Possible causes of over heating other than timing / mixture?

[vwjim]

Evening,

I'm a bit baffled so hope someone can give some ideas on what could be causing an engine to run hot.

I'll give some background.

Bus is based in the UK, the owner bought a new 1914cc T1 based engine from the US & had it shipped over here. It was fitted but soon after split either an oil line or a cooler, (I can't remember exactly what the owner said), it was diagnosed as excessive oil pressure by a company local to the owner, so they rebuilt it and fitted it back in the bus for him along with fitting a dual circuit m/c & CSP front disks.

Not many miles later the bus came to me to have an IRS conversion, brake servo & steering rack conversion.

When I started to strip the bus down I began to find some faults with how the bus had been assembled. I'll give you a few of the items found so you have an idea of the quality of the guys who rebuilt the engine (along with the brakes).

CSP brakes had been installed incorrectly and damaged the bearings.
CSP brake pad retaining springs weren't installed.
Front hub nut locking tab washers were missing.
Bugpack style breather box was mounted on it's side so it drained the oil vapour down over the fan.
Rocker cover breather hoses where trapped between engine tinware & bodywork so flattened.
No fuel filter in the tank or in the fuel line.
#1 inlet & exhaust valves tight. #3+4 inlet and exhaust valves loose. NOTE #4 inlet was VERY loose ie around 0.045 thou" (steel pushrods)
Engine case bolt by the oil pump missing, Engine case bolt by at the flywheel end of the engine was missing.
Deep sump mounting studs loose / retaining nuts swimming around in the sump.
Rear gearbox mounts had completely failed so not holding the gearbox at all.
Coil mounted directly to the exhaust

Anyway, you get the idea that the workmanship wasn't amazing....

So earlier in the summer I rectified all the items and also did the IRS / Steering rack / servo / VintageSpeed exhaust. And said the owner should do no more than 500 miles then let me have a look to make sure the engine is okay, (after finding the valve gaps so far out & nuts in the sump I was concerned there might be in internal engine problems).

So right upto date now, and the bus is back here. He'd always said that the oil temp' gauge reported hot oil, like 280 - 320 F but as the gauges and senders aren't from the same manufacturers I was putting those gauge readings to a mis-match of sender to gauge, as the timing is spot on, and if anything its running a little rich.

First job today was to recheck the valves. They're all as they were set 500 miles ago.
Took the oil temp sender out and put it in boiling water to see how it reads on the gauge. Spot on so it isn't the sender giving the gauge wrong info, but is indeed picking up so really high temps....

Did an oil change. 10/40w. Checked the plugs, a little black. Rechecked the timing. Then let the bus idle for a while during which time I watched for leaks & monitored temp' gauge.

The oil gauge soon read 230 F and the dipstick / alternator etc were all too hot to hold. The remote filter head was warm to the touch but not scalding like the alternator / dipstick etc. I'm thinking the sender is pickup up case temps that are elevated faster than the oil within the case.

I've never seen an engine case get that hot on idle before. It wasn't even that warm a day here today.

I don't have any EGT or CHT equipment but you could easily hold your hand in the gases coming out the exhaust. Its got a BDM serpentine type fan belt. Loads of cooling air being blown down over the barrels. It also has a remote cooler supplied by one of those in/out type pump covers.

Sorry for the ramblings, but thought more info you have the better. So, any ideas what could be causing it to run so hot? With so many build errors I'm thinking there is a fundamental issue within the engine, but how to prove it / what tests can be done etc.

Regards.

[FJCamper]

Hi VWJim,

With the engine case that hot, can you touch the external oil cooler? Is it as hot?

My first idea is most of the the oil is not going to the cooler at all.

Do a quick removal of the oil pressure relief valves to see if they're even installed right. If the oil cooler is being bypassed at the valve, the hot oil is being dumped right back into the engine case, then recirculated again, etc., etc.

FJC

[mountainkowboy]

Maybe the wrong fan? Diverter plates not installed? Just some more ideas.

[Piledriver]

Oil pump size?
Oil pressure at various oil temps?

There needs to be a sticky for how the factory oil "thermostat" works.
(hint-it's entirely pressure based, works awesome if everything is stock to the bone)

If the oil pressure is too high, the oil will never really flow properly through the cooler.

[vwjim]

I've not tried to directly touch the oil cooler (stock) but I did get my fingers into the duct at the rear to see if air was passing through the dog-house. There was air coming out which was warm. Though I did think it was quite a low come volume of air but I have never felt that air flow from any engine so have nothing to compare it to.

Will see if another engine does a similar low volume & try touch the cooler itself.

Will also see if the relief plug is in & free.

Also, will check if barrel tinware is in position.

Thanks

[vwjim]

He doesn't have a pressure gauge, well he had a VDO sender & a Mooneyes gauge which read back to front, ie 100% pressure with engine off / low pressure when first start / increasing pressure as the oil warms up. So couldn't get any real data from it, & then yesterday the VDO sender died completely so removed it & fitted a stock sender so at least the dash warning light was working

[vwjim]

Pump size unknown, will see if the owner has a spec'

[vwjim]

Barrels don't have the stock deflectors fitted underneath, instead the have the different design tins, think they're called "cool tins".

[vwjim]

It's a 30mm pump with an "in/out" cover.

[FJCamper]

Hi VWJim,

Are the oil lines off the in/out pump connected to the right in/out ports on the oil filter adapter?

You do need to know the oil pressure cold and hot.

I recommend the factory oil pressure relief pistons -- meaning the solid piston type (front and rear in dual relief cases), rather than the notched pistons.

With a stock cooler, which blows at 120 psi and up, you are apparently not having oil overpressure problems, which is consistent with the pressure relief diverting oil away from the cooler and dumping it back into the case.

FJC

[vwjim]

Thanks. Will fit a temporary set of gauges / senders in & see what it reads.

Then if pressures not normal will pull the relief pistons to check they're even fitted.... Wouldn't suprise me with the other faults I've found.

[vwjim]

Annoyingly everything seemed normal today, in that it didn't do the same high temp's as whitnessed yesterday!

Yesterday, even just letting it idle at home it soon reached 230 F.

Today, fired up and oil pressure when cold at idle was 40psi, at elevated rev's it topped out at 53'ish psi. Oil temps at idle never got over 120 F, (using a Smiths gauge with the sender in the case and a VDO gauge with the sender in an adapter into the stock oil pressure point).

Drove it quite hard around the area up to 65mph then back home and left it at idle while I hooked the temporary gauges back in. Both temp gauges had risen to about 160 F. Pressure at idle had dropped to about 20 psi.

After a little while at idle, the case sensor was reading 180 F, and the idiot light sensor was readying about 160 F.

So today, the high oil temps' weren't recreated while the oil pressure was being monitored.... Maybe the relief valve was stuck before, and today it was working?

[Piledriver]

Pull both pistons and polish them up.

[craigvwdude]

Sounds like that might be a possibility.
Might take it out and give it a good cleaning just to make sure.
Couldn't hurt!

[vwjim]

Cheers guys.