89 RENIX operating temp?

[Ecomike]

That is a great link you found!!!!!

I have always suspected this, but the magnitude he suggests is more than I ever expected. But I guess with a high rpm, HD water pump and partially blocked radiator it is possible!!!!

• Crossflow radiators with a fill cap always have the cap on the outlet side. Upright radiators have the cap in the inlet side and thus subject the filler cap to the pressure drop of the radiator's core in addition to the system pressure. This can lower the effective pressure of a 22 PSI cap to as low as 10 PSI.
• Thermostat housing restrictors were useful when upright radiators were used with 7 lb. caps. The restrictor slowed the flow and kept the pressure in the radiator down. This prevented the cap from expelling water and causing the car to overheat. Most people wrongly assumed the car ran hot and expelled water. The cars actually expelled water and ran hot.

The HO radiators have the cap on the outlet side! The Renix Bottle cap is on the pump outlet side!!!!!!! So high RPM, HD pump, partial blocked tubes in the radiator would be too much for the 16 lb bottle cap once the bottle runs out of air!!!!

More interesting comments he made:

• The system achieves this pressure only when the system is filled cold. When a warm system is opened and resealed this pressure is not obtainable because the coolant and trapped air are already expanded when the system is sealed.
• A Schrader valve installed in the system will allow the system to be charged by an air hose. This allows an already warm system to achieve operating pressure and minimizes the effect of trapped air in a cold system.
• The fill cap must be the highest point of the system. Surge tanks must be used if the top of the radiator is not the highest point.
• Trapped air seeks the highest point. A new system always has trapped air.
  Always fill the surge tank completely, when the system reaches operating temperature it will expel any excess water out the overflow.
• Placing a fill cap in the top radiator hose subjects the cap to the pressure drop of the top hose and the radiator core in addition to the system pressure. This can lower the effective pressure of a 22 PSI cap to as low as 2 PSI.

His last comment is poorly worded. He is trying to say that the pressure drop across the core, and the suction/pressure sides of the pump, create a low pressure and high pressure side to the coolant system, that in extreme cases can reach 2 psi on the pump suction side and 20 psi on the pump outlet side (which is the Upper Rad hose side). By extreme, I would think it would take a HP water pump, a nearly blocked radiator (or very undersized relative to the pump), and very high engine rpms.

 

[Ecomike]

This I did not know, and it explains why coolant can flash from liquid to gas as it exits the block, but be liquid inside the block:

Following is a typical Winston Cup engine at 100 GPM:

Lower radiator hose = 1.5 PSI
Block and cylinder head - each (at 50 GPM) = 8.5
Outlet manifolding = 1.25
Top radiator hose = 2.25
Radiator = 1.5
Total = 15.00 PSI

The pump must supply 8.5 PSI minimum just for the pressure drop across the block, before it ever reaches the radiator. I never realized the pressure drop was that high!!!! That helps explain the collapsing lower radiator hose issues (spring in the hose, in older hoses). Also explains exploding radiator tanks and upper hoses on the inlet side of radiators, when the flow through the radiator drops low enough, it spikes the upper hose pressure well over 20 psi, with out opening the low side radiator cap!!!! BOOM!!!! Failing, stuck-suddenly unstuck T-stats could add a water hammer effect as well!

Very interesting!!!!!!

 

[nickguy]

I thought it was interesting stuff too. Thanks as always Mike for your thoughtful posts. I do need to be careful not to overfill the bottle/aluminum and I am obtaining a couple of really high pressure moroso caps...and I like the idea of sealing two of them. Am also wondering if I should modify the radiator to get rid of the filler neck... I will post on my progress when I get back to the Jeep.

 

[Ecomike]

If you have a radiator cap on the cold side of the radiator itself, I would eliminate the inline filler neck entirely, as it is just not needed, and could be causing you headaches!!!!

 

[cruiser54]

I'm gonna throw a fly in the ointment here. All this scientific pontificating and I'll tell ya what I have. Two Renix Jeeps at 5000 foot elevation in Arizona. Factory thermostats # 83501426. One has a 2 year old radiator and the other I have no idea about. I run a Napa coolant bottle on each with the Napa 703-1396 cap. I have NEVER had to bleed a Renix cooling system either on my own rigs or at the dealership where I was Service Manager and Shop Foreman for 13 years. I use the stock fan clutches. Our temp here can range from 0* in winter to over 100* in summer. My Jeeps both run 200* to 205* consistently year round.

 

[Ecomike]

Hmm, let me get my fly swapper out.

LOL

 

[nickguy]

I'm gonna throw a fly in the ointment here. All this scientific pontificating and I'll tell ya what I have. Two Renix Jeeps at 5000 foot elevation in Arizona. Factory thermostats # 83501426. One has a 2 year old radiator and the other I have no idea about. I run a Napa coolant bottle on each with the Napa 703-1396 cap. I have NEVER had to bleed a Renix cooling system either on my own rigs or at the dealership where I was Service Manager and Shop Foreman for 13 years. I use the stock fan clutches. Our temp here can range from 0* in winter to over 100* in summer. My Jeeps both run 200* to 205* consistently year round.

My whole point is that the cooling systems are great and will compensate for other block or head perhaps too well. I actually makes overheating problems more difficult to troubleshoot or fix because you can work around it by gussying up the cooling system My previous engine was like yours... never had a problem and I did anything except change the belt.

Glad both your Jeeps run well. When they develop problems I have ointment.

 

[8Mud]

I#ve been working with heat exchangers of one flavor or another most of my adult life (well over forty years). And there is a lot more going on than one would think.

And there are even a few things I have never really figured out. Like why dry air cools better than humid air, but rain cools better than humid air or dry air. Or so it seems to me, empirical observation, no kind of measurements used, except the temp gauge in the cluster.

 

[nickguy]

Not really what I am seeing but some interesting notes from where it is hotter than Hades. Go Jeep also put in a Hesco hi flow pump. Still do not have my Jeep back but am researching a bit. Low pressure in the block actually can limit the heat transfer. Kind of counterpoint to having high flow radiators, thermostats and water pumps.

http://www.go.jeep-xj.info/HowtoRadiatorRestrictor.htm

 

[Ecomike]

There are many competing forces involved, and many of them vary in non-linear manners, and vary at different rates. So a little more flow at one fixed set of conditions may be good, and may be better than a little more pressure, but at another fixed set of conditions, the opposite may be true.

"Low pressure in the block actually can limit the heat transfer"

It does not always limit heat transfer, but if one is near the boiling point, it can cause flow issues, and severe heat transfer drops if you get localized boiling (or a certain area is not getting good coolant flow, then overheats locally and boils). In that case more pressure can stop the boiling, or fixing the flow problem can stop the boiling, and then "not limit heat transfer".

 

[sjx40250]

I was having overheating problems for a period of time. Replaced everthing! Minor improvement. In fact the only way I could get it close to behaving acceptably was to run without anti-freeze (better heat transfer without). I was on the edge. I know it was not the radiator (cored it with 30% blockage), new fan clutch, new hoses, new high flow thermostat (measured actual openings of a bunch of different ones), new water bottle and cap, new heater valve and new water pump. Did I forget anything? There was nothing left but the engine.

I was blowing a lot of oil into the air cleaner and decided to to a head job. I also replaced the rings while I was at it and upgraded to a FlowKool pump. that was 160K miles ago and it it runs like it did when it was new. I suspect something in the head was causing the problem but don't have root cause. I have since replace a couple of fan clutches and water bottles with new caps. No problems.

That is my cooling expereince with my 1990 Laredo purchased new in May of that year.

 

[Ecomike]

I was having overheating problems for a period of time. Replaced everthing! Minor improvement. In fact the only way I could get it close to behaving acceptably was to run without anti-freeze (better heat transfer without). I was on the edge. I know it was not the radiator (cored it with 30% blockage), new fan clutch, new hoses, new high flow thermostat (measured actual openings of a bunch of different ones), new water bottle and cap, new heater valve and new water pump. Did I forget anything? There was nothing left but the engine.

I was blowing a lot of oil into the air cleaner and decided to to a head job. I also replaced the rings while I was at it and upgraded to a FlowKool pump. that was 160K miles ago and it it runs like it did when it was new. I suspect something in the head was causing the problem but don't have root cause. I have since replace a couple of fan clutches and water bottles with new caps. No problems.

That is my cooling expereince with my 1990 Laredo purchased new in May of that year.

Getting oil on the filter could have been a CCV tubing-hose problem, and oil on the filter could have made the engine run lean. An exhaust leak, loose donut flange, or cracked header or leaking manifold gasket blowing on the block is often overlooked as a cause.

 

[sjx40250]

I did clean the CCV system and replaced parts without a change in the cooling problem. As it turned out, the head did need cleaning up, the seats in particular were on the edge as well as a number of valve guides which were contributing to the oil discharge.

Modifications since included a Borla header and exhaust and replacement injectors. This combination cause a configuration that did not allow emission passage. I ended up putting Split Fires in to get it to pass. With stock plugs, the cross over between too much NOx and CO was above the limit for passage. Good thing I had an adjustable MAP to tune it in!

 

[Ecomike]

Interesting. Was it just the split fires, or the adj MAP as a well that you got into compliance?

I have seen several reported emission failures here that seemed to be caused by non OEM headers. Most were NOx issues.

 

[nickguy]

Update on my rig...

Put my 195* RobertShaw thermostat back in and a spring in my lower hose along with a Hesco flowed tstat housing. Also took out the t out of the top radiator hose and replaced the cap on the radiator with a 25lb unit. First outing no heating issues at all or leakage. I no longer have spikes when I go uphill at high speed. what I do see is that it will spike from approx 200 to 210 and then stay there after an uphill charge on the freeway. I think that it might be good to have a spring if you have a high flow pump like I do. Am tabling rebuilding the head for now.

 

[Ecomike]

I have never seem a rad cap over 20 lbs?

25 lb cap on the cool side (low pressure side) of an HO style radiator (that is what you have on your renix right?), sounds like a sure way to blow up the radiator some day?

Other than that, sounds like you made some progress.

 

[nickguy]

Just wanted to check in after some time in summer driving. Just a note, I wanted to essentially "seal" the radiator (CFS) did not send me a RENIX radiator and the HD cap does that well. So to recap my current cooling setup.

CFS three row Radiator with 25lb cap
MAC alumininum RENIX style expansion tank with 14Lb cap
Spring in lower radiator hose
Hesco thermostat housing with brass fitting to allow for supplemental temp guage sensor and Painless wiring 195* on 185* off fan switch
(Have a manual switch and originally had a Corvette switch that came on at 210* my rig never gets at hot at the thermostat housing This could be the brass fitting I use to house the sensors as they are not in the flow so to speak anyway by the time it gets to 195* at the fitting it is time for the fan to come on) It is nice to have the auto fan switch there just in case you space the manual fan switch.
Hesco High flow water pump.
RobertShaw 195* stat
50/50 coolant and water wetter
Everything else stock (fan, hoses)


This is working like a champ!!... The surge in temperature I was getting uphill at high speed on the freeway is gone. I am convinced was my lower hose collapsing due to the high flow water pump. Th is is peculiar to me I think in that most of my trips start
with a blast up the freeway to the mountains. Temp at the stock sensor at rear of block stays solid at 195* and will edge up to 210* in heat under load fan comes on and cools appropriatly.

I think in retrospect that the Hesco purchase was overkill. My advice to anyone purchasing one with a RENIX rig is to make sure you have a high quality lower hose. I think that they need a spring but your mileage may vary