago when cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. This led many to believe that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. Cars built in the past thirty years use cross flow radiators (like the Mk III) that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it.

Third, the cooling system is a closed loop. That means the coolant spends the same time in the motor as it does the radiator once the thermostat is open or all the time with no thermostat. Using a restrictor to keep the coolant in the radiator longer to allow it to cool will also allow it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the radiator at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures in the engine.

I'm an old dog too Hommer (older than you) and I promise the old saying is wrong...you can learn new tricks

Thank you for this response. A buddy of mine and I have been arguing over this subject for a few months now. This explains it all in good detail. Thanks.

 

[CustomOHioSupra]

heard this too many times....it flows too fast so it overheats.....(or gets hot spots because the flow has increased in one area while casuing a decrease in flow in another area )

i don't believe it....but maybe there is one car out there that can avoid hot spots with the restiction the thermostat puts on the flow

 

[CyFi6]

Second, this "myth" came from years ago when cars used low pressure radiator caps with upright-style radiators.

Cars built in the past thirty years use cross flow radiators (like the Mk III) that position the radiator cap on the low pressure (suction) side of the system.

What is an upright style radiator? And does crossflow purely mean that the cap is on the "low pressure" side of the system? I thought there were only crossflow and downlflow radiators and downflow had the tanks on the top/bottom and crossflow had tanks on either side purely for space/hood line concerns. And if i were right in saying this, doesnt our system have a downflow radiator?

Actually, upon further inspection of this picture it still looks like the radiator cap is on the higher "pressure" side, and not on the suction side. Please clear this up for me as i am not understanding properly.

edit: I think what is confusing me is, what is making this "pressure" Since the water pump is not positive displacement, it doesnt create pressure other than some kind of restriction to flow, and im thinking of the radiator as a restriction to flow, so as the water is being forced into the radiator there would be positive pressure in the upper tank (radiator cap). When in actuality you are saying that the thermostat is the only restriction therefore the cap is on the suction side, am i correct to say that?

 

[jdub]

The term "upright radiator" applies to what was used on cars 30 years ago...in reality, they are all "upright"

The terminology I used is a matter of semantics...by "cross flow" the coolant enters on the upper right and exits on the lower left. Technically, it is a downflow type with cross flow characteristics.

Take a look at the pic. The water pump shows "from radiator"...this is the suction side of the pump. The thermostat remains closed till coolant hits the specified temp and coolant is "pulled" through the radiator. It is on the suction side. The radiator is a restriction, but not nearly as much as the thermostat.

 

[CyFi6]

The term "upright radiator" applies to what was used on cars 30 years ago...in reality, they are all "upright"

The terminology I used is a matter of semantics...by "cross flow" the coolant enters on the upper right and exits on the lower left. Technically, it is a downflow type with cross flow characteristics.

Take a look at the pic. The water pump shows "from radiator"...this is the suction side of the pump. The thermostat remains closed till coolant hits the specified temp and coolant is "pulled" through the radiator. It is on the suction side. The radiator is a restriction, but not nearly as much as the thermostat.

Ah, this makes sense, thanks for the clarification.

Something unrelated, i have actually seen a picture long ago of the flow of a particular radiator where there were actually like 3 sections in one radiator. On the top left, it travels all the way across horizontally, then it turns back around, and goes in the other direction across the center of the radiator, then turns around finally for the last section of the radiator and exits. So in total the coolant will have crossed the radiator a total of 3 times before exiting rather than all of it flowing strait across. Have you ever head of this? And what applications does it have?
Actually here is something very similar to what im thinking of, but rather than having 3 rows this has two. Do they use this type of thing in production cars?
http://www.macsradiator.com/browseproducts/Aluminum-crossflow-radiator.HTML

 

[jdub]

Yes, I've seen those on muscle cars...I have not actually used one though. Essentially, it's two smaller radiators stacked on top of each other...it should be more efficient, but I don't have personal experience. I can't say I've seen a multi-pass radiator on a production car.

Keep in mind the stock system on the Mk III already has excess thermal capacity if the radiator is in good shape...the extra heat produced from moderate HP increases is no problem. Aftermarket dual core radiators for our cars is a significant jump in capacity and can handle just about any amount of heat the motor can produce. I really don't think the additional cost for the type radiator you're talking about is worth it.

What is worth it is to run the proper temp thermostat and keep the system as clean as possible...a flush/change every two years will go a long way. Take a look a JJ's coolant filter thread...a filter keeps the radiator healthy and efficient. Lower cost...works better...I like it

 

[Facime]

Using a restrictor to keep the coolant in the radiator longer to allow it to cool will also allow it to stay in the engine longer, which increases coolant temperatures.

That right there makes perfect sense and completely dispels the myth for me.

PS. like I said before it was an old stock car driver that told me that, he said they also used to take half the impeller fins off the water pumps as well. Just goes to show how things change.

 

[gtsfirefighter]

Nevermind guys. I used a block tester and I do have a blown head gasket. Thanks for the help.

This would be a good time to do a rebuild. If you don't you'll get visited by Rod Knock. You don't know how long that car was run on a BHG before you got it so the bearings are probably on their way out too.


Listen to Jetjock and get a new radiator to go with your new engine. I did. He's one of the few people here who bought his car brand new so DON'T take his advice with a grain of salt. In other words, he knows what he's talkin 'bout.