D24 - Can't solve temperature problem

[Maciek4530]

Hi! It's my first post on this forum! First at all - sorry for my english!

Since March 2024 i own my first 240 with Diesel (i have B230 and PRV one too).

I bought this car very cheap from guy i know since 2018 ( i meet hime maybe 4-5 time since then). Car is beaten up 240 from 1992 (wagon) with D24 and M47. No sils, some rust and headgasket problem at 503 599 km

Between March and August i menaged to send head to service (clean, repair, surface, pressure test).

Car was sitting about 1,5 year with some water on cylinder one, cooling system was mostly empty but leftovers was probably tap water...

I clear most of gunk, remove radiator and flush, remove all pipes, hoses and parts from engine.

I buy new: filters (air, fuel, oil), new drain plug, new headgasket Victor Reinz (1,6mm), cylinder head bolts, new engine mounts (both), new transsmision mount, new exhaust ( downpipe, straight pipe),oil sender, glow plugs, tensioner (roller), both timing belts, alternator and power steering belts, fresh oil (7L - 10W40), front seals, intake, exhaust gaskets, nuts, injectors heat shields, front and rear temperature senders (FAE 32110 x2), water pump (Dolz A154) and of course thermostat (Volvo 273728-> Vervet Carlostat TH5111.88J - even if numbers said it's 88C, in package comes 87*C - so it's stock temperature)

After 3 months of rebuilding engine, 3 trys to start it (i left pump in place - previous owner set it so good that car don't smoke, have power and start in 0,5sec) i find out my problem was timing belts. after that car start like new and drive by itself. I put demiralized water in coolant system to make few flushes and use radiator cleaner at first test drive.

Brake took me 2 mmonths but i rebuild them from basic (dust shields, alipers, pads, disc, brake lines, brake pump rebuild, clean old brake fluid, new parking shes etc + stabilizer bushings, links.

After that car was ready to road test and first bleeding the cooling system.

My first drive was terrifying... suspension doesn't exist, steering wheel have a lot of play ( I mean A LOT, never see something like that).

But here comes my cooling system problem:

After 20min of drive car temperature reach "normal" temp on gauge, i check coolant level and lower coolant hose was cold, same with water in coolant reservoir.

After some more diriving temp just drop below zero, then reach red line in 1 min. Next thing was gauge on "normal" temperature for a while and thean reach alomost red line at my way back home but don't reach it - gauge stay ther until i shut off car.

All coolant hoses: upper, radiator, to and from heater, next diesel pump was warm but lower one and reservoir was still cold (maybe some heat from engine).

I aske few people about it - thei said: change senders to old ones (i call old owner to ask about temperature before headgasket - was good, always around "normal") and bleed system like greenbook says. I do that and left my home.

I remove and check new thermostat in pot. It opens like it should i think.

Tepmerature reach normal temperatur and stay ther.. until i drive uuphill for about 1 min. 2-3 mins after that temperature get higher and sit just under red line. I stoped car and check hoses agine. Same situation. After 3 min of idle temp back to normal. So i try more and more: hard driving and uphill make car hotter but always just below red. After 1h of driving at local roads finnaly i could feel hot on lower hose but there was problem with temp.

Next day i flush whole cooling system with hose (like greenbook says) - remove a lot of brown water (there is some rust still there). Put fresh demiralized water - still same situation. Normal driving on flat, downhill: normal temp stays, some driving uphill and temp get under red line.

So i cut old thermostat (removed inside) and start driving. All hoses (upper, lower) are a little warm, there is warm inside too - temp gauge at 1/4, half way to "normal" when driving - uphill, downhill. After another stop temp start to reach slowly to "normal" temp but there was 1-2mm to get there. Driving lowers temp to 1/4 of scale. That's all.

What i'm missing?

Wrong thermostat? What make and model you used in your D24 to make car stock - 87*C? Maybe i'm buy wrong one? With Volvo number i get a Carlostat TH5111.88J - "88" in name but inside was 87C carlostat.

I find some mahle 87C one with VW numbers but can't crossfit them to volvo numbers...

I don't touch VE pump, car don't smoke, drive fast, there is no overheating (never reach red line), there is hot air inside, i can ride it 1,5h without weird noises, problems etc but still can;t have " steady" temperature like in my B230 from 91.

Maybe it's normal for D24 engine?

Maybe it's demineralized water? (lower boiling temperature)?

New ones temp. senders were wrong ones?

What could be wrong..?

It's supose to be my cheap winter beater but right now i waste 2 times more on engine and brakes then to buy this car witohut sills, some holes in floor, destroyed suspension and steering...

I hope nothing major is happenind - i want to save another 240 in my life (it's 6-th one in my life) and finnaly put some high quality coolant to save it from below 0 temperatures that comes in few weeks.

[DieselScout]

87c thermostat is correct. 80c can be used as a band aid, but won't necessarily fix anything.

Did you flush it with a cleaner or just water?

I had a similar problem in the past.

Most of it was fixed after redoing the cooling system.
New fan clutch, radiator, hoses, thermostat, water pump, multiple coolant flushes, etc...even replaced the firewall coolant port and the heater core valve.

Is the radiator original to the car or relatively new?

[ngoma]

Cold lower radiator section and lower radiator hose point to either clogged radiator, bad thermostat (or incorrectly installed?), or waterpump. Possible trapped air bubble?

NOTE: Running without thermostat can be counterproductive. The correct thermostat has a disc that extends to block the coolant recirculation port as the coolant heats up. If the recirculation port is left open (no thermostat to close it) this reduces the overall flow of coolant through the radiator.

Correct thermostat looks like this:
Example photo.jpg

Can you get an IR thermometer and take readings of the:

1. Upper radiator
2. Lower radiator
3. Left side radiator tank
4. Right side radiator tank
5. Upper radiator hose
6. Lower radiator hose
7. Cylinder head front, rear
8. Thermostat housing

Results should help us find the problem.

[Maciek4530]

Hi! Thanks for answers!

DieselScout - yep, 87*C should be good but i find out that model i get is looking similar to OEM ones but have diffrent details - maybe got other size of hole, disc and flow characteristic. I spedn 3 hours looking for thermostats.

I find out that allegro.pl (kind of polish ebay) show wrong thermostats if i put Volvo number. After some serching i finnally buy new Wahler 4088.87D - that looks like thermostat that was install in factory (i compare it with my firend 79' 244 with sized D24 - very early engine, "A" stamp next to head number, 10 alley key head bolts () )

First i flush it with tap water, then put demineralized water - after brake job i put radiator cleaner, drive it like i write in 1 post, then agine flush with tap water - now it have demiralized water and radiator cleaner. Water looks way better then 6-7 days ago when i start to driving this car.

I don't have fan clutch - it's stock fixed fan drives by belts.

Radiator is discounted in my country last few years - last time it was avilable cost llike 1/3 of purchase price of this car. Old one i have don't leak, i flush it few times and when i touch it looks like it works (next to upper hose is hot, next to lowe hose is cold or almost cold.

I need to wait for new Whaler thermostat i think, i don't know if it helps but probably take me closer to find out what's going on.

ngoma - nothing is cloged, i check few times and do a lot of flushes, thermostat is instaled correct (i saw DieselScout video 10 times and check greenbook about D24 ) but i think i buy wring moodel with correct temperature - maybe flow is different or gap when it's open.

Ye, running without thermostat was a test - now i know that car doesn't reach above "normal" temperature without thermostat so it looks like it's my problem. Like i said 2 times above - i think it could be case of wrong thermostat model.

I don't have IR thermometer so it's last thing i could do.

Old thermostat - looks like Wahler ones, 87C stamp, smal holes on disc

old-1.jpg
old-3.jpg

"New" one - Carlostat, 87C stamp - Vervet Carlostat TH5111.88J - probably wrong thermostat even if allegro show it is Volvo 273728

new-wrong-1.jpg
new-wrong-3.jpg

[Maciek4530]

Whaler 4088.87D - i buy it because it looks like first install one and numbers match finnaly. It should be at my hous at friday. 87C

wahler4088.87D - 1.jpg
wahler4088.87D - 2.jpg

NOS Volvo 273728 from box:

3b786f6a492cb3416a46a27fb200.jpg
55a94ed5495f9425041ef40139e7.jpg