V8 cooling issue

[sean_V8_914]

V8 runs hot when flogging it. i think the water pump may be cavitating ata higher rpm. in traffic it runs 185 for hours. at 70, 200, over 85 it will over heat 250+ if driven like that for 20 minutes. at the AX it gets to 230 is 3 laps. radiaator is huge, airflow is ample. no trapped aiar. has anyone seen this before?

[Kenny Powell]

Sean
I would say look at the thermostat,water pump and check out all your hoses and so forth especially if it has just started happening!
If all those items check out good the head gasket would be my next concern.

[John2kx]

Sean,

Pictures of your installation would help in troubleshooting. Without seeing it, I'll offer these:

1. Change thermostat out and replace with the Mr. Gasket "high flow" unit. It looks different than anything else out there and does flow more water when open due to its design. Available at Summit and Jeggs. This was the cause of my problem when first running my car in the Georgia heat. I tried several run of the mill t/s's until finally trying this one.

2. Check your hoses for possible kinks. The most common area is at inlet to water pump (this is about the tightest turn in the system). If you see a partially crimped section, try to eliminate by inserting a steel spring in this area to eliminate collapse at high rpm. The next most common area for kinks would be the two hoses exiting pump and running to block. Hard to see when installed in car but you can check by using mirror or feeling entire line when cool.

3. I've heard that a 50/50 mix of antifreeze/water does not cool as well as when running with less antifreeze. Pretty cheap and easy to try. You could drain two gallons of what your running and add fresh distilled water, purge system of air several times and see what happens. This would be a good time to use a flush kit as mentioned above.

4. You may have a damaged water pump impeller (pitched a blade) if you run a thermostat without addition of bleed holes. The bleed holes releave pressure at pump (protect impeller) while thermostat is closed. Renegade warns against operating engine over 2000 rpm until it begins to warm up.........this is without the bleed hole mod.. Checking for a thrown blade would be the last thing to try due to the level of effort required to disassemble pump.

5. You mentioned no air in system. What are you running for a recovery tank? Does the level in tank return to the same spot after a full cool down (overnight)? If not, your loosing water somewhere. If your sure there are no external leaks, it's time to test with pressure. Rent a cooling system leak tester and attempt to run down source of engine leak. Double check for external leaks with leak tester prior to checking anything else. As mentioned earlier, the hoses at front of engine cannot be seen very well. Check this area good while at pressure.

A blown head gasket or leak between intake to heads are the most common. A chocolate milk colored film on dip stick would indicate a on going leak of system. I have seen internal leaks that did not show this milky substance on dipstick.........probably due to the leak being new. If you can't hold pressure on test device (20 lbs. for 10 minutes is what I remember as a good test), you could drain oil from pan and pull all spark plugs. Leave drain pan plug out and again pressure test system. Water seen coming from oil pan plug or any of the cylinders would help pin point problem area.

6. A different rated pressure cap is easy to try. Renegade recommends a 16lb. cap for their system. If your using another cooling system, you'll just have to experiment.

7. Backing off timing is worth a try as mentioned by someone else.

8. Have you ever had air/fuel ratio checked? A lean mixture may cause engine to run hot. I had mine tested while on dyno to verify ratio was right throughout rpm range.

Is this something that just came about and have you operated car at your current ambient temperature before? If it all of a sudden occured, I'd go after thermostat and a pressure test.

Where is water temperature sender located? (heads, block, intake, other)

How dependable is your temperature measuring device (gage)? A second gage and sender is recommended.

Are you sure your water pump belt is not slipping?

Provide the diameter of your water pump pulley. There seems to be a couple different sizes being sold for conversion kits. The smaller one would provide more flow.

Are your water hoses routed in longs. or down center of chassis?

What size is your inlet to radiator? My hole is measured at 4" x 20" (80 sq. in.). It is recommended to have twice the outlet size as compared to inlet. Is the radiator sealed with a shroud? ie, inlet and outlet provide forced air through radiator and not allow air to escape through openings at any side, top or bottom.

A indicator of fan status is recommended (on/off light). The fans don't do much good over 40mph but you want to make sure they are cutting on when speeds are lower than this. You want to make sure fans turn on at about 175-180F as measured at radiator. You could have a situation where fans turn on too late and the system can never catch up.

Which water pump are you using? The Simpson is rumored to have a smaller inlet to pump as compared to what Renegade sells.

That's about all I can offer this early Sunday morning. Just as a comparision, my car runs @ 170-180 in traffic and about the same at sustained highway speed at 80 mph. With the recent addition of a/c, my in town temps. will go to 200F with near 90F weather, with highway temps. remaining at 170-180F.

John

[skline]

Wow, this is some good information. I am doing my conversion now and this will be great for when I get it done. Hopefully I wont have these problems. I opted for the Rod Simpson radiator kit complete. It was about $150 less than the renegade setup. The rest of my conversion parts are from Renegade however. I have seen Seans radiator. I think he should change it out for the aluminum ones used by Rod Simpson and Renegade. They are very efficient and small. I must say though, installing it was a little more difficult than I had thought it would be. I spent most of the day yesterday cutting the holes for the flow. Because it is a Chalon I have so much space between the spoiler front end and the body where the hole is cut, I am making sheetmetal to enclose the openings to channel the air directly into the radiator and it will be completely sealed. Hopefully that will help channel the air directly to the radiator. This is a great thread and I will be using any and all information I can get on this subject in hopes of eliminating any problems. Thanks all.

[sean_V8_914]

great info indeed. I think the high flow thermostaat will do it. I floggeed it hard all day ata teh track today . we had just enough time in teh grid before each run for it to drop into the saafe zone. I'll post pics asa soon as I fix my house computer where teh pics are stored

[John2kx]

Guy,

The bleed holes in thermostat follow the same principle as a bypass designed in the stock GM, Ford etc. water pump. I'm not sure if the original concept was to prevent cavitation or other pump related problems. In our converted cars, the bleed holes will also prevent blowing a hose off while in the same mode (t/s closed, pump spinning above 2000 rpm).

John

[John2kx]

Originally posted by 914GT
I knew you'd come through with a good explanation. And now that you mention it, the heater core made a bypass for the pump - at least on the older cars. One heater hose tapped off the top of the intake manifold next to the thermostat and the return hose into the pump. On my conversion I planned to use that same port on the manifold up to the heater core with a return line to the suction side of the pump through a Tee. But I don't have those hoses hooked up yet so I'm drilling the thermo holes like you recommend.

Guy,

The method you describe above will work in providing heat for cabin but won't perform the same function as drilling holes in t/s. Tapping into suction side of pump with one hose and the other connected at intake will still hold pressure until t/s opens with our style water pump. You would be providing water to heater core but until t/s opens, the water going back into intake is dead headed. The ideal method of providing water to heater core would be to use tap in intake as supply to core and tie in return from heater core in any location of supply line to water pump (from radiator exit point up to inlet to pump). Intake port is pressurized where the pump suction side is not......well, very little until system is at operating pressure. You'll also need a valve of some type intalled in supply line (to heater core) to prevent having heat on all the time.

John

[sean_V8_914]

Kragen, auto zone and Flaps all sell Milodan hi flow thermostat #16400. I paid 11.95 at Kragen

[AJS]

All,

I'm getting close to starting on my V8 conversion, and had a question about the opening for the radiator at the front of the body/bumper area. Can anyone post a picture of this cut out and/or provide a size and location? It would be very helpful. Also, is any bracing or strengthening required adjacent to this cut out?

Thanks,

Andy

[John2kx]

Andy,

I don't have measurements, but the attached pic should provide what you need. No added bracing is required.

John

[John2kx]

Bumper opening is 4" x 20". You should have twice this size for air to exit front trunk.

[John2kx]

a little more detail

[John2kx]

Exit opening

[John2kx]

asdfs

[Dave at Pelican Parts]

Cleeeeeeaaaaaannnnn....

I actually would consider an "X" brace across the opening, made of narrow tubing. Seeing a hole that size would make me a bit nervous.

Ditto the wheel well openings... Maybe a single diagonal tube? Hmm.

I'd have to do a whole lot of thinking about it first, as I'm not that familiar with what actually carries the loads in the front trunk other than the floor pan. Right now, I'm just reacting to the look.

--DD

[AJS]

John2kx,

Thanks for the pic's!! Is the cutout opening area greater than the 4"x20" opening in the bumper? It kind of appears that way. I should know this from your previous posts, but this looks like an RH radiator set up; correct? One more request: What are the dimensions of the RH radiator cooling area (area not including the tanks)?

Yes, I agree. A nice clean set up!!

Andy

[John2kx]

Guy,

I'd like to see pics of your install.

My design is actually the way Renegade is currently doing their installs. I went to Vegas and viewed their facility prior to performing the operation. I'll be honest, the wheel well openings were a concern to me as well but after seeing a couple of the RH converted cars that were driven on a regular basis, my mind was at ease. Scott runs about 100 more horsepower than I and also uses his car on the track.

Thanks for the compliments but I'm sure it would not have turned out this way without doing the Renegade factory tour. I took about 100 pictures and viewed them many times while putting my car together. I copied Scott's car in just about every aspect vs. trying to reengineer. I figured the guy who owns the company would be a good person to follow. The 6 hour tour consisted of viewing all the conversion parts, completed cars, builds in progress, cars with and without a/c and a couple of different ways of doing this. A 914 was raised on a lift to view areas I had questions about. I must say the education and photos allowed me to put my car together with confidence.

John

[John2kx]

Originally posted by AJS
John2kx,

Thanks for the pic's!! Is the cutout opening area greater than the 4"x20" opening in the bumper? It kind of appears that way. I should know this from your previous posts, but this looks like an RH radiator set up; correct? One more request: What are the dimensions of the RH radiator cooling area (area not including the tanks)?

Yes, I agree. A nice clean set up!!

Andy

Andy,

Yes, the entire conversion was provided by RH. The area you asked about is much larger than the 4"x20" opening in bumper. I'll get you some dimensions in the next 24 hours or so as my front trunk is full of interior parts right now (another project in the works) but I'll try to describe the openings for you. The radiator is the largest piece in the puzzle. The shroud is the same size as radiator as it attaches at front of radiator. The shroud reduces in size as it is mated to opening in front of car.......and then the smallest opening is in bumper.

John

[sean_V8_914]

[sean_V8_914]

air exits under teh car and haas an 18
'inch fan
I installed teh high flow thermostat, moved the teemp sensor from the thermostat housing to the intake manifold, added a straighter hose from thermostat to the expansion tank. these things made a small improvement but I dont have enough room on teh street to push it hard enough to reaally know since symptoms only show after long term flogging on the track or on a long road trip to AZ. pipes to teh rad are 1.25 inch