1949 Commodore 8 Overhaeting

Unknown

I have a 1949 commodore straight 8. I recently changed the engine and I am having an oveheating problem. I have checked everything.The water jacket is fine, I had the radiator flushed flushed the block & had the head cleaned.Im running a 180 thermostat it will run cool for a while then it just heat up.ignition timing is also right on I am lost with this one any help is greatly appreciated!

Jon B

Are you sure the thing is really overheating? Have you tried testing the heat sender? (Drain block partially, remove sending unit, put into heated pot of water whose temp you've measured, check dash gauge).



You've had the radiator flushed but have you had it flow tested? If there were various blockages I'm not sure this would be apparent from merely flushing.

Unknown

yes it will boil out the overflow and I have an aftermarket temp gauge.

I did have the radiator flushed and flow checked and it is ok. It never ran hot before I changed the engine it just has me baffled!

rambos_ride

KEVIN U wrote:

yes it will boil out the overflow and I have an aftermarket temp gauge.
I did have the radiator flushed and flow checked and it is ok. It never ran hot before I changed the engine it just has me baffled!

Could just be an air pocket getting trapped in the system and when it heats up it moves around til it blocks the water from passing.

I know you said you have an aftermarket gauge - I'd go even father and stick a manual thermometer into the radiator coolant - Hudson's probably didn't run much radiator cap pressure, still be careful! sometime the sending units just get haywire (While you're doing this can you visually validate that the water is flowing thru the radiator)

Thermostats sometimes stick, I'd maybe try another one, or running without one for a short time to see the behavior.

And just to check = You're not getting any water in your oil - ie oil is clean and not frothy looking?

Unknown

Thanks rambo,I did put a thermometer in the radiator it was definately hot. One thing you did say with radiator cap off the water doesnt seem seem to be circulating you should see it circulating I thought but it isnt maybe there is an air pocket or possibly pump not working properly.

Unknown

Have you run a leak down test and a compression leak test? Engine overheats are are caused by leaks going either way.

Good luck finding and fixing your over heating problem.

Uncle Josh

Geoff Clark mentioned a flaw in the water jacket in his Eight Cylinder article in the last WTN. I caught it just in time as I'm rebuilding a 40 eight.



The 3rd hole in the baffle is directly in front of the web in the block, thus blocking most of the water from that hole. He advocates opening the hole up a quarter of an inch both ways.

SamJ

It is always possible that your brakes are dragging...emergency cable problem or out of adjustment. After driving a bit, touch the rear hubs to see if they are hot. :cool:

Ol racer

Is it overheating at speed or in traffic? At speed is more a radiator and/or circulation problem, while traffic hot may be an airflow/fan problem . Put the Thermostat in a pan of water to test opening Temp. Ensure that all shrouds are in-place for air to go thru the radiator and not around. Check that the 'radiator fins'are not bent or clogged. If so blow out from behind with air or water hose.

[Deleted User]

How about the waterpump? You said you don't see the water circulating. I have heard of waterpump vanes being wore out. Rare but possible. Unless of course you put the pump off your old engine on the replacement motor.

Unknown

Could Be Collapsing Upper Or Lower Radiator Hoses. Orliglinals Had A Wlire Coil In Them To Keep Them Expanded, They Rust Away And Hoses Get Soft When Warm And Collapse And Stop The Flow. Have Seen This Happen Many Times. Let Me Know If New Hoses Help Bill Albright

[Deleted User]

I have seen hoses that collapsed on the inside and restricted flow cause overheating problems, did you put on new hoses when you changed the engine?



Harry

Clutchguy

A couple of things to "recheck" First,go to the auto supply or online and purchase an infared thermometer. Take this tool with you and go drive the car. Once you believe that the engine is starting to heat up or whatever symtom you are getting,pull over to a safe place,open the hood,and using your new tool,check the radiator top to bottom and side to side for heat distribution. You will probably find the radiator,even though it is moving coolant,is NOT up to total capacity. Eight cylinders require every inch of core space for cooling,and when they don't have it,they WILL overheat. Check for the differential in temperature,especially comparing the temp.on the outsides of the radiator to the temp in the middle. Lack of flow on the outsides=reduced cooling capacity=overheating. Use your new tool to diagnose the rest of the cooling system. The back of the block temp compared to the front area of the block. You can check tire temps with this also. I have found this tool priceless with endless uses. A 7# radiator cap is also very helpful. I guess that I personally haven't seen to many bad water pumps that are not leaking or have some other sign of failure,not to say it can't be??. Also,a longtime Hudson club member,John Macintosh told me that never to overlook other possibilities. His '41 eight cylinder had numerous years of cooling system trouble and he finally figured out by accident that the Heatriser was stuck CLOSED or just didn't open up when he would drive the car,and it subsequently would overheat after he drove it for 30-40 minutes. The senario here is that the rear cylinders do not get enough exhaust relief and it finally gets to a temperature that overcomes the radiator and will overheat/not cool down because of the excessive build-up of combusion chamber heat. The heatriser being closed on splasher engines will also cause excessive engine blow-by. I have proven what John told me countless times in the last 10 years and it has fixed numerous problems. The heatriser is always some kind of a problem. Hope this helps,and good luck

Park_W

Good tip by Clutchguy on the heat riser and the infrared thermometer. I'd be tempted to remove the thermostat temporarily and see if the problem disappears. It could be sticking. I don't subscribe to running these critters without a thermostat, but temporarily removing it would reveal if it's the cause.

Unknown

Thanks Clutch Guy The Heat Riser You Are Referring To Is It The One Right On Top Of The Exhaust Manifild Next To The Carburetor Because That Did Cross My Mind But I Wasnt Sure Of Its Operation.

Clutchguy

KEVIN U wrote:

Thanks Clutch Guy The Heat Riser You Are Referring To Is It The One Right On Top Of The Exhaust Manifild Next To The Carburetor Because That Did Cross My Mind But I Wasnt Sure Of Its Operation.

Yes,and I believe if the cotter key or what was there once[located on the very top] is parallel with the manifold,it is in the open position. I have found just because it is free it does not mean that it doesn't go closed when you are driving down the road. Remember,these springs are heat activated and are usually worn out!! I have found illiminating the heatriser has never caused any concerns with splasher engines,especially on the eight cylinder,since the carb is mounted on the exhaust manifold.

Unknown

Thanks Again I Will Try Removing It That Sounds Just Like My Problem Because It Doesnt Heat Up Right Away It Will Go About A Half An Hour And Then Heat Up!

Clutchguy

KEVIN U wrote:

Thanks Again I Will Try Removing It That Sounds Just Like My Problem Because It Doesnt Heat Up Right Away It Will Go About A Half An Hour And Then Heat Up!

Kevin,just remember-LACK of capacity can still be the base of your problem. An infared thermometer is a great tool to diagnose this with. You can also use this on the exhaust manifold and check for heat distribution,front to back. I also use the infared to determine the truth of my factory temp gauge. You can use this method on all cars. Using the infared,with the engine at its normal running temp.,put the red dot on the temp sending unit and read what the temp is in comparison to what the gauge is actual registering. This gives you a reference when you are out and about in your car. If it is running cool or running a little hot. I have found most Hudson gauges read on the high side of the temp gauge and are only running around 160-170 degrees.

Unknown

My Dad Had It Checked At A Radiator Shop With An Infrared Light And Was Ok Maybe Its Different Under Driving Conditions.

Unknown

Thanks alot for the info I disconnected the the heat riser a wired it open and the engine ran a consistant 150-160 degree even at highway speed that where it usually would get hot. The only time it even got warm is when we climbed a steep hill it went to 190 which isnt really hot but it never overheated. Thans again for the info it helped out alot.

Huddy42

On all the Hudsons I have owned ,I have removed the heat riser altogether and never had any hint of overheating, replaced it with a nut and bolt, if anything the car runs too cool, usually around the 150 deg mark and we don't run thermostats, can not remember the last time I saw a splasher motor running with a thermostat down under.

rambos_ride

Huddy42 wrote:

On all the Hudsons I have owned ,I have removed the heat riser altogether and never had any hint of overheating, replaced it with a nut and bolt, if anything the car runs too cool, usually around the 150 deg mark and we don't run thermostats, can not remember the last time I saw a splasher motor running with a thermostat down under.

Removing the heat riser wouldn't make it overheat - just take a little longer to warm up.

The heat riser is meant to restrict the exhaust just a little on startup then transfers heat to the choke(s) on some cars - others it just restricts the flow a little.

The only problem with running without a thermostat - it takes longer to heat up, and you might not actually be running at optimal engine temperature at 150 degrees if it's meant to run hotter.

Park_W

I'd say the heat riser temporarily (we hope) re-routes some or all the exhaust from half the engine so it warms the intake passages below the carburetor on the way out to the exhaust pipe. On the older cars at least, the auto choke receives heat from the exhaust manifold regardless of what the heat riser's doing. I agree with Geoff that it's not much of a probolem to run without the heat riser or with it fixed full open. In "the old days" I ran a splasher 8 with the carb mount part of the exhaust manifold completely separated from the rest of the manifold. As said, it just took a little longer to lose the cold startup behavior.

[Deleted User]

It's my understanding that if you run below optimum operating temperature [without a thermostat] the rotating engine parts will wear at a faster rate. ,especially the rings. It may not hurt the older engines but I'm sure it must affect performance somewhat.

Clutchguy

[Qoute] The heat riser is meant to restrict the exhaust just a little on startup then transfers heat to the choke(s) on some cars - others it just restricts the flow a little.





On a Hudson splasher engine it restricts the flow more than 60 percent. Sometimes if you look at a splasher engines manifold,look to see if all the paint is cooked off or the manifold is a real different color on the rear 3/4 cylinders. The pressure that is created from the lack of flow has to go somewhere,so it makes excessive pressure in the rear cylinders and subsequent pushes exh.pressure passed the rings and causes all sorts of problems. If you have every taken the head off a splash engine and the top of the block and engine parts are all pitted real bad,I have found that the heatriser was the culprit. I have seen the valve seats burnt up real bad,only on the rear cylinders,the exhaust manifold bolts all heat broken off,the manifold cracked horribly and the gasket is blow out .You can also find the passage from the rear going around the intake ,warming it up will be carboned almost shut and creates more of a restriction. I should take some pictures of the junk exhaust manifolds in the junk iron pile and post them. It has been a busy summer for them.