L695speed

Hey guys I've got coolant boiling in my overflow bottle. I'm suspecting one of two things. Either the Thermostat, or the rad cap is not pressurizing. My temp gauge reads in the 100-200 range, and running for five-ten min at idle before it boils. I know I don't have an internal problem as there is no steam coming out the tail pipes, oil is clean, coolant is clean.

Other than those two minor things is there anything else that could cause this?

skirkland1980

iTrader: (2)

if your engine is overheating here is what to do. First make sure the coolant system is full and no more antifreeze than 50%(ethylene glycol) you will need an infrared thermometer (about$90) or borrow one. get the engine up to operating temp. if the car has a 190 degree thermostat the engine needs to be at least 190 degrees. if you have removed the thermostat replace it. get a good quality one. now that the engine is hot turn it off and take the infrared thermometer and scan the entire cooling system from the thermostat housing to the water pump inlet. the thermostat housing and upper radiator hose should be at least 190. if not here is no coolant circulating. check the water pump and thermostat. scan the radiator core at all 4 corners and center. look for a temp drop of 15 degrees or more. if the radiator doesn't have have a consistent temperature replace it. if everything else checks ok it is likely an airflow problem. make sure the radiator is getting fresh air and the fan(s) is working

91interceptorZ

iTrader: (3)

like 5 min cold?? like motor isn't even warmed up yet and it starts boiling over?? Then you have a head gasket or head problem, pumping compression into the cooling system, causing it to overpressurize and "boiling" into your overflow. You would not always get coolant into the exhaust, so it may not be evident. Let motor go cold, take off cap, and then start engine, if it starts bubbling and coolant really isn't that hot, then it's combustion in the cooling system. that's one way to check, the other is go to a shop and have them use a 'sniffer' to check for gases in cooling system.

If the coolant in the overflow is hot, you could have an overheating problem do to a sticking thermostadt.

L695speed

I doubt its a head issue because the motor was rebuilt at 80K miles (the one that was swapped in that is). I am waiting for the motor to go cold now and I'm going to check (if I have something to check it with) the temp on all four corners. I could feet the top hose was warm but didn't feel pressurized. Also it was running for at least five, the engine was warm as it was run before (I was setting the timing) so it may have been running for at least 15-20 minutes total before I saw the overflow boil. My overflow bottle is cracked to hell, and finally I forgot to mention here (I did in the other one in general engine) that the fan never came on the whole time. I would suspect that it should have come on by the time the motor was warm. So it might be either a pressure issue, or a fan issue. Sorry I left the fan part out as that might change your response.

L695speed

Ok guys I found a coolant system tester that I remembered I had laying around. Tested the cap, it failed miserably. So, I'm going to start there. Could be that because of no pressure due to the bad cap it overheats quick. I remembered I had the same problem of boiling coolant when I had the heater core fail. During that trip I was probably avg about 50 mph so due to the airflow going through the radiator it could be possible that is what helped it stay cool til the heater core failed and lost pressure. Maybe the cap was faulty then too and I didn't know it til now. I'll get a new cap and let y'all know how I make out.

Drew86maro

Yeah a new cap wont hurt anything. My Camaro's coolant bottle was boiling like that before, I replaced the cap to be safe but it ended up being the fan. It wasnt coming on until the engine was way to hot. So check and make sure your fan is doing its job and coming on at the right temp or make sure it even comes on at all... Good luck.

L695speed

I'm suspecting the fan now....... Replaced the rad cap and I had pressure, but was still boiling. Again, I'm thinking I had the same problem with the overheating like I did the night the heater core blew. Because the car was running it was staying cool. Sitting still it over does it. Any voltage specs for the fan to be sure power is getting to the fan? I'm not thinking head gasket yet. Also my temp gauge doesn't seem to be working........swings when it starts then settles at 125-150 range.....doesn't move after that. I think I have a 180 Thermostat and it works as the top hose is warm. So it is getting to operating temp but still no fan working yet.

The_Wraith

I Had this problem when my cooling fan didn't kick on. There was a also a slightly loose rad hose. Never in my case was it a headgasket issue. SBC's are near bulletproof there is a very slim chance the headgasket is the problem.

L695speed

I thought as much about the headgasket. Besides the motor was rebuilt at 80K miles and had about 86K on it when we got the donor car. So, that goes out the window. I ordered a fan assembly and a coolant overflow bottle from Third Gen ranch. I've had good experiences with them. So I should have those items sometime next week I'd suspect. Please let this be the end of the project mechanically.....

L695speed

I just had a discussion with a guy I know, he mentioned the change from the mechanical fan to the electric fan and you need a switch. I'm almost certain I did grab the switch and put it on and its hooked up. But I'm not positive. If that is the case then I'll have a spare fan in case mine malfunctions. Considering how cheap they are from the JY its not a bad move. I'll check for it when there is light in the garage, now, why do these things have to be almost impossible to get at? At the back of the right side of the motor....heater box, starter, etc all in the way, fml.

L695speed

I just found the wire and connector for the cooling fan switch. Its not hooked up and I doubt I even have the switch. On these 87 LG4s is it possible to get a switch in there so you can use the existing fan? I know some 84 L69s were retrofitted with belt driven fans, so it is not a bad idea to get a mechanical fan and shroud and use that til I rebuild the L69 and can use the electric one. I know just by looking at it its not going to be easy trying to get the switch in if I have to pull a plug out or whatever to put the switch in. There is no room near the heater box to even change the plugs without contorting your arm at some ridiculous angles.

L695speed

Ok, Sorry guys throw all that out the window, fan works, but it doesn't come on because the switch is not in the head. The guy I know brought up the rad and how they might have the coolant fan switch in the rad itself. Looking down the line it seems like there is a switch, but I don't know if it is one. The rad in the car now is a generic 82-92 replacement for these cars. Do the later ones have the coolant fan switch that gauges temp. in the rad on about half way down the passenger side? If that is the case then I might be able to either get some wire and a new connector and hook it up there or two I might be able to wire the plug and the sensor together.

Gregzz4

As far as I know, for your car, the sender in the rad is only a low coolant sensor
The temp in the rad will never be enough to turn on the factory switch you need that reads the Head temp
Example is this....
Head temp may be 180-190-210, whatever
Rad temp on the pass side is cooled coolant going back to the motor @ possibly 150-160, depending on how well it's dropping your temps
Switch will never engage the fan

L695speed

Ok, it was an idea but I wasn't sure if it would work because of what you just said. Looks like I may have to ground a hot wire to a manual switch and turn on the fan from inside the car when I start it up. That seems to be the best solution with what I've got if it is going to be next to impossible to get a fan switch into the LG4 head.

L695speed

Ok I found the plug in the head, felt like a 3/8 square. Tried to get at it with a 3/8 extension and it didn't fit. I struck out trying to find a next size down or two square key for a ratchet. I tried to pop the mainfold off for a clearer picture but I don't think its worth the work to do it. Has anyone found a square key maybe 5/16s? I believe its the right size but I'm gonna need all the leverage I can get so something small is out of the question. I have a coolant fan switch on order. Its just a matter of getting the damn plug out. NO I AM NOT DRILLING IT.

L695speed

Ok guys, I spent the better part of the weekend and this morning trying to get that cap out so I can put the switch in. In short, its not going to happen without serious work. As we all know there is no room whatsoever on these cars with the AC, exhaust manifold and so on all on the passenger side. I'm going to go the route of hooking up the fan to a switch via the battery. I'll flip the fan on when I start the car. Eventually I will get the fan switch in the head whether its this motor or when I rebuild the L69 I don't know. So, me and my brother are going to work on setting that up. I know the car was overheating because the fan was not on. So when I flip the fan on I should be in good shape. Just wish I knew I was going to have to do that before I put the motor in. It would have been a piece of cake three years ago when the motor was out of the car.

sonjaab

Best off wiring up a in-car fan switch ! Thats how mine is rigged up. But the only
downside is if anyone uses your car and doesn't know to turn the switch on
you could wind up with a cooked engine. A better solution IMO is to hook the
fan up to a key-on power source so the fan is on when the engine runs.

The ultimate solution is to scrounge up a mechanical fan and shroud set up
and throw the e-fan set up away! A positive no muss no fuss no worry solution !

My l-69 just came out of storage and I will have the mechanical fan set up
installed as soon as the weather breaks ! A $25 solution from the pick a part
yard!

L695speed

Thats not a bad idea either. I did look at the mechanical fan idea but.......I don't know. Thing is eventually like I said I might rebuild the original L69. Since I want it the way it came from the factory then the electric fan stays. The fan works and I've got another on the way as a back up.

L695speed

I've been digging around on manual fan switches. Correct me if I am wrong but...it seems like all you need to do is ground the wire that goes to the coolant fan switch (dark green one) and it will turn on when the car is turned on. Either that or it will be on all the time. Either way it seems like I can just use that same wire as a basis for a switch if I extend the wiring and run it into the car. Run the wire through a switch and ground it to the chassis somewhere and flip it on when I start it up. A quick response would be appreciated so when I go to the parts store I can turn the head mounted switch around and use the money towards a regular toggle switch and some wire.

deadbird

Correct.

L695speed

One last Q before I do this. I read somewhere that a ten amp switch will do the job just fine so that is what I got. Am I set to go or do I need a bigger switch?

Drew86maro

Glad to hear you figured out your problem, i was going through the same thing when my Camaro was overheating because that stupid fan was not coming on, the fan was the last thing I thought of. anyways you should be good to go now.

Gregzz4

I can't tell you for sure if a 10A Switch will do the job. Some aftermarket fans can draw as much as 25 and 30A.
I had an aftermarket fan that killed a $70 Hayden fan Controller, even though the kit comes with a relay and all.

I was going to suggest one last thing you research.
What I mentioned above may work for you. The kit comes with a threaded bulb that you put in your intake. You can dial it where you like it and it has a 20 Degree range. So, if it comes on @ 210, it turns off @ 190.
I'll post it here in a min when I find it

Gregzz4

Well for whatever reason I can't find the Hayden part #
Looks like it may have been discontinued, and I see why
There are other brands if you want to check it out

The idea is, you get a kit with a probe that threads into the manifold. I don't really like the ones you put in either the rad fins or inside a hose under a clamp.
The threaded ones are best.
The control box, as I previously stated, allows you to fine tune on/off temp of your fan.

L695speed

I hear what you are saying about shutting off the fan. Its a good idea to do something like that. However, since I'm not intending to keep this motor forever, and the car is on a historic registration its not a daily driver. I'll look into it. But for a car that is going to be driven during the spring -fall months on warm nice days I'm going to just let the fan run. If the car is having issues I'll look into it further. But it seemed to run just fine without the fan as long as the car kept moving. so really this is more of an issue when the car is sitting still than when it is moving. I know my brother said with the Fieros (he has one) he said people rig up fan switches all the time to keep the engines cool. Most of the time they just let them run.

Thanks for the tip, and I'll try the ten amp switch. If that doesn't work then I'll go bigger.

Gregzz4

Good luck
All you need then is to install a toggle switch with a fuse, or wire the power from the fan to the ignition, again with a fuse
Sorry I haven't read all the posts
Hope you have it figured out

L695speed

I was going to use the coolant fan switch wire, (only comes on when grounded with the key in ON position) connect a similar gauge wire to the wire after clipping off the connector that was on there originally, run one end to the ground on the passenger side fender near the battery from the switch, and the other from the coolant fan switch wire to the switch. Therefore it will only come on when I flip the switch to complete the circuit, and if I'm doing 70 on the highway in cool weather I can turn it off if I wish. Makes sense. I did think of just grounding the coolant fan switch to the fender ground as it only comes on when the key is in on. but warnings on the fan shroud say it can come on at any time so I don't know what that means. But because of that I'm going to run it through a switch.

Because I'm using the same system of relays and fuses that was there originally except I'm turning it on and off manually I think I'm good if I just do that. But if I do need a fuse in the line what size fuse would you recommend?

L695speed

Ok I wired the ground to the one by the battery, ran it past the A pillar and fender through the gap, to the switch. Then I hooked the wire that went to the original switch to a in line fuse with a twenty amp fuse. Ran a line from the other end of the in line fuse to the switch. The switch was a 20 amp switch. Tightened everything up, hooked the batt back up. Threw the switch with the car on, fan came on. So I have a working fan again. now I just gotta do something to insulate the back of the switch somewhat, and tape it to the dash near the light switches. I'm not drilling holes into the car because this is not a permanent solution. Eventually I'll re do the L69 and put that back in. But for now this is good enough. And the best part, I can take it right back out. Thanks for the assist fellas. Now to nail the timing down and put the aircleaner back on I should be good to go.

deadbird

It only takes roughly 250mV to power the coil in a relay (that makes the contacts close). The contact side of the relay is passing the high power to the fan.

A high amp switch is only needed for direct wiring the fan.

You're only adding a controlled ground tothe coil side of the relay (protected by underdash fuse).