running hot

[mikej]

can anyone help? I have a 2.0 merc 150 that runs hot at rpms above 4500. when i run the motor below 4500 rpms the temp is around 120-140. as soon as the motor spins up the temp will jump to 180. i have gutted thermostats, removed the popet valve and there is 18 lbs of h2o pressure. i have checked for corosion in the block and everything looks fine. any help would be appriciated.

[Talon2.5]

i had the same problem a few months ago and it turned out the water pump and waterpump base were warped and leaking as well as bad sealing on the brass tube where it inserts into the pump, it would run cool until i got on it and would heat right up, mine also had a lazy piss tube and would take a while to dump water when ya started it, now it runs cool as a cucumber :cool:

skip

[DaveR]

You may just be too lean. If it's carb go up a couple sizes.

[mikej]

Thanks for the replies. I have jumped up 2 jet sizes from stock and I replaced the housing on the waterpump the last time i put a water pump in. The motor still runs hot. I dont know what to check next...........:D

[Tony Brucato]

Did it just start overheating or has it been like that since the gutted thermostats and removed poppet valve?

[us1]

Good question Tony. Also Where are you taking this temp measurement, is it water temp or head temp. Have you checked the accuracy of the gauge with a thermometer on the pee tub?

[mikej]

I pulled out the popet valve and removed the thermostats trying to make it run cooler. I am taking the temp from the head not the water. I have also checked the guage by heating water in a pot and placing a cooking thermometer and sending unit in the pot. they were within 5 degrees of each other.

[DaveR]

Leaving the thermostat housings empty is not a good idea and could make it run hotter. Put ss washers with 1/8" holes in place of the themostats to make sure the water stays inthe block long enough to transfer heat.

[us1]

Dave is totally right to get the head cooler you need to run 1/8 fender washers in the thermostats, you are dumping way to much water before it get through the heads. If that is your head temp not water temp it sounds fine to me. I always run water temperature gauges not head. Water temp after a run should be 110 degrees. I belive the head temp should be about 180

[Talon2.5]

hey john,

when i was going through that same scinerio and was posting about the 2.5 on the 2.4 mid-plate, the reason i was concerned about the water temp was because when i ran lower rpm's it was 140ish and then when i let it run out at 180-182ish degrees this is what happened to the first powerhead, and thats why i tore back into the new one i built (found all that stuff with the pump and tube) so it wouldnt happen again and found all that stuff bad in mine, and his sure sounds like what i was going through and i have the 1/8 hole washers and poppet setup that way too, finally she's running cool, i'm gonna install the water temp guage as well as head temp guage, that 180 scares me, and you can see why !! i know you know your stuff!! but i'm gunshy now on that 180 deg.

just my thoughts on it, skip

this came out of #1 cylinder and devistated the block too

[us1]

Skip I think your talking about cylinder temperature not water temperature. Water temp should never go over 110. As I said before I only run water temp gauges, the sender must touch the water not just sit on the outside of the head. From what I have heard though a cylinder head temp of 180 is not that uncommon.

[mikej]

I have tried using the 1/8 washers in place of the thermostats and it made it run hotter. This is why i am so confused on why it keeps getting hot. thanks for all the help.:p

Could be a head gasket leaking into the water jacket. This will cause superheated water and steam creating hot spots. An exhaust chest gasket leak can cause the same. I have seen head gaskets leak compressed exhaust gas into the water jacket area as the pressure of the heated gas is much greater than the water pressure. high pressure gas will go where water won't. No a compression check won't always show it. A pin hole in the exhaust baffle(usually caused from corrosion will do the same.
Eagle One

[WillyT]

Did your "corrosion check" include the little water flow holes that are under/hidden by the "exhaust plate" between the cylinder banks? My 150 had all of the same symptoms and the fix was to take off the exhaust plate and clean out the holes with a hand-held drill bit (about 3/16" or so). Can't remember for sure, but I think there were 3 or 4 holes back there that were each filled with corrosion products. Ran cool after that for many years, even with NOTHING where the thermostats used to be (I did not know about the "washer thing" in those days)! Sold engine (still running well) after 22 summers of use!

[Talon2.5]

mike,

i would deffinately check what the others have posted!!!!!!! i forgot about a 2.4 i had with bad head gaskets and blockage like willy T mentioned


skip

[us1]

I’ve got to ask this question. If we are talking about cylinder temperature not water temperature, and I am assuming we are, how cold are you trying to make this thing run?

[mikej]

thanks for all the great advice. I was told that 180 head temp was to hot. I have never had the heads off of the motor. If they were leaking would you be able to tell by looking at the plugs? Where exactly is the exhaust Plate. :cool:

[us1]

One thing to keep in mind is it’s a 2.0L which has ½ thick steel sleeves, this motor will retain much more heat than a Nicasil motor.

[WillyT]

The exhaust plate is the tall fairly narrow plate in the back of your engine right in the middle between the two banks of cylinders. It is held on with several bolts. You will need a new gasket to replace it. Be careful with the bolts since they can break if you are not careful. On my engine, the holes were actually a little hard to find at first because the corrosion (a yellow/white substance as I recall) had filled them level with the surounding surface. This was the first thing my Merc mechanic guru told me to check after all of the normal things had been inspected and found to be ok.

[mikej]

thanks I will try this next

[DaveR]

Go to the by-u-boyz website and check under "Cherry 2.4". There are pictures of the holes and modifications suggested by Prof. O.B. who used to post here.

[us1]

Check out this post for running hot
http://forums.screamandfly.com/showthread.php?s=&threadid=5416&highlight=blockage

[Talon2.5]

dont forget most motors that werent high perf with the poppets already reconfigured did NOT come with the water diverters installed to slow the flow and pull the heat out, so after ya check that stuff in the posts above (and there all good) if ya cant find it, and pull the heads for a gasket check, install the diverters if ya leave the poppet out and the 1/8 washers in, they are simply rubber hose (gasline 3/8 i believe) and go into the area shown in my pic, be sure you cut the length so that it leaves enough room on each end so water can pass by the ends, yet restrict the flow, 1 inch length i believe and they go between cylinders 3 and 5.......and 4 and 6


skip

john, yes i was talking about 180 block temp that scares me as you can see by what happened to me, i havent been back to this thread in awhile, now at an idle in gear she idles well below 130 and runs out around 150 block temp

[us1]

Hey skip there’s a lot a 2.5s running 160 170 and his is a thick steel sleeve 2.0 so I’m not so sure his is really running that hot. What do you think?

[Talon2.5]

any more info on the motor yet? did everything check out? give us an update on what ya found so far, is the divider ok? did ya pull the heads?


skip

[General Joe]

I plan on tearing it apart on monday. I am going out of town this weekend so I wont be able to do it until then. I will keep you posted

[Talon2.5]

ok looks like mikej turned into general joe

mikej 7 posts

general joe 3 posts


hhhhhhhhhmmmmmmmmm


skip