temp gauge/ overflow issue

[Wilson_]

Here is the deal, I work swing shift and go to work around 230pm and leave work at midnight.

On the way to work truck runs fine temp gauge (auto meter sport comp) stays at 180.

on the way home the truck runs fine but about 5-10 mins into the 20 min drive home the gauge pegs at 250 very fast, then drops down to 200 then a little slower pegs again then drops to 180 for the rest of the way home. I do loose coolant about a 1/4 of a gallon or so that spills out.

The probe for the temp gauge is in-between the 6 and 8 cly in the head. Should I move it to the front of the intake mani?

Here is what I have tried.
New thermostat and housing. ( the old one was pointing straight up and was off of a tbi motor)

New 16psi Radiator cap. Truck has a 87 Trans am Radiator in it. should it be higher than that??

I tried burping the system with the front of the truck pointed uphill with the rad cap off and running.


Also the truck has no heater and all the holes have been plugged

Any ideas??

Thanks

[petey-pablo]

I had an issue simular to that it would run fine in normal stop n go traffic and in short distinces then temp would climb up on longer drives or up hill. But then go down to normal when I slow down for traffic or come to a complete stop. Had it check and my Radiator was plugged. Do you hit traffic on your way to work, Then on the way home just drive higway speed with no traffic maybe it could be that? It is weird though hope you get it fixed soon

[cdowns]

what type of fan setup are you running??


has this system been run without problems for a longer period of time?


if it's a junkyard radiator was it ever cleaned and tested prior to use?

[68gmsee]

Maybe going downhill to work and uphill back?

Seriously, drain all the fluid and refill with clean 50% water and 50% anti freeze or even 60% water 40% coolant. Then install an overflow tube.

You can make you a cheap one out of pvc hot water tubing (I used black from Lowes) Cap it at both ends and glue just the bottom one on. The top should fit snug but can be removed if you need to. Drill a hole just large enough to insert the radiator overflow hose in it almost to the bottom.

Place it in any convenient place and use nylon ties or large clamps to secure it. In my 68 it fits betwen grill and radiator support.

Solved my overheating problems and kept me from losing coolant. I've had it for about 2 years without any problems even in this Texas heat...

[Wilson_]

Originally Posted by petey-pablo

I had an issue simular to that it would run fine in normal stop n go traffic and in short distinces then temp would climb up on longer drives or up hill. But then go down to normal when I slow down for traffic or come to a complete stop. Had it check and my Radiator was plugged. Do you hit traffic on your way to work, Then on the way home just drive higway speed with no traffic maybe it could be that? It is weird though hope you get it fixed soon

Around here the traffic on the free way is about the same at those times well there are less cars at midnight. but I go the same speeds.

Originally Posted by cdowns

what type of fan setup are you running??


has this system been run without problems for a longer period of time?


if it's a junkyard radiator was it ever cleaned and tested prior to use?

Stock fan set up, The radiator came out of a running trans am that was wrecked (sideswiped) it was not cleaned or tested because of above.

Originally Posted by 68gmsee

Maybe going downhill to work and uphill back?

Seriously, drain all the fluid and refill with clean 50% water and 50% anti freeze or even 60% water 40% coolant. Then install an overflow tube.

You can make you a cheap one out of pvc hot water tubing (I used black from Lowes) Cap it at both ends and glue just the bottom one on. The top should fit snug but can be removed if you need to. Drill a hole just large enough to insert the radiator overflow hose in it almost to the bottom.

Place it in any convenient place and use nylon ties or large clamps to secure it. In my 68 it fits betwen grill and radiator support.

Solved my overheating problems and kept me from losing coolant. I've had it for about 2 years without any problems even in this Texas heat...

I do need a overflow tank asap. Does anyone have a pic of a stock set up in a 67? I have all the parts I just cant remember how it mounts.



I will try and get a video tonight

[cdowns]

they did not come with overflo tanks in 67


do you have a fan shroud to move air effectivly thru your radiator for cooling??

with that year radiator, if it has the stock 80's radiator cap you need to have a closed system.. radiator caps for the earlier cooling systems in 67 are made to function differently

[Wilson_]

Originally Posted by cdowns

they did not come with overflo tanks in 67


do you have a fan shroud to move air effectivly thru your radiator for cooling??

with that year radiator, if it has the stock 80's radiator cap you need to have a closed system.. radiator caps for the earlier cooling systems in 67 are made to function differently

no shroud, It was never an issue before.

The cap I bought was for the radiator I have. It is a 16lb cap. What is the difference with a closed system??

The upper hose I have, I think is trapping air. It is one of these universal radiator hose's


My question is why does it do it only at night and not in the day when it is 95+deg ?

Would I get a more accurate reading if I move the sender to the intake Manifold?

thanks for the help

[cdowns]

when you drive to work then turn off the engine the temp continues to rise due to a wrong cooling system that you've bubbad up and at night you go out and youre low on coolant so it gets hot

less accurate in the intake best place is drivers side head

i think you can solve either by completeing the closed cooling system correctly or installing a 1967 type rad cap

but either way may still b somewhat marginal without a shroud

[johnechi]

I'm using a HD 180 deg thermostat, Griffin aluminum radiator, HD fan clutch, HD upper and lower flexhoses, and an overflow tank.

The original water temp gauge was acting funky, showing temps going up and down. I had replaced the sending unit but I guess the ones currently available do not have the correct ohms resistance.

So I went with an autometer electric temp gauge, sender in the side of the head.

Temps are under control now, no hotter than 200-205 deg on the worst day and I no longer lose any coolant.

[Wilson_]

Originally Posted by cdowns

when you drive to work then turn off the engine the temp continues to rise due to a wrong cooling system that you've bubbad up and at night you go out and youre low on coolant so it gets hot

less accurate in the intake best place is drivers side head

i think you can solve either by completeing the closed cooling system correctly or installing a 1967 type rad cap

but either way may still b somewhat marginal without a shroud

What would I need to add to complete the closed system? If I wanted to go that way.

I will grab a new 67 style cap here in a few mins and see if that helps.

Thanks for the insight.
But it still does not explain why after the very quick spikes it drops down to normal operating temps for the rest of the drive.

I will also swap the sender to the drivers side and see if that helps.

Originally Posted by johnechi

I'm using a HD 180 deg thermostat, Griffin aluminum radiator, HD fan clutch, HD upper and lower flexhoses, and an overflow tank.

The original water temp gauge was acting funky, showing temps going up and down. I had replaced the sending unit but I guess the ones currently available do not have the correct ohms resistance.

So I went with an autometer electric temp gauge, sender in the side of the head.

Temps are under control now, no hotter than 200-205 deg on the worst day and I no longer lose any coolant.

I have never had the stock gauges in. The po had some no name brand gauges that never worked right. So I swapped them all out for autometers.

[Wilson_]

Originally Posted by 68gmsee

Maybe going downhill to work and uphill back?

Seriously, drain all the fluid and refill with clean 50% water and 50% anti freeze or even 60% water 40% coolant. Then install an overflow tube.

You can make you a cheap one out of pvc hot water tubing (I used black from Lowes) Cap it at both ends and glue just the bottom one on. The top should fit snug but can be removed if you need to. Drill a hole just large enough to insert the radiator overflow hose in it almost to the bottom.

Place it in any convenient place and use nylon ties or large clamps to secure it. In my 68 it fits betwen grill and radiator support.

Solved my overheating problems and kept me from losing coolant. I've had it for about 2 years without any problems even in this Texas heat...

Sweet. I will check this out at home depot in a few mins

Thanks

[Wilson_]

I got a new cap, It looks pretty much the same as the other one but we will see how it works.

I will let you guys know tonight.

[oldgold70c10]

You can make yourself a pretty nice "factory" looking setup with an extra washer bottle and bracket:

As long as you have the tube that attaches to the underside of the cap, it will suck water back in.

[tim21391]

could it have air pockets in the radiator? thats what happened in my eclipse

[pat 70/71]

as stated earlier I would put a shroud on it /clean out the rad/ get the proper cap/overflow bottle and be done with it. (the only time my truck got hot it didn't have a shroud) so I learned from this and will never run without it again best of luck. cheers, Pat

[68K30]

Make sure that neither of the hoses is sucking shut, soft hose or no internal spring. Recently had this happen on a 70 440 Cuda, only ran hot on the highway.

Bill