i am searching for answers and some of you have had similar problems
with volvos md7a in the cd30 ...this engine is twenty or so years old ...not many hours in it and seems to run well no oil leaks or excessive oil consumption it idles at about 750/800...but max reving about 2200rpm...may be tired and some work may rejuvenate this thing
my biggest corncern is that it overheats at any speed ...cooling system could be restricted/blocked but i see water flowing out the tail pipe however it aint cooling the engine...can a roto rooter improve this situation and if so how do i go about doing this procedure do i need to take it to a shop for expert/expensive diagnosis and looking at eng removal for overhaul...of course cost not being an issue a new powerplant smaller/leaner/lighter hier hp.s
should do..but thats not feasible at this time and a fix up is what i im looking at....and i ask the members of this board for their opinion..
i know we have great talent and i will be greatfull for it.
.......may have to go to a sixteen foot sculling oar and use the md72 as mooring ...i just cant stop thinking about this possibility...
...anyway folks ...talk to me...thanks...
cheers/mike
compinchecd30@yahoo.com
md7a overheat
Moderator: Jim Walsh
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John R.
Re: md7a overheat
Have it checked for a faulty thermostat. Is the engine fresh or raw water cooled? If it's fresh, check the heat exchanger for blockage. Check your pump impellers for good condition; if a blade is missing that may be the cause, could be blocking a waterway. Make sure your seacock is free from obstruction, same for the hose running to the strainer, make sure your strainer basket is clean.
mike mascaros wrote: i am searching for answers and some of you have had similar problems
with volvos md7a in the cd30 ...this engine is twenty or so years old ...not many hours in it and seems to run well no oil leaks or excessive oil consumption it idles at about 750/800...but max reving about 2200rpm...may be tired and some work may rejuvenate this thing
my biggest corncern is that it overheats at any speed ...cooling system could be restricted/blocked but i see water flowing out the tail pipe however it aint cooling the engine...can a roto rooter improve this situation and if so how do i go about doing this procedure do i need to take it to a shop for expert/expensive diagnosis and looking at eng removal for overhaul...of course cost not being an issue a new powerplant smaller/leaner/lighter hier hp.s
should do..but thats not feasible at this time and a fix up is what i im looking at....and i ask the members of this board for their opinion..
i know we have great talent and i will be greatfull for it.
.......may have to go to a sixteen foot sculling oar and use the md72 as mooring ...i just cant stop thinking about this possibility...
...anyway folks ...talk to me...thanks...
cheers/mike
-
Dale W.
Re: md7a overheat
For the raw water cooled engine: Remove the exhaust manifold. (4 obvious bolts on the front tubing that goes to exhaust canister, 4 bolts on the side of the manifold which are long and go into the block, the tubing from the water pump, and the hose on top).
Then sort of work the thing out and see what you have. The cap with 2 bolts on the back is the thermostat housing. Take it off and see what you have.
The thermostat housing itself is subject to corrosion, clogging, and a variety of shade-tree fixes.
If the hole in the middle is clogged, clean it out.
A more pervasive problem is that the passages cast in this housing tend to react poorly to sitting around for long periods of time in salty water. They sort of disappear. Water moves, but not where it needs to. The jackleg part of the equation is that this $5.59 piece of cast metal substance is available from VOLVO for only $194.00 (last time I was brave enough to ask). Consequently, mine is reworked JB Weld Jr, and other epoxy stuff to both properly mate with the manifold and also flow water right.
The thermostat itself can be an embarassment. The Volvo thermostat at the car store is $5.95, the one from VOLVO will set you back $40.00. I found that I could not 'balance' my system with the new style thermostat, and they stopped making the old one - - BUT the MD-11 thermostat (old style which plugs that hole in the thermostat housing when it opens) works with only slightly enlarging part of the manifold.
Now the manifold: See the gasket and the holes. Only the two square holes are for exhaust, the remaining holes should be clear to pass water around. Check the engine block side to assure that all these water passing holes are clear. (The smaller one at the top between the two square hole was invariably clogged on mine (the area I operate in is silty).
When reassembling, I use the blue Permatex hypolon gasket and flange sealer stuff and I have never had leaking problems.
I have also talked to the tech people at Volvo and they are friendly, knowledgable and even faxed a 6 page treatise that was a useful compendium of ways to fix this fairly common problem.
Part of their deal is assuring a 'balanced' flow through both raw water inlets (the one in the bottom of the manifold) and the one that goes back to the bottom of the thermostat housing). My theory is that by cleaning everything thoroughly and making sure the passages in the housing remained separate (when the housing corrodes, the passage become one - the check is to dig at all interior parts of the housing with a good blade or pick, and if it crumbles, you've found some stuff that needs to be dug out and rebuilt with epoxy or get a new housing).
I found that if I do the above cleaning out about every 2 years I avoid the overheating blues.
This particular task is not real technical nor particularly difficult. I do look fondly at those Yanmars, but the Volvo has never let me down, and it just needs its occasional cleaning.
Good luck, and may better cooling days be yours.
Dale
majortest@earthlink.net
Then sort of work the thing out and see what you have. The cap with 2 bolts on the back is the thermostat housing. Take it off and see what you have.
The thermostat housing itself is subject to corrosion, clogging, and a variety of shade-tree fixes.
If the hole in the middle is clogged, clean it out.
A more pervasive problem is that the passages cast in this housing tend to react poorly to sitting around for long periods of time in salty water. They sort of disappear. Water moves, but not where it needs to. The jackleg part of the equation is that this $5.59 piece of cast metal substance is available from VOLVO for only $194.00 (last time I was brave enough to ask). Consequently, mine is reworked JB Weld Jr, and other epoxy stuff to both properly mate with the manifold and also flow water right.
The thermostat itself can be an embarassment. The Volvo thermostat at the car store is $5.95, the one from VOLVO will set you back $40.00. I found that I could not 'balance' my system with the new style thermostat, and they stopped making the old one - - BUT the MD-11 thermostat (old style which plugs that hole in the thermostat housing when it opens) works with only slightly enlarging part of the manifold.
Now the manifold: See the gasket and the holes. Only the two square holes are for exhaust, the remaining holes should be clear to pass water around. Check the engine block side to assure that all these water passing holes are clear. (The smaller one at the top between the two square hole was invariably clogged on mine (the area I operate in is silty).
When reassembling, I use the blue Permatex hypolon gasket and flange sealer stuff and I have never had leaking problems.
I have also talked to the tech people at Volvo and they are friendly, knowledgable and even faxed a 6 page treatise that was a useful compendium of ways to fix this fairly common problem.
Part of their deal is assuring a 'balanced' flow through both raw water inlets (the one in the bottom of the manifold) and the one that goes back to the bottom of the thermostat housing). My theory is that by cleaning everything thoroughly and making sure the passages in the housing remained separate (when the housing corrodes, the passage become one - the check is to dig at all interior parts of the housing with a good blade or pick, and if it crumbles, you've found some stuff that needs to be dug out and rebuilt with epoxy or get a new housing).
I found that if I do the above cleaning out about every 2 years I avoid the overheating blues.
This particular task is not real technical nor particularly difficult. I do look fondly at those Yanmars, but the Volvo has never let me down, and it just needs its occasional cleaning.
Good luck, and may better cooling days be yours.
Dale
majortest@earthlink.net
-
mike mascaros
Re: md7a overheat...dale w/john r
thank you for your input this is the kind of info i was seeking...
i had changed the thermostat in the past and cleaned the tubing
from the water pump and the thermostat housing and it holes but been reluctant to poke further into the guts of the cooling system...now with some guidance and references will kind of try again and see how much fixing and improvements can be accomplished...
i plan to be working on this project next couple of days and will
post the results ...
again thanks for your help
mike/compinche cd30...
compinchecd30@yahoo.com
i had changed the thermostat in the past and cleaned the tubing
from the water pump and the thermostat housing and it holes but been reluctant to poke further into the guts of the cooling system...now with some guidance and references will kind of try again and see how much fixing and improvements can be accomplished...
i plan to be working on this project next couple of days and will
post the results ...
again thanks for your help
mike/compinche cd30...
compinchecd30@yahoo.com
-
Bks
Re: md7a overheat...dale w/john r
Mike, when I had similar problems with overheating I unbolted the waterbox/manifold and flushed the passages with muriatic acid and this disolved the carbon build up leaving everthing looking like new and ending the overheating problem. One note of caution, be careful not to damage the copper gasket which seals the waterbox to the engine block. BKS
-
brian
Re: md7a overheat
Cleaning the exhasut manifold like others have said should correct the over heating problem.
If your not getting up to max rpm check your filters( primary and fine) the engine might be starving for fuel. Also you may want to pull the injectors and have the spray pattern and cracking presure checked.
pedbed@earthlink.net
If your not getting up to max rpm check your filters( primary and fine) the engine might be starving for fuel. Also you may want to pull the injectors and have the spray pattern and cracking presure checked.
pedbed@earthlink.net
-
John D
Re: md7a overheat
Mike - there is a product out there that I used to clean out my MD7a (raw water cooled) called Marsolve. Check out their website at www.marsolve.com. Might be the ticket - worked for me.mike mascaros wrote: i am searching for answers and some of you have had similar problems
with volvos md7a in the cd30 ...this engine is twenty or so years old ...not many hours in it and seems to run well no oil leaks or excessive oil consumption it idles at about 750/800...but max reving about 2200rpm...may be tired and some work may rejuvenate this thing
my biggest corncern is that it overheats at any speed ...cooling system could be restricted/blocked but i see water flowing out the tail pipe however it aint cooling the engine...can a roto rooter improve this situation and if so how do i go about doing this procedure do i need to take it to a shop for expert/expensive diagnosis and looking at eng removal for overhaul...of course cost not being an issue a new powerplant smaller/leaner/lighter hier hp.s
should do..but thats not feasible at this time and a fix up is what i im looking at....and i ask the members of this board for their opinion..
i know we have great talent and i will be greatfull for it.
.......may have to go to a sixteen foot sculling oar and use the md72 as mooring ...i just cant stop thinking about this possibility...
...anyway folks ...talk to me...thanks...
cheers/mike
John
john_dupras@hotmail.com
-
Ken Cave
Re: md7a overheat
There are two ways in running an MD7A-with or without a thermostat. Take it out entirely and see how the engine performs. If it stays cool, replace it with a new Volvo thermostat.
If you have replaced the impeller lately, did you have all the vanes in place on your old one? If you did not, chances are that is the problem.
New water pumps for the MD7A can be purchased from Marelco out of Seattle for about $140.00 Phone number is 206 545 4224 Ask for Bill when you order. This is a lot cheaper than Volvo will charge-and it is the same pump!!
Ken Cave
bcave@whidbey.net
If you have replaced the impeller lately, did you have all the vanes in place on your old one? If you did not, chances are that is the problem.
New water pumps for the MD7A can be purchased from Marelco out of Seattle for about $140.00 Phone number is 206 545 4224 Ask for Bill when you order. This is a lot cheaper than Volvo will charge-and it is the same pump!!
Ken Cave
bcave@whidbey.net
-
Larry DeMers
Re: md7a overheat
First of all, there is no "Volvo" water pump for the MD7A/B. That pump is a bolt on *Johnson Pump*, which I just replaced for $120 from DiPetro International, a Volvo Dealer in the North East (can give you the address/phone # if interested).
The MD7A/B needs to be run warm to keep up the efficiency. We run a 190 degree thermostat ($47 at the same source..a Volvo part too). Now this is on Lake Superior, where the water temps rarely exceed 70 deg. You may need to install a 180 degree thermostat for the water temps and weather in your area. But I would not recommend running without a thermostat for longer than the testing takes, and that is what the writter seems to be suggesting too. Running too cold a temp will do a lot of damage from carbon buildup, especially in the valve and valve seat area, exhaust mixer elbow and even the piston rings will eventually begin to stick. Keep the temps up in this engine.
Cheers,
Larry DeMers
demers@sgi.com
The MD7A/B needs to be run warm to keep up the efficiency. We run a 190 degree thermostat ($47 at the same source..a Volvo part too). Now this is on Lake Superior, where the water temps rarely exceed 70 deg. You may need to install a 180 degree thermostat for the water temps and weather in your area. But I would not recommend running without a thermostat for longer than the testing takes, and that is what the writter seems to be suggesting too. Running too cold a temp will do a lot of damage from carbon buildup, especially in the valve and valve seat area, exhaust mixer elbow and even the piston rings will eventually begin to stick. Keep the temps up in this engine.
Cheers,
Larry DeMers
Ken Cave wrote: There are two ways in running an MD7A-with or without a thermostat. Take it out entirely and see how the engine performs. If it stays cool, replace it with a new Volvo thermostat.
If you have replaced the impeller lately, did you have all the vanes in place on your old one? If you did not, chances are that is the problem.
New water pumps for the MD7A can be purchased from Marelco out of Seattle for about $140.00 Phone number is 206 545 4224 Ask for Bill when you order. This is a lot cheaper than Volvo will charge-and it is the same pump!!
Ken Cave
demers@sgi.com
-
Ken Cave
Re: md7a overheat
Larry:
I did not say that I was using a "Volvo" water pump!!
The pump I purchased from Marelco was indeed a Johnson Pump, number F35B-9-1035157-3. The two clamps to hold it on are number 01-43238
When I purchased mine last year, the total bill, including UPS of $4.29 was $137.29.
The source is Marelco Johnson Pumps, Seattle Warehouse.
Phone number is 206 545 4224. Bill Tibbits is the person you want to talk to.
As for the thermostat, runing at 190 degrees is way too high for use in salt water!! I use the Volvo Penta Thermostat (No 875796-5) which costs me about $30.00 by ordering from England, and these run around 165 degrees.
Ken Cave
bcave@whidbey.net
I did not say that I was using a "Volvo" water pump!!
The pump I purchased from Marelco was indeed a Johnson Pump, number F35B-9-1035157-3. The two clamps to hold it on are number 01-43238
When I purchased mine last year, the total bill, including UPS of $4.29 was $137.29.
The source is Marelco Johnson Pumps, Seattle Warehouse.
Phone number is 206 545 4224. Bill Tibbits is the person you want to talk to.
As for the thermostat, runing at 190 degrees is way too high for use in salt water!! I use the Volvo Penta Thermostat (No 875796-5) which costs me about $30.00 by ordering from England, and these run around 165 degrees.
Ken Cave
bcave@whidbey.net
-
mike mascaros
Re: md7a overheat
well...I am really pleased and must thank all for your imput into my
question on md7a overheat...the problem has not yet been resolve due
lack of time but i will soon tackle this project with a lot more knowledge ... again thks.
JOHN D
BRIAN
BKS
DALE W
JOHN R
KEN C
LARRY DeMers
please dont stop...Im sure there more opinions/experiences out there.
compinchecd30@yahoo.com
question on md7a overheat...the problem has not yet been resolve due
lack of time but i will soon tackle this project with a lot more knowledge ... again thks.
JOHN D
BRIAN
BKS
DALE W
JOHN R
KEN C
LARRY DeMers
please dont stop...Im sure there more opinions/experiences out there.
compinchecd30@yahoo.com