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240 Engine Compartment Heat

dandeluca

Member
Joined
Jun 17, 2020
Location
Bordentown NJ
So now my little project 91' 240 is up and running and I'm taking it on little trips here and there. The car seems to be running well. However, after a very short cruise around town I noticed the engine compartment and hood where awfully hot. Now my temp gauge reads normal. (I removed the 'temp faker' unit when restoring the dash.) I also know the cars is not boiling over or anything. This isn't really about 'overheating' per say, but how hot should it get under there? If I took a reading of the valve cover after a drive with a contactless thermometer, what should the ballpark temp be? Is there a rough way to confirm that the the temp sender and gauge are working correctly?

Thanks!
 
I don't know if that is a published technical specification but since the head will read about 200 degrees normally with the exhaust manifold well above that the surrounding area with air circulation might be somewhere around that.

Test the thermostat housing.

How much below . . . who knows.
 
Do you still have the under-hood insulation in place? See example below.
But yeah, most everything will get heat-soaked in there in the ~200 Degree Fahrenheit range. It's what the radiator, and thus air flowing through it are near.

See example:
eaTSssrw5h3RUG7oz_AtdqrYUrKQEycwqvsGPl-v13KMrG9DdxN8XNV4FPnAz_xijINn2u7ZVTzbFFViXVVaPCsf6cdBu5FX9C3jdHkR6QqGSK912ol5M1k
 
So in your opinion would it be worth it to install some heat shielding/insulation. (Seems hottest bear valve cover/exhaust manifold.

Not really necessary. Personally, if I had access to a junkyard and one came up that was in good shape for cheap, I'd probably get one to make under the hood look a little better.
But I'm not sure it would do anything.
 
Insulating the hood would only keep more heat in. You could test the thermostat in a pan of water. Also, there are resistance verses temperature graphs of the gauge sensor in the Volvo Green Manuals.
I think the ratio of coolant to water can affect cooling.
 
I took it for about a 30 minute ride shut the car down and hit everything with an infrared thermometer. Everything looked about right. I might pull the thermostat and test it soon but I think just a little extra heat was trapped there the other day because I was just puttering around town and never got it up to speed.
 
The hood blanket is there for noise reduction and to reduce heat damage to the hood paint job. As noted, it definitely does not reduce the under hood temperatures.

My 1987 745 B230FT had both an electric pusher fan and a viscous clutch fan. I experimented with running without the viscous clutch fan in non summer / non AC conditions. The engine would run just fine in terms of the coolant temperature without the viscous clutch fan; but, the under hood temperatures would get quite high. The engine normally did not 'smell' when running; but, with the viscous clutch fan removed the under hood temperatures were getting high enough under idle / low speed conditions to cause all the small oil weep spots to start gassing resulting in a distinct petroleum odor from the engine compartment. Re installing the viscous clutch fan reduced the high temperatures (and the odor) by increasing the airflow under the hood at low operating speeds. If you have a viscous clutch fan, make sure that the coupling is engaging at high temperatures and moving air. The couplings do fail.
 
I took it for about a 30 minute ride shut the car down and hit everything with an infrared thermometer. Everything looked about right. I might pull the thermostat and test it soon but I think just a little extra heat was trapped there the other day because I was just puttering around town and never got it up to speed.

You might check the air flow through the fan at idle. Use a short strip of newspaper and carefully move it around just behind the blades. I found a lot of air was recirculating around the fan tips, even with the shroud in place, instead of being pulled through the radiator. I have the five bladed fan with thermostatic hub and air conditioning.
 
I have hood blanket, and my engine is B200k. Hood blanket greatly reduce the sound level. Yes the engine-compartment is usually very hot place. But it is always been just like that, so i think it is normal. Exhaust manifold gets very very hot, even i didnt have turbo. I have viscous fan, and i can feel even rear of the car, how the fan push warm air out from the "engine room" under the car. I really like the engine, which comes to normal operating temperature almost right after the start.
 
Regarding hood insulation, you can install fatmat to protect your hood paint. Works pretty well. Not much difference in noise, but it keeps a lot of heat off the hood.

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It is always good to put new thermostat if it is feeling that temperatures are not ok with the engine. I use about 197F thermostat and seems that at least my engine like that. Temperature gauge is right in the middle position.
 
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