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E38 - Overheating Issue

T

Theanswer

Member I
We have a 1982 E38. Universal 3452 w/ 3,800 hours. We're cruising in Mexico. Water temps 75 degrees. At 1,700 RPM, engine will hold temp at 185 degrees (all temps measured with gun just top of thermostat). Rev. up to 2,100 and over a 5 to 8 minute period it climbs to ~210. Throttle back to 1,700 and she comes back down to 185. Operating temp. of engine is 175 to 190 degrees. I checking intake at hull and it's clear. Cleaned sea strainer. The impeller looks ok, although it's about 500 hours old. Removed end caps of Heat Exchanger and they were clear. Replace zinc anode and made sure there were no broken pieces. Water is exiting boat in what sounds a normal fashion. Shot at mixing elbow with gun and temp. 130. Just a few inches down towards the water lift muffler it's down to 115.

Next step will be to replace the impeller, then have the exchanger cleaned and check out the mixing elbow. Any other thoughts?

Does anyone know the typical volume of water that should be expelling? Looking for any ideas. Thanks.
 
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Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
If the sea water is able to exchange heat with the coolant OK, them I would start to wonder about the coolant itself. Has the block been cleaned out and is the closed-system vane pump in good shape?

Hoses: all recent enough that they are unlikely to have any separation in the inner layers that could cause a partial blockage?

T-stat opens all the way?

......running out of ideas here.....
Class? Bueller?!

:confused:
 
T

Theanswer

Member I
Thanks for the ideas. Yes, if replacing the impeller does not work, I was going to have the exchanger cleaned and replace the coolant. I added probably 1/2 gal and did not dilute it so need to fix that anyway. I am not sure what the, "closed system vane pump" is? The fresh water pump? Hoses were all replaced two years ago when we had the engine pulled and they replaced everything on the engine that needed replacing. Again, thanks for your help.

Loren Beach said:
If the sea water is able to exchange heat with the coolant OK, them I would start to wonder about the coolant itself. Has the block been cleaned out and is the closed-system vane pump in good shape?

Hoses: all recent enough that they are unlikely to have any separation in the inner layers that could cause a partial blockage?

T-stat opens all the way?

......running out of ideas here.....
Class? Bueller?!

:confused:
Click to expand...
 
Loren Beach

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Coolant thoughts

Theanswer said:
Thanks for the ideas. Yes, if replacing the impeller does not work, I was going to have the exchanger cleaned and replace the coolant. I added probably 1/2 gal and did not dilute it so need to fix that anyway. I am not sure what the, "closed system vane pump" is? The fresh water pump? Hoses were all replaced two years ago when we had the engine pulled and they replaced everything on the engine that needed replacing. Again, thanks for your help.
Click to expand...

Sorry for my complicated way of describing the pump that circulates the coolant thru your engine and your heat exchanger. On our old Universal diesel it is centrifugal pump, totally separate from the raw water pump with the rubber impeller. I imagine that it's the same on your engine.
 
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markvone

markvone

Sustaining Member
What size Heat Exchanger?

My 5424 Universal (24 hp) had an original 2 inch diameter H/E for 30 years living in MDR and Santa Barbara. Once I got her to the Chesapeake and our 85 degree water, I had overheating issues. I upgraded to a 3 inch H/E and problems solved. I don't think you can work around the 2 inch H/E with water temps in Mexico like you can up north.

What size H/E do you have?

Mark
 
Christian Williams

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
That seems a lot of coolant to add. Do you have an overflow chamber? Make sure the overflow tube is still there.

Also, it sounds basic, but a newish coolant cap is important. The coolant is under pressure and the cap needs to seal.
 
T

Theanswer

Member I
markvone said:
My 5424 Universal (24 hp) had an original 2 inch diameter H/E for 30 years living in MDR and Santa Barbara. Once I got her to the Chesapeake and our 85 degree water, I had overheating issues. I upgraded to a 3 inch H/E and problems solved. I don't think you can work around the 2 inch H/E with water temps in Mexico like you can up north.

What size H/E do you have?

Mark
Click to expand...

Mark, we have the 3" x 13". Read a few posts indicating there was a 2". I am going to have the heat exchanger cleaned which will allow me to check out the mix elbow, redo the coolant and I'll check there t-stats operations.
 
T

Theanswer

Member I
kmac said:
Could be the thermostat not opening fully.
Click to expand...

Yes...I replaced the impeller on the raw water pump as suggested by our mechanic and same result. I ran another set of test. Just shot the temp at the t-stat every minute at 2100 until it got to 210 then backed her down to 1700 and shot temps until it leveled off at 183. I'm actually leaning towards the T-stat being the culprit. Thanks for the thought.
 
jamescio

jamescio

Member II
Similar overheating issue

I had a very similar problem a few years back...Everything I tried did not seem to cool it down. I had a professional look at the system and was told there was some type of small crack allowing air in the heat exchanger. I did not quite understand how that could happen, I was not losing any anti-freeze or water. But that is my experience with a similar issue if that helps. It was fixed and has been running good since the repair,
 
u079721

u079721

Contributing Partner
Theanswer said:
Yes...I replaced the impeller on the raw water pump as suggested by our mechanic and same result. I ran another set of test. Just shot the temp at the t-stat every minute at 2100 until it got to 210 then backed her down to 1700 and shot temps until it leveled off at 183. I'm actually leaning towards the T-stat being the culprit. Thanks for the thought.
Click to expand...

Yup, my next step would be to remove the thermostat, hang it from a wire in a pot of water on the stove, and note the temp at which it opens fully (if at all?).
 
T

Theanswer

Member I
u079721 said:
Yup, my next step would be to remove the thermostat, hang it from a wire in a pot of water on the stove, and note the temp at which it opens fully (if at all?).
Click to expand...

Thanks for the suggestion. I did get the Tstat out...only issues is loosening the bolts to the housing, one was fairly corroded and sheered off. Hope I can heat it out or stuck with a tap/dye. Will replace with a 160 degree unit as we are in Mexico and water temps are 75.
 
E

e38 owner

Member III
I had similar issue. Thru hull screen was getting clogged. Removed screen added forespar water basket many years ago. Another time had carbon in exhaust manifold at top of u. Cleaned out improved water flow. At the same time replaced exhaust hose. Would swell and impeded flow
 
Christian Williams

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Another time had carbon in exhaust manifold at top of u

Curious if this condition reduced the exhaust water flow enough to notice. It would be useful if we could take that as a troubleshooting sign.


 
markvone

markvone

Sustaining Member
Keep the 180 degree thermostat

The temp setting of the thermostat has nothing to do with engine overheating. Check it's operation to make sure your current thermo is not stuck/not opening fully or swap to another 180 thermo for a test. I did have a stuck thermostat that caused the 5424 in my last boat to overheat as soon as it warmed up. When I checked it in a pot of boiling water it never opened. Fixed with new thermostat.

Universal says the operating temp should be 175 - 185 (why do they only sell a 160 degree thermo?), so keep your 180. It will let your diesel live a longer, happier life.

Mark
 
Navman

Navman

Member III
If all checks out OK with the engine and components then check the prop size and pitch. This is an often overlooked causation which can and will cause overheating at the lower RPM's. I have changed out EVERYTHING including the entire exhaust system and still cannot get above 1950 rpms without overheating, 1800 being optimal for crusing. The only item I have not changed out is the exhaust elbow / manifold which is next on the list. I can run all day and with no current stay at 7 knts. without over heating, but any adverse current and or chop my speed drops significantly. This is exactly when you want to be able to rev it up, which I cannot currently do.

Good Luck!!!
 
Lawdog

Lawdog

Member III
I had similar problems with my E38. No problems at lower rpm, but overheating as rpm increased. I changed the thermostat first, and this is a cheap and easy fix most times. My thermostat was only $6.73 with tax, at NAPA car parts place, instead of the usual $40-60 at marine supply store. However that didn't do the trick, so I retraced the entire cooling system, and discovered that the raw water intake was stopped down with an extra connection above the throughhull, and did not allow it to flow at full capacity, thanks to PO. I dont know why he did this, but I changed the ball valve from the through hull to the proper, open amount, and immediately resolved the problem!
 
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