Overheating Issues
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
Overheating Issues
Looking for input. I recently somewhat completed my 68 restoration. During the motor rebuild (L79) I decided to rebuild my original water pump. Fast forward, I've been having hi water temps during the sorting out phase. I've do have a new DeWitts radiator, 180* stat, new temp sending unit, new shroud seals. The fan clutch was orginal and I observed it free wheeling on engine shut down, so I just replaced it with a OE Eaton style. Took the car out for a test and all efforts failed. She flirted with the red zone. I removed the expansion tank cap, started back up to observe the water flow rate. I have to say I do not know what I was expecting but the water in the tank barely shows movement. Is this normal? I do also have a new heater core. Like I said I performed a full nut and bolt restoration. A bit frustrated. Please chime in.
Thank you,
Peter
Thank you,
Peter
Le Mans Master
Joined: Jun 2019
Posts: 5,328
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From: Loveland
I have an L79, 1968. When I reset my timing to Lar's spec my temp lowered. Also is your guage reading correctly? I have heard of bad-incorrect sending units. Is it boiling over or just reading high?
Burning Brakes
Joined: Feb 2014
Posts: 1,045
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From: Cape Neddick Maine
2020 C3 of the Year Finalist - Modified
are you sure the gauge is reading correctly? can you check the temp with an infrared temp gun? do you have a fluke meter with a temp sensor. have you thought of pulling the thermostat because I have had bad ones right out of the box that wont open. before you put a new one in check it in boiling water to make sure it works.
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
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From: Monson MA
I was taking the reading at the thermostat housing. I was get about a 40* difference between the top hose and the bottom.
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
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From: Monson MA
no idea before. I bought the car 10 years ago. Pushed it onto a trailer and brought it home. It sat for a year or so than I started with disassembly. Every nut and bolt has been touched. New radiator, hoses, stat, fan clutch. The only non new part is the water pump. I rebuilt it. But I played with the timing today and the car ran within temps 180-200 via a inferred thermometer. However my gauge was lying to me, telling me 230+*.
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Team Owner
Joined: Jan 2006
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From: Crossville TN
Or is there some problem with the gasket which is limiting water flow?
We know that the DeWitt's radiator is NOT your problem (right TOM?
). My estimation of the most likely problem causes (in descending order) are:
1. Bad thermostat (I always test a new stat in a pot of boiling water to make sure it fully opens at 212F); {lots of 'new part' junk being sold these days}
2. Temp gauge/sender;
3. Fan, shroud problem.
4. Problem with water pump / gasket installation:
With a DeWitt's rad and a 180*F stat, your normal operating temp should be 180* or somewhat less, unless it's a very hot day and/or with A/C on.
We know that the DeWitt's radiator is NOT your problem (right TOM?
). My estimation of the most likely problem causes (in descending order) are:1. Bad thermostat (I always test a new stat in a pot of boiling water to make sure it fully opens at 212F); {lots of 'new part' junk being sold these days}
2. Temp gauge/sender;
3. Fan, shroud problem.
4. Problem with water pump / gasket installation:
With a DeWitt's rad and a 180*F stat, your normal operating temp should be 180* or somewhat less, unless it's a very hot day and/or with A/C on.
Le Mans Master
Joined: Aug 2005
Posts: 6,493
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From: Temple Terrace Florida
Is it possible that the block, especially in the lower end, id clogged with rust. Who knows what was done or not done in its 52 year life. My 68 with an L-79 and AC with a Dewitts radiator sits at 180 all day long in the Florida summer. Jerry
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From: Im not allowed to tell you
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TO answer your question, i dont think you can puut the ompellor in backwards. You could buy a new highflow aluminum water pump and see if it makes a difference if all else fails. Thats my next change.
As for the gauge, you can buy Willcox's temp gauge adjuster and that will get your gauge reading correctly. Idling at 190 is normal, you have no real air flow. My L79+ would do that but once I got moving the temp would drop. Get the adjuster and get it so it reads the thermostat housing temp, then take it for a drive on the highway at 65mph and see where you are. Above 75 my car would start to heat up again due the the high rpms from the final gear ratio
With the thermostat open you should see the fluid flowing in your expansion tank. If you still have issues you can pull the thermostat completely and see what your idle temp stabilizes at and at what ambient air temp that is. Then do a highway temp. If your seeing a higher temp at rpm than you like your lower radiator hose could be collapsing. My car definitely responded differently depending on the outside air temp.
As for the gauge, you can buy Willcox's temp gauge adjuster and that will get your gauge reading correctly. Idling at 190 is normal, you have no real air flow. My L79+ would do that but once I got moving the temp would drop. Get the adjuster and get it so it reads the thermostat housing temp, then take it for a drive on the highway at 65mph and see where you are. Above 75 my car would start to heat up again due the the high rpms from the final gear ratio
With the thermostat open you should see the fluid flowing in your expansion tank. If you still have issues you can pull the thermostat completely and see what your idle temp stabilizes at and at what ambient air temp that is. Then do a highway temp. If your seeing a higher temp at rpm than you like your lower radiator hose could be collapsing. My car definitely responded differently depending on the outside air temp.
Last edited by Rescue Rogers; Jun 2, 2020 at 10:19 AM.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
Plenty good suggestions ... her's a Q re coolant flow thru block etc ...
? During resto, did you have a shop either boil out or bake&blast block, heads & intake ... maybe you pressure-washed (ok) in lieu of ?
OTOH, Yes, typically std rotation impeller can be reversed (& vv) but usually makes little performance difference. I did it using a reverse rotation C4 short alum pump on CT car w/ CT pulleys.
? During resto, did you have a shop either boil out or bake&blast block, heads & intake ... maybe you pressure-washed (ok) in lieu of ?
OTOH, Yes, typically std rotation impeller can be reversed (& vv) but usually makes little performance difference. I did it using a reverse rotation C4 short alum pump on CT car w/ CT pulleys.
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
Plenty good suggestions ... her's a Q re coolant flow thru block etc ...
? During resto, did you have a shop either boil out or bake&blast block, heads & intake ... maybe you pressure-washed (ok) in lieu of ?
OTOH, Yes, typically std rotation impeller can be reversed (& vv) but usually makes little performance difference. I did it using a reverse rotation C4 short alum pump on CT car w/ CT pulleys.
? During resto, did you have a shop either boil out or bake&blast block, heads & intake ... maybe you pressure-washed (ok) in lieu of ?
OTOH, Yes, typically std rotation impeller can be reversed (& vv) but usually makes little performance difference. I did it using a reverse rotation C4 short alum pump on CT car w/ CT pulleys.