zipp-75

Okay, here is my question for all you guys out there with Dual fans and alm rads. Did you need to cut down your fan shroud in order to fill the space between that back of the radiator and the cross member?

I have sealed off everything there is to seal on the nose of the car – at least to the best of my knowledge. No magic here – she is a 75 convertible 4 speed – stock engine with some tuning done.

She does not over heat at idle – the fans cool her right down, but on the freeway she heats up more? Tacks high with stock gears – 3k. Other idea was water pump is going out, but I wanted to check in before I ordered an aml high flow.

Thanks for your time and suggestions

MotorHead

Did you seal off the air coming in from the front of the car ?

zwede

A Camaro I used to have started running hot on the highway but not in traffic. Turned out the timing was way off. Both retarded and advanced timing will make the engine run hot.

SteveG75

Did not cut my shroud down. Look at my photos. If you are not getting cooling on the highway, you are not getting air to go through the radiator.

Is the bottom of your radiator support sealed to the bodywork?
Are the sides and top of your support sealed?

Most important. Do you have the stock spoiler under the nose installed? This is critical to getting air to the radiator since our cars are "bottom breathers".

WayneLBurnham

Still running hot - EXACTLY like yours, except no runaway....up to 220-225 in hard cruise, but stable there. Too hot to cross desert or hold 140+/5K+, but nominal for now.

I ditched my shroud entirely. Tonight I will plug all the minor gaps, like I had with the shroud. I will measure to fill the space under the radiator to the crossmember with a plastic or aluminum sheet.

Mine is worse than yours. I have the 82 style nose, which is really incompatible with the 75 inner grill design from the standpoint of airflow. Since that isn't enough disadvantage, I installed an SSBC vacuum pump in the nose cone but it turned out I don't need it for this not-that-radical cam. Adding insult to injury required me turning my unused condensor into a remarkably effective tranny cooler, just to ensure my radiator ONLY sees 150+ degree air, and for more stupidity, I shoved a small oil cooler lower down in front of THAT just in case a little too much air was lining up to rush through to cool my engine sweat. (The oil cooler fitting JUST sprung the season's oil leak #17 and I simply bypassed it - only noticing about a 10 degree increase in oil temp, so THAT thing is just serving purpose on TOP of purpose!)

I also want to rig an expendable extension on my air dam to bring it about 2.5" off the ground to scoop more air. With the last radiator setup I added two bolts to the middle center to hold it down to grab air (it always pointed up for some reason, and no number of adjustments of the two big bolts and two added on leading edge connecting bolts could fix this.) The last time I was under there I also noticed a lot of air can go SIDEWAYS around the radiator arear behind the headlights to the side (wheel areas) and I'd like to do something to block that too.

Man though, ain't it great to be able to slow down, pull over and COOL DOWN now? Good luck!

BSeery

Another item to look at is the lower radiator hose. Have someone rev the engine to around 3K and watch the lower radiator hose to make sure it is not collapsing.

zipp-75

Timming is perfect - Good suggestions!

Discovered the lower rad to support seal is missing. Will install another one I have tomorrow.

All other seals are new and right.

Front spoiler is Pace Car style - should be good there.

Running about 195 on Freeway with fans running all the way. Driving me nuts really. Not sure how hot she will get if I keep going, weather was over 90 today.

I like that lower hose suggestion - I will look into that idea as well.

Nice to know I do not need to butcher my stock shroud.

Thanks for all your input, you guys rock!

CrossedFlags77

I wouldn't be too concerned if it was running 195* on the highway. I would be quite pleased with that.

Chuck Harmon

Two things to check:

1) Verify your temp gage is accurate, mine read about 20 degrees high.

2) Duntov had the same problem with the 68 Vette. Fine at idle, overheated at highway speeds. The problem was that air was trapped by a fan. Believe it or not, propeller driven air planes use their props as brakes when throttled back, coming in on approach. Duntov had a spring loaded trap door in the shroud that would open when air stacked up infront of the fans.

Above 30-35mph, you don't need any fans or shrouds, period.

Chuck

Chuck Harmon

Two things to check:

1) Verify your temp gage is accurate, mine read about 20 degrees high.

2) Duntov had the same problem with the 68 Vette. Fine at idle, overheated at highway speeds. The problem was that air was trapped by a fan. Believe it or not, propeller driven air planes use their props as brakes when throttled back, coming in on approach. Duntov had a spring loaded trap door in the shroud that would open when air stacked up infront of the fan.

Above 30-35mph, you don't need any fans or shrouds, period.

Chuck

Kalway

This thread is sort of a breath of fresh air to me. (no pun intended )

My engine overheated and cracked both heads in April (300+ degrees does that). Had the engine remanufactured/rebuilt to a 355. Lately I been running about 190 (somewhere under 200) or so on the freeway with the new distributor and carburetor. Glad to know I'm not really getting too hot in there.

PhotoVette1

Here is a post from a Volvo forum:

My 1989 240 DL warms up normally (temp. gauge on the mark), but after about 10 minutes of highway driving the gauge rises almost to or slightly into the hot zone. I can bring it back down to normal by turning the heater on full-blast.Coolant level is OK and not leaking, belts are tight, top radiator hose is getting hot so thermostat must be opening, the radiator hoses are soft but don't appear to be collapsing. I think it's actually overheating and not just a problem with the gauge, because the air conditioner output warms up when the gauge goes up. I guess I could just start replacing parts until it's fixed but would rather begin at the most likely source of the trouble. Where should I start?

Sounds just like what our C3's do.

I think the problem getting much worse with the a/c on is proof positive not enough air is passing through the radiator.

And just about every time, the fix is either a blocked radiator or the fan clutch.

I'm putting a new fan clutch on today; everything else is fairly new.

Razorhorn

I have the same symptoms as you, and I also have a 75. Get yourself an IR gun on Ebay for $50 and measure the temperature at the thermostat housing. Temp senders are NOTORIOUS for giving a false reading at the temperature gauge. My readout at the gauge is 22.5 higher than the actual water temperature and it's because of the temp sender. A friend of mine runs 15 degrees hotter than his gauge reads (a bigger problem than mine, but at least he knows about it).

zipp-75

Good point on the temp gauge. But, here is what I am seeing.

You would think with an L-48 motor, that has a Griffon rad with twin SPAL fans and a fan step controller I would not be having this issue. I am really using my AMP gauge to see how much the fans are pulling based on the sending unit they are using.

In order to test the system I also installed a 160 thromstat and they are still on at freeway speeds.

All I want is my fans not to be running all the time - no reason for it really. I agree the fans may be causing an issue if on at freeway speeds, but they have built in air diverters when at speed.

Today I will install the lower rad seal and put some water wetter in her to see how that does. If this does not do it, I am thinking I may be getting cavitation at the water pump at freeway speeds. Just maybe?

zipp-75

Pic of current setup:


Another angle:


Note: These were install pics - seals were not in yet..

71roadster

I have been running the same setup essentially and I have zero problems. In fact, my fans do not even come on when I am on the freeway, even on a hot day. I accidentally left the fans disconnected one day and went for a drive and noticed that it was heating up at stop lights but cooling down on the road. Made it home no problem.

I know you want an answer, but all I can offer is hope.

Good Luck,
Chris

zipp-75

I'll take hope right now! Thank you!

LiveandLetDrive

Ditto that 195* is not a problem, as long as it's stable.

Z-man

That's not even boiling plain water, and I assume you are running some antifreeze or additive plus a pressure system of about 14lbs. That would translate to a boiling point of 260 or so. As long as the block has liquid in it, you should be getting heat transfer, so 195 is fine.

I'd check timing also (like Zwede suggested) and possibly oil level. The oil acts like a container for heat...

427V8

same here.
My 450hp 434 small block was running hot in slow traffic, fine ideling, fine at hiway speeds. It normally runs abour 200-210 so this was pretty weird.

Turns out I had the fans running backwards, so they were trying to push air against the wind