E38 w 5432 universal A. Overheating

FLokiDk

Junior Member
Hard to say if you have a coolant air bubble big enough to effect heat exchange without seeing a diagram of the layout. But here are some notes to guide things:

The reservoir is an expansion tank designed to allow coolant to expand when hot and contract as it cools without impacting the pressure inside the coolant circuit BEYOND THE LIMIT set by the radiator cap, which is a pressure check valve. That’s usually set by design at something like 8-15 psi. The reason is that the boiling temperature of the coolant is higher under pressure. Beyond that pressure some coolant can escape to the reservoir, and when the engine and coolant cools and contracts, it can be pulled back in, since the cap is also a check valve and only pressure restrictive in one direction.

What that means is, if the hose connections between the radiator cap (on the engine, there is no “radiator” but it looks the same as a radiator cap) -that hose needs to be air tight between engine and reservoir or air can be sucked back into the engine instead of coolant, or if the reservoir has not enough coolant, same thing.

One way to potentially remove air and fully charge the system with coolant is to open that radiator cap so air can escape. If there are any points in the system of coolant higher than the cap, (not counting the reservoir circuit which is often higher) they need to be cracked open too to let the air out. Simply having coolant in the reservoir will not allow it to flow back into the engine because there is some resistance at the radiator cap check valve, it normally gets drawn in by the vacuum of the contracting coolant as it cools off after shut down. Under normal circumstances, several cycles of heating and cooling usually self purges the air from the coolant system automatically, the bubbles escape to the reservoir, come out the top as air, and coolant gets drawn in during cooling phase after shut down. For all that to work, the hose connections need to be air tight and the radiator cap functioning properly, but they rarely fail.

it should be possible to feel the coolant temperature entering and exiting the heat exchanger to see if it’s at engine temperature. If it is, the likely culprit is the seawater flow through the exchanger, either restricted coming into the boat from the through hull, or from bad pump flow through the raw water pump, or a restriction at the mixing elbow. Barnacles, dead minnows, seaweed, can all restrict inlet seawater supply. Easy way to check that is to disconnect the seawater hose going INTO the heat exchanger and start the engine and see how much flows. Should be a lot! If it’s dribbling or something, that’s no good. If it’s a strong flow, the next check is the house OUT of the heat exchanger, since the internal tubes can clog up.
A high point in the sweater hose should not matter if flow level is adequate, the water would just push the air out.

A fairly sudden change in cooling function is most likely a seawater flow issue. I’ve had a little blob of seaweed get stuck in the intake of the through hull and instantly the engine behaves as you describe. Happened to me just this season motoring away from the dock through some floating rotting eelgrass. 2 minutes later I noticed steam in the exhaust, and temp was up around 200, way more than normal. There was flow, but not nearly enough, I had to run very slow to control the temp coming back in. Had a diver clean my intake screen, all was well. Made me want an alternative intake system plumbed in, maybe via the sink drain?

Bottom line, verify seawater flow first, it needs to be really strong flow all the way through to the water lift muffler. The mixing elbow hose (seawater coming from heat exchanger) is another easy place to verify flow of the whole seawater system, but only test that by disconnecting and dumping into a bucket for a couple seconds of course.

My guess is your inlet is clogged, or seawater pump impeller is shot.
The entire raw water system has been checked , cleaned or replaced parts. This works great. But I think it might be a stuck thermostat, gonna try a run without to see if there is a big change just idling. If not it must be the coolant pump I think.

The most annoying thing is... In the middle of the testing the starter suddenly stopped cranking/working... Not even the clicking for not being able to draw sufficient amps to crank... Will have to sort that first now... Feeling a bit unlucky lately.but deffinetly get to learn the engine!
 

FLokiDk

Junior Member
Provided the batteries are good, may be loose and or corroded connections. Check and clean all your high amp cables especially grounds at junction blocks and on the engine ground posts.
I'll go over the thick cables. We ran into yet another problem, outboard wouldn't start... It seems to work now even though it's one of those 'i have no clue why' moments.. anyway, battery for starter was installed seperatly 3 months ago to give us trust in running the starter, so it is most likely not that one, 12,9v measured, I know it does not tell anything about amp draw, but it really only has been used for something like 50 starts and constantly charged, nothing draws on its circuit.

I'm really happy for all input, even though it may seem a bit disappointing that the problem does not get fixed, even for you guys trying to help I imagine.
A question about the grounds between junction blocks, I wasn't certain what you meant there, could be a language/translation issue that confuses me, will you elaborate a bit?

I looked at the starter just now... It seems red positive and a yellow wire connects to the solenoid, but to my surprise the black one seems to go to the side of coolant resovoir... Am I being stupid or is there an explanation behind thar?

Thanks and lots of love and respect for the help to all of you.

Torben
 

Dave G.

1984 E30+ (SOLD)
the black one seems to go to the side of coolant resovoir.
Is it physically connected to the reservoir ? I would think that very odd. I would guess it is not and runs somewhere to a ground stud on the engine or maybe back to the batts. There may be junction blocks on bulkheads in the engine bay, or in the battery compartment, and possibly behind the DC panel. I am not familiar with the wiring on a E38 maybe someone else who is can chime in. There may also be a wiring diagram for the E38 in our resources department.....

 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Ground often installed to coolant tank. Check cockpit panel starter push pull or starterkey unit. Bypass to test.
 

bigd14

Contributing Partner
Blogs Author
Had a similar starter problem on a charter boat. Was advised to gently tap the starter with a hammer to shift things around. Apparently the starter can get stuck in a certain position where it won’t energize. Worked great.
 

FLokiDk

Junior Member
Ground often installed to coolant tank. Check cockpit panel starter push pull or starterkey unit. Bypass to test.
I went through the whole ciruit of the starter/solenoid. Checked engines 'griund... Which as I see it I just how it is bolted to 'hull'/metal structure supporting floors n engine. Did minimal cleaning of where engine is bolted with wd40 and wirebrush. Multimeter showed all good, buy i did not really understand where to measure at the back of keystarter housing. Lots of wires comming and going. Was in doubt if I should turn off both battery system(starter and house) and find a kontinuity test with key turned to cranking.. but then again, if u don't now where to test from/to and fault was there you couldn't create the kontinuity. So I went with that the buzzer did work with turning the key, so even though not a very certain conclusion, I concluded error most likely not there. We decided to go with tapping the solenoid, but I honestly dont know if it just spun up or I hit the solenoid with stick first . But worked it did. Had taken out the thermostat and it was obvious that things worked now, though no thermostat so took long to pick up temp.. all is good except a very tiny drip of coolant from a rather odd place, the left side of engine had a yellow label on it, something with injector pibes. I did hit it one time with a screwdriver adding and stainer, so I guess it could be enough to damage an aging gasket. I'll see if it is possible to tighten the bolts just a tiny bit to start with. But for now we will go sailing now the engine works, we rarely use it except for when we drop anchor.

So we are, most likely good, for now. will look for thermostat, did find a Volvo one but rated 182f. So looking for 165 or close.

Thanks for all the responses
 

JPT

Junior Member
One thing that made a huge improvement in seawater flow and hence cooling on the Volvo 2003 engine in my E38 was adding copious amounts of grease to both sides of the gasket on the seawater pump cover. Before that the temps would often rise to 190 or above, and now the temps are pretty much locked at 175 unless it sucks in a large amount of weed.

Jon
 

JPT

Junior Member
Before adding the grease there was never any sign that water was leaking out from there. However, it's clear now that air was leaking in whenever the engine was running, and thus reducing the pump flow.

Jon
 

Filkee

Sustaining Member
No matter how smart and comfortable you become, it’s very easy to just screw up. Last night I went out with my intake seacock closed. Admiral was messing with the sink before but it was my error not to look for water out the back when I started. Engine sounded funny coming into the mooring and I immediately cut it and ran below to find the error. hoping I didn’t out too many impellar crumbs in the heat exchanger. Had I not brought the snap ring wrench home to fix something else, I’d be out sailing now. So it goes…
 

bigd14

Contributing Partner
Blogs Author
snap ring wrench
Apparently the snap rings aren’t necessary as the cover holds the impeller in place. When I first got the boat I changed the impeller and while attempting to reinstall the snap ring it violently launched into the main cabin, ricocheted around and disappeared. I searched for a while then gave up and replaced the cover without it and everything worked fine until I replaced the entire pump. I found the snap ring about a year later in the bottom of the little storage shelf behind the starboard settee.
 

Filkee

Sustaining Member
Apparently the snap rings aren’t necessary as the cover holds the impeller in place. When I first got the boat I changed the impeller and while attempting to reinstall the snap ring it violently launched into the main cabin, ricocheted around and disappeared. I searched for a while then gave up and replaced the cover without it and everything worked fine until I replaced the entire pump. I found the snap ring about a year later in the bottom of the little storage shelf behind the starboard settee.
This could be a game-changer. Can someone confirm he’s not nuts? Or snap-ringed?
 

Alan Gomes

Sustaining Partner
This could be a game-changer. Can someone confirm he’s not nuts? Or snap-ringed?
He's absolutely right. Where is the impeller going to go?

The front snap ring is necessary for when the pump is off the engine, e.g., when in storage, or for shipping. In that case, the shaft could pull out of the back without the snap ring in place. But with the pump installed on the engine, the shaft is obviously held captive from pulling out the aft end of the pump, and the impeller cannot come out of the front of the pump with the cover in place.
 
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