Overheating multifuel

[hsfdchief200]

I just changed out the #6 piston (that was burnt b/c a faulty injector had it running lean) and sleeve from another LDT-465. The head gaskets were changed as well. A new thermostat was installed. Now, the engine gets so hot that you cannot even touch the top of the radiator. There is a lot of pressure in the cooling system. It builds up pressure pretty quickly after the engine is started. I don't know what temp the engine is running at b/c the gauge doesn't work. BTW, there is no white smoke in the exhaust to indicate a blown head gasket. The power is still good, also.

What could be causing the overheating and pressure issues?

 

[73m819]

exhaust gases into the cooling ( maybe the head gasket didnt get set right) this is just a guess

 

[rdixiemiller]

Pull the alternator belt off. Fill the rad. all the way to the top of the filler neck (engine cold). Leave the rad. cap off. Start the engine and watch the water in the rad. If you see bubbles, or water starts pushing out in the first minute or so, you have a compression leak into the water jacket. Sounds like a head gasket was installed wrong, or just decided to leak. Did you check the heads for cracks? The multifuel manuals call for re-torquing the head after it warms up.
I'm not sure on the multifuel, but on some engines the head gasket can be installed upside down. That will open up some water passages and cause leaks.

 

[hsfdchief200]

I just looked at my old head gaskets. They can't be installed upside down. The holes in the gasket for the head studs don't line up.

I'll do what you suggested tomorrow and see what happens.

 

[73m819]

the sleave mite be to far down or not far enough, after installing the sleave did you check the deck hight

 

[cranetruck]

Air in the coolant? How did you refill the cooling system? It hold 8 gallons when you include the radiator. Thermostat open. Water/antifreeze mix?
Get a thermometer....

 

[ajg6989]

a handy tool to have for finding temperatures on a running engine is one of those non contact laser temperature readers got one from harbor freight for $49 works great can read temp at each hose each cylinder anywhere on the engine.

 

[hsfdchief200]

I drained 5 gallons out of the cooling system when we did the engine work. When I refilled it, I removed the pipe plug on the side of the intake manifold to let the air escape. Is there somewhere else to bleed the air out when filling the cooling system?

 

[hsfdchief200]

Pull the alternator belt off. Fill the rad. all the way to the top of the filler neck (engine cold). Leave the rad. cap off. Start the engine and watch the water in the rad. If you see bubbles, or water starts pushing out in the first minute or so, you have a compression leak into the water jacket. .

I tried this today, except that I didn't fill it completely to the top. I left it where it was, a little above the yellow full sticker. It ran for about 5 minutes before it started getting hot. There were a few air bubbles at this time when it was getting hot. Also at this time the water level rose to the top, so the thermostat had opened. I think that's where the air bubbles came from, too. There were no air bubbles or high water level just after the engine started. It took about 5 minutes.

The top of the radiator kept getting hotter, but the water level never went down or changed any. When I shut the engine off, I felt of the lower radiator hose, and it was very cold - not even warm at all. The bottom of the radiator was also very cold with no sign of any warmth.

So I'm thinking it might be the radiator. It may be stopped up. The one thing that we forgot to do the other night when we were rushing to get it running was to flush the radiator. A number of the fins were damaged by the fan years ago (before we got it), but there are no leaks anywhere.

I know where an M49 is that has a good radiator that I can get. Does that sound like the problem?

 

[rmgill]

If part of the radiator is either blocked or full of crud then it could seriously mess up the cooling capacity of the engine. Early on in my learning mechanical things, I replaced the radiator in my '76 Monte Carlo. Good hoses, good water pump, new radiator, new thermostat. It would after long running overheat in the summer. I couldn't figure out why. I was starting to wonder if the engine had a serious issue. I replaced the radiator on a lark with a larger model. Lo, it worked. Turns out the radiator I had initially used was for a 350 ci engine. In spite of what several mechanics had said when I was getting it serviced in highschool, it was a 400 ci engine. Only my close scrutiny of the engine clued me in to that.

Try flushing the radiator if you can.

 

[cranetruck]

The time to operating temp (approx 170) may take 1/2 hour on a summer day. At idle, the the engine may never reach a high enough temp to open the T-stat, which will start to open at 185F.
If you have a winter cover, it may reach 180 in 1/2 hour at fast idle (1,200 rpm or so) and the T-stat will begin to open.
I still say, get a thermometer.

 

[73m819]

was the engine doing this before the piston change

 

[hsfdchief200]

I can't honestly say if it'd done this before or not. I just got the truck at my dept. a few weeks ago. I'd only driven it about 1/4 mile before all of the timing issues/blown head gasket, etc. It did get hot then. But now that has all been straightened out.

The water pump is turning. After it gets hot and the water is overflowing, it will gradually go down after the truck has set for a few hours or overnight. That makes me think that the radiator isn't letting the coolant flow quickly enough when the engine is running.

I pulled the radiator out of the M49A2C this afternoon and gave it a thorough cleaning, inside and out. The fins on it are definitely in better shape. I'll put it in the M35 tomorrow and flush the cooling passages in the engine.


re: the sleeve. The one that I took out of the LDT-465 in the M49A2C was identical to the other ones in the LDT-465 in the M35. It went all the way down and was flush with the top of the block just as the others were.

 

[mendo069]

overheating

sounds like the radiator to me... my truck had a similar problem, minus the head issue.. took to radiator shop and they took mine apart and rodded it out to clear all the clogged tubes... man there was all kinds of junk in there... now she runs cool, with no issues ever since.. here in cali it cost me $150.00... but well worth it.. good luck...mendo

 

[hsfdchief200]

Well the problem appears to have been the radiator. I installed the M49A2C's radiator and water pump (the M49A2C had an '88 Hercules engine vs. the '68 Continental in the M35A2, so most of the tanker's parts were in better shape). The impellers were slightly longer in the newer pump, so that's the one I used.

We let the truck run near 2000 RPM for about 20 minutes. Never once did the water level rise and overflow like it previously had. It took considerably longer for the top of the radiator to warm up because the water was flowing through the radiator like it should. The bottom of the radiator was even a little warm. So the newer radiator is obviously flowing much better. Water never spewed out of the radiator cap.

The temp gauge also deciced to start working. Go figure. It never got above 160. I'll be able to tell for sure what it's going to do when I drive it tomorrow. So far it looks promising.

 

[Desert Rat]

HSFD,

I was going to say check out the impellers on the pump. Many times this is overlooked in a cooling system. I've seen many people frustrated with overheating problems due to worn out impellers and looking for more expensive solutions.